Hoeg. Kaare-1993

A s p h a l t i c C o n c r e t e C o r e s for
Embankment Dams KAARFHÖEG
1 ?i^- ^Q9'3
I
//cA/d. /dicâc,
Asphaltic Concrete Cores

for
Embankment Dams
Asphaltic Concrete Cores
for
Embankment Dams
Experience and Practice
KAARE HÖEG
Statkraft
Veidekke
Norwegian Geotechnical Institute
1993
Printed i Norway
by StikkaTrykk,
Asker og Bierums Budstikke,
BMlingstad 1993.
Cover plioto: Berdalsvatn Dam.
ISBN 82-546-0163-1.
Preface
This book describes Norwegian and international experience and practice with the
use of asphaltic concrete cores for embankment dams.
The properties of asphaltic concrete can, within fairly wide limits, be tailored to
satisfy specific dam design requirements. This is an important aspect and advantage
of using bituminous cores in embankment dams. The additional costs of achieving
special core properties, by for instance increasing the bitumen and/or filler content,
must in each case be compared with the potential benefits in terms of safety and
reliability.
Bituminous cores may be built by different construction procedures, for instance by

the "stone-bitumen" method or "flowable asphaltic concrete" utilizing formwork and
hand placement (Chapter 2). However, the most common procedure used so far is
compacted dense concrete employing special machinery but no formwork. The
central core with the filter/transition zones on either side are placed simultaneously
in one operation. It is the latter method which is emphasized in this book.
Chapter 4 describes modern construction equipment and procedures, and Chapter 6

presents design recommendations for embankment dams with asphaltic concrete core.
Chapter 7 discusses contract and work specifications using as a case study the
Storglomvatn Dam, 125 m high and presently under construction in Norway.
The book is a result of a research and development project which summarized and
evaluated available experience and expanded the know-how through experimental and
analytical studies. The sponsors of the project have been:
The Research Council of Norway (NFR)

A/S VEIDEKKE
STATKRAFT SF (The Norwegian Energy Corporation)
The Norwegian Geotechnical Institute (NGI)
Their financial support and permission to publish the results are gratefully acknow-
ledged.
Chapter 4 is authored by Helge Saxegaard, Leif E. Karlsen wrote the section on con-
tract specifications in Chapter 7, and the NGI dam engineering group contributed
throughout the study.
Oslo, September 1993

Steering Committee for R & D Project:
Svein Huse, Chairman
Kaare Hoeg
Leif E. Karlsen
Helge Saxegaard
5
Contents
Preface 5
Chapter 1 Norwegian Dam Building - Historic Review 9
Chapter 2 Merits of the Asphaltic Concrete Core Design 13

2.1 Introduction 13
2.2 General merits of the asphaltic concrete core 14
2.3 Core construction procedure 15
Chapter 3 Norwegian Dams with Asphaltic Concrete Core 17
Chapter 4 Norwegian Construction Equipment and Practice 29

4.1 Asphaltic concrete plant 29
4.2 Core paving equipment 30
4.3 Placing and compaction procedures 33
4.4 Quality assurance and control 36
Chapter 5 Case Study - The Storvatn Dam 37

5.1 Dam design 37
5.2 Construction and control of the asphaltic concrete core . 42
5.3 Predicted and observed dam performance 44
5.4 Predicted seismic response 49
Chapter 6 Design - Principles and Requirements 55

6.1 Design analyses 55
6.1.1 Typical core design 56
6.1.2 Filter/transition zone 58
6.1.3 Supporting shell 59
6.2 Asphaltic concrete mix design and properties 60
6.2.1 Aggregates and filler 61
6.2.2 Effect of bitumen content and viscosity 65
6.3 Laboratory testing of asphaltic concrete 67
6.3.1 Marshall method of mix design 67
6.3.2 Triaxial testing 67
6.3.3 Permeability testing 68
6.3.4 Resistance to cracking under flexure 69
7
Chapter 7 Construction - Contract and Work Specifications 71
7.1 Contractual aspects 71
7.1.1 Basic contract considerations 71
7.1.2 Prequalification, quality assurance and control . . 72
7.1.3 Price adjustment 72
7.2 Work and material specifications - a case study 73
7.2.1 Asphaltic concrete mix design assumed when
preparing tender 73
7.2.2 Modifications to basic mix design proposed
by contractor 74
7.2.3 Prequalification of contractor 75
7.2.4 Test production and placing of asphaltic concrete
on site 75
7.2.5 Requirements to plant and equipment 75
7.2.6 QA/QC and reporting during construction 76
7.2.7 Requirements to core placing and compaction
procedures 78
7.2.8 Requirements to filter/transition zone 80
7.2.9 Unit prices 80
References 82
Index 85
8
Chapter 1
Norwegian Dam Building - Historic Review
Hydropower is one of Norway's major natural resources and has come to mean more
to Norway than to possibly any other country in the world (Hveding, 1992). When
the technologies for producing and using electricity on a large scale emerged in the
second half of the 19th century, Norway was in a process of rapid industrialization.
With no coal of its own, except at the arctic island of Svalbard, it took quickly to
harnessing the power of its rivers. What got Norway off to a strong and early start
was, more than anything else, the favourable distribution of its hydropower re-
sources. There were sites suitable for development throughout the country.
Even in overall terms, this country of little over 4 million people ranks with the
world's top hydropower producers. In contrast to most industrialized countries,
Norway still has hydropower resources yet to be tapped, enough for another 20 - 30
years of development. Technologies need therefore to be maintained and constantly
updated.
To create high heads for hydropower, most dams are sited in regions where long
winters and poor accessibility must be dealt with (Fig. 1.1). As a result, climatic
conditions and logistics have significantly influenced their design and construction.
Fig. 1.1 The Blasje reservoir in mountainous West Norway
9
The first large dams in Norway date back to the 1890s, and now (1993) there are
290 dams exceeding 15 m in height. Mass concrete or masonry were the main
materials used during the first 30 to 40 years. Then, with the advance of reinforced
concrete, gravity dams were succeeded by slab-buttress dams of the Ambursen type,
and later by reinforced arch dams. These types of dam were predominant during the
period 1930 to 1960.
Systematic construction of embankment dams, mainly rockfill dams, began in 1924,

and now 174 of the 290 are embankment dams of various types (see Table 1.1).
Moraine or glacial till, a broadly graded mixture of stones, gravel, sand, silt and
clay, is to be found in the vicinity of most dam sites in Norway. This was therefore
the first choice for impervious core material, and the zoned rockfill dam with
moraine core dominated the period between 1960 to 1980 (Fig. 1.2).
Table 1.1 Norwegian embankment dams higher than 15 m per September 1993
- statistical summary
Height above Length Volume Comple-

lowest core of of tion
Dam Impervious Number foundation crest dam year
type material of (m) (m) (1000 m')
and element dams
first dam
mean max mean max mean max last dam
Rockfill 1956
Moraine core 111 40 145 361 3400 578 5750 1993
Crushed soft-rock
1966
core 1 17 100 23
1930
Concrete core 9 21 31 154 400 46 135 1974
Asphaltic concrete 1980

core 7* 51 90 641 1472 1884 9515 1990
Scone-bitumen 1981
core 4 24 34 199 339 151 280 1984
1956
Wooden deck 3 41 52 643 970 448 860 1959
1924
Concrete deck 25 25 55 184 460 87 495 1986
Asphaltic concrete
64 1963
deck 1 240 357
Earthfm 1964
Clay or silt core 2 16 17 408 640 168 212 1970
1959
Moraine core 11 27 43 389 820 218 731 1974
Plus two under construction (see Table 3.1)
10
This dominance lasted until around 1980 when asphaltic concrete core walls were
adopted for three rockfill dams in the Aurland scheme. These dams were built very
high up in the western mountains, in locations where only scarce deposits of moraine
could be found, and where severe weather conditions and deep frost (approaching
permafrost) would have hampered the construction of earth cores. Furthermore, for
environmental reasons, the planners wanted to avoid scars in the landscape caused
by earth borrow pits.
Fig. 1.2 The Svartevatn Dam (129 m high) with moraine core under
construction
The highest embankment dam in Norway was completed in 1987: the 145 m high
Oddatjorn Dam with a moraine core. The Storvatn Dam (90 m high, 9.5 mill, m-')
with an asphaltic concrete core was finished the same year. Norway's highest arch
dam, the Virdnejavre Dam (145 m high) on the Alta river, was also recently com-
pleted (Fig. 1.3). However, since 1965, four out of five new dams have been
embankment dams. Presently two rockfill dams are under construction, Storglom-
11
vatn (125 m high) and Holmvatn (56 m high), both with vertical asphaltic concrete
core.
The design and construction of rockfill dams, primarily based on Norwegian experi-
ence and practice, was recently presented in the book by Kjaernsli et al. (1992). The
performance of these dams has, in general, been very satisfactory.
Fig. 1.3 The Virdnejavre Arch Dam on the Alta River, under
construction in 1987
12
Chapter 2
Merits of the Asphaltic Concrete Core Design
2.1 Introduction
ICOLD Bulletin 84 (1992) presents, in chronological order from 1948 to 1991,
the exisfing embankment dams built with bituminous cores of different types, hand
placed and machine placed.
A construction procedure which has been successfully applied in Norway on several

dams, is the stone-bitumen method. The core consists of uniformly graded, crushed
stones or pebbles impregnated to void saturation with bitumen. Metal sheet shutter-
ing is used along the sides of the core wall, which is built in consequtive horizontal
layers 0.2 - 0.3 m thick. The layer form is first filled with clean and dry stone
material which must be accurately levelled over the entire length of the layer before
hot bitumen is pumped in from a heated tank. To avoid entrapment of water or air,
the filling of bitumen starts from one end. The hot bitumen flows forward as an
advancing slope, and the hose nozzle is moved in small steps to ensure that the voids
are filled to saturation.
With a stone-bitumen core the adjacent filter zones become of special importance as
they must be impervious to bitumen. The filter must be of such consistent fineness
and compactness that bitumen cannot be squeezed out at any point by the water
pressure (Haas, 1983).
The reverse procedure is to vibrate gravel into a bituminous mastic filled in between
shutters along the sides of the core wall. This method is considered to be less
reliable and has therefore not been practiced in Norway.
The first embankment dam with a machine-compacted dense asphaltic concrete core,
was built in Germany in 1962, and since 1970 almost only such cores, compacted
in thin layers, have been used in large dams. The procedure does not require the use
of shutters. It is this method, with a bitumen content in the vicinity of 6% by
weight, that is the focus of attention in this book.
As a variation on the methods mentioned above, a different technique is presently

being used in Russia for three large embankment dams under construction (Moiseev
et al., 1988). The dams all rest on deep, compressible, alluvial deposits, which may
cause large differential settlements and distortions in the dam body. The asphaltic
concrete mix, with a bitumen content of 10 - 12%, is poured into 1 m high steel
shutters positioned on top of the previous layer. The shutters are removed as soon
as the asphaltic concrete has cooled down to approx. 45°C, and then the gravel
filter/transition zones are placed. The asphaltic concrete, which is supersaturated
with bitumen (termed "flowable" concrete), cannot be effectively compacted. The
main reasons for using this technique rather than leaner, compacted asphaltic
concrete, are the extremely cold climate and the extra core ductility required at these
13
sites. Furthermore, the technique does not require any specialized placing and
compaction equipment for building the core.
2.2 General merits of the asphaltic concrete core

In about 70% of the 174 large Norwegian embankment dams, a core of morainic
material has been chosen (Table 1.1). However, a core wall of asphaltic concrete
has been found to be a very attractive option, and in the past decade this method has
come increasingly into use with excellent results. As opposed to earth materials,
asphaltic concrete is man-made, and its controlled properties can be tailored to
satisfy specific design requirements.
Since 1978, when the machine-compacted, asphaltic concrete method was first used
in Norway, the equipment and placing and compaction techniques for the core and
adjacent filter/transition zones have been greatly improved. The unit costs have also
steadily decreased, which now makes this a competitive alternative even when mor-
aine material is locally available. Furthermore, potential scars in the landscape from
large earth borrow pits are avoided.
Compared with an earth core, the placement and compaction of asphaltic concrete
is much less susceptible to adverse weather conditions. This enables the contractor
to extend the working season and to conduct an almost continuous operation, keeping
the construction on schedule. While rainy weather rarely causes difficulties for
asphaltic core construction, snow and sub-zero weather limits the construction season
to about 5 months in the Norwegian mountains. This is approximately one month
longer than that available for moraine core construction
Asphaltic concrete is virtually impervious, flexible, resistant to erosion and aging,

workable and compactable, and offers jointless core construction. When the asphal-
tic concrete mix is properly designed, its viscoelastic-plastic and ductile properties
provide a "self-healing" (self-sealing) ability, should cracks develop in the core wall.
Asphaltic cores are therefore very well suited for dams in earthquake regions, as
discussed in Chapter 5.
Chapter 3 presents summaries of important data for Norwegian dams recently com-
pleted or under construction with asphaltic concrete core. The maximum core thick-
ness so far required is 0.9 m (Storglomvatn Dam, 125 m high), and the specified
minimum thickness is 0.5 m. The central core is vertical, except in one case, the
Storvatn Dam to be presented in detail in Chapter 5.
The thin asphaltic concrete core has to follow and adjust to the movements and
deformations imposed by the embankment as a whole. These deformations must be
accommodated by the asphaltic concrete without cracking or significant shear dilation
(volume expansion) which may lead to increased permeability. To reduce the proba-
bility of core cracking due to excessive static and/or dynamic embankment deforma-
tions and distortions, the embankments have all been well compacted.
14
Almost all have so far been rockfill dams resting on firm ground or bedrock. How-
ever, based on acquired experience, that is no longer considered a requirement. For
future situations with embankments placed on top of compressible river deposits,
extra core flexibility and ductility may be provided by designing a richer asphaltic
concrete mix (Chapter 6). Mixes with a bitumen content 2 - 3 % points above the
5-6% which gives optimum density, may still be compacted and controlled by the
procedures described below. Furthermore, one has also started with the use of softer
less viscous bitumen, which increases the crack "self-healing" abiUty and allows
lower operating temperatures during core placement. Thus, through further develop-
ment, one may extend the applicability of the asphaltic concrete core design method
to other site conditions than it so far has been used for.
2.3 Core construction procedure

Details of the core construction procedure and equipment are presented in Chapter 4
and only a very brief overview is given here (Fig. 2.1).
The asphaltic concrete is compacted at a temperature around 160°C depending on

the type of bitumen used, and is given immediate lateral support from the adjacent
zones in the embankment. Placement of the core wall and filter/transition zones
proceed simultaneously, with equal layer thickness, usually limited to 0.2 m, and
compaction is achieved by vibratory rollers which follow the placing unit. The
15
rollers operate in a coordinated manner, side by side, to avoid lateral displacement
of the hot asphaltic concrete.
The asphaltic concrete is produced in accordance with specifications for grain size
distribution of the concrete aggregates, filler and bitumen content in the mix, any
admixtures, and temperature constraints at the various stages of the process (Chap-
ters 6 and 7).
16
Chapter 3
Norwegian Dams with Asphaltic Concrete Core
Table 3.1 below gives key figures for seven Norwegian rockfill dams with com-
pacted, asphaltic concrete core built since 1978. In addition, two more are under
construction. The Storglomvatn Dam, 125 m high, will be the highest so far built
with an asphaltic concrete core.
Table 3.1 Norwegian rockfill dams with asphaltic concrete core
Height Core Vertical Volume

above thick- Core projec- of as- Con- Main
Name lowest ness incli- tion area phaltic struc- contractor/ Main
core foun- (m) nation of core con- tion Asphalt dam owner
dation Top/ (v:h) (m^) crete period contractor
(m) bottom (m')
Vestredalstjem 32 0.5 1:0 6000 3100 1978-80 Selmer'VStrabag Oslo Energy
Katlavatn 35 0.5 1:0 4600 2300 1979-81 Selmer/Strabag Oslo Energy
Langavatn 22 0.5 1:0 3800 1900 1979-81 Selmer/Strabag Oslo Energy
Norwegian
Storvatn 90 0.5/ 1:0.2 76000 49000 1981-87 Statkraft/ Energy
0.8 Veidekke^' Corporation
Veidekke/ Nyset-
Riskallvatn 45 0.5 1:0 14600 8000 1983-86 Korsbrekke Steggje
and Lorck Kraft A/S
Veidekke/ Nyset-
Berdalsvatn 62 0.5 1:0 13000 6800 1986-88 Korsbrekke Steggje
and Lorck Kraft A/S
Statkraft/ Norwegian
Styggevatn 52 0.5 1:0 30400 15300 1986-90 Korsbrekke Energy
and Lorck Corporation
Storglomvatn Statkraft/ Norwegian

(under 125 0.5/ 1:0 44000 22500 1993- Korsbrekke and Energy
construction) 0.9 Lorck-Veidekke Corporation
Holmvatn Statkraft/ Norwegian

(under 56 0.5 1:0 12000 6200 1993- Korsbrekke and Energy
construction) Lorck-Veidekke Corporation
At the time the company name was Furuholmen

At the time the company name was Hesselberg
In the following some key information about the dams listed in Table 3.1, ranked
according to height, is presented. Table 3.2 gives details about the asphaltic con-
crete core mix used for the different dams, and Table 3.3 presents material proper-
ties and compaction procedures for the various embankment zones referred to on the
2. Asphaltic -
17
cross sections in Figs 3.1 - 3.8. (Note: The thick crown cap protection is a
requirement imposed by the Norwegian civil defense authorities as a safeguard
against acts of war.)
Table 3.2 Asphaltic concrete mix design for the dams listed in Table 3.1
Core
Dam thickness Aggregate Filler Bitumen
Name height (m)
Raki- Total Crushed Con-
(m) Top/ Type Impact ness content from Added tent Type
bottom value index aggregate
Grain size (%) (%) (%) (%)
Natural
Storglomvatn 125 0.5/ gravel 34 1.29 13 max. 6.5 min. 6.5 6.3 B180
0.9 + 50% to to crushed
crushed 45 1.43 limestone
0-18 mm
Crushed 34 1.29 7-8
Storvatn 90 0.5/ gneiss to to 12 4-5 crushed 6.2 B60
0.8 0-16 mm 45 1.43 limestone
Natural
Berdalsvatn 62 0.5 gravel 20 1.29 11 6-8 4-6 6.1 B60
+ 20% to to crushed
0-20 mm
Crushed
Styggevatn 52 O.S granitic 43 1.33 12 5-7 5-7 6.3 B60
gneiss to to crushed
0-16 mm 45 1.43 limestone
Natural
Riskallvatn 45 0.5 gravel 35 1.28 U 1-5 6-10 6.3 B60
+ 20% to to crushed
0-20 mm
Natural 40 1.39 6
Katlavatn 35 0.5 gravel to to 12.5 6.5 crushed 6.3 B65*
Natural 40 1.39 6
Vestredalstjem 32 O.S gravel to to 12.5 6.5 crushed 6.3 B65
Natural 40 1.39 6
Langavatn 26 0.5 gravel to to 12.5 6.5 crushed 6.3 B65
* The top 7 m of core was built by the stone-bitumen method with bitumen type B180 (see Section 2.1)
Remarks: • Chapter 6 gives the principles, procedures and terminology con-

cerning asphaltic concrete mix design and required properties.
• The grain size distribution for the aggregate with filler satisfies the
Fuller design curve (Section 6.2).
18
• Asphaltic concrete with bitumen types B60 and B65 is compacted at
a temperature of 160°- 180°C and with type B180 at 140°- 155°C.
Table 3.3 Description of embankment zones for the dams listed in Table 3.1
Compaction''
Zone Material Layer thickness
(m) Vibratory roller, Number of
min. weight (tons) passes
(1) Asphaltic See Table 3.2 0.2 Trials on site, Until void
concrete approx. 0.25 - 0.50 2' content
core < 3%
(2) FUter/ Natural gravel or crushed 0.2 1.5 3-6"

transition rock, 0-60 mm
(3) Transition Crushed rock, 0-200 mm 0.4 15 -1- water sluicing 4
(4a) Shoulder Quarried rock, 0-400 mm 0.8 15 -1- water sluicing 8

(sheU)
(4b) Shoulder Quarried rock, 0-800 mm 1.6 15 6

(sheU)
(5) Slope Selected, large blocks Individually placed - -

protection > 0.5 m' by backhoe
(6) Crown Selected, large blocks Individually placed - -

cap > 1.0 m' by backhoe
(7) Toe drain Selected, large blocks Dumped in lifts - -

> 0.5 m' up to 4 m
The specifications under compaction of fill materials are for the Storglomvatn Dam (Fig. 3.1).
For the other dams (Figs 3.2 - 3.8) the requirements may have been specified somewhat
differently.
In general, the optimum vibratioty roller dq)ends on properties of asphaltic concrete mix and
core width.
Number of passes has to be adjusted on site as it depends on properties of filter material.
19
Fig. 3.1 Site and cross section of Storglomvatn Dam
Maximum height: 125 m Crest length: 825 m Total embankment volume: 5.3 mill, m''
The dam is currently under construction (1993). The alluvial overburden to bedrock
(maximum depth 20 m) has been excavated. The rock foundation grouting will take
place partly from the surface and partly from a mnnel 20 m deep under the right half
of the dam which rests on a complex karstic rock formation.
Storglomvatn is located at the latimde of the Arctic Circle, where the effective
embankment construction season is from about 1 July - 1 November. The site is
inaccessible due to snow during the rest of the year.
The detailed work specifications for the core (zone 1) and filter/transition (zone 2)
are presented in Section 7.2.
20
^
Fig. 3.2 Storvatn Dam
Maximum height: 90 m Crest length: 1472 m Total volume: 9.5 mill, m^
Chapter 5 presents details about design, construction and performance of the Storvatn
Dam.
Performance
The total seepage registered at maximum reservoir level is only 10 l/s. However,
part of this comes from underseepage and from the abutments, so the leakage
through the core is even smaller.
The measured maximum settlement at the top of the core is 165 mm, or 0.18% of
the dam height, 5 years after end of construction. The maximum embankment dis-
placement is registered inside the downstream shell at mid-height and is 580 mm
(520 mm vertically and 206 mm horizontally).
21
Concrete s
Grout curtain
Fig. 3.3 Berdalsvatn Dam
The unusual zoning in Berdalsvatn as compared to Storglomvatn (Fig. 3.1) and

Styggevatn (Fig. 3.4), is because more suitable natural gravel than originally antici-
pated, was found in the borrow area. Therefore zone 2 was expanded with zone 2a,
which reduced the extent of zone 4a and thus the total cost. Core placement and
compaction were achieved by the equipment and procedures described in Chapter 4.
Petformance
The total seepage is very small and less than 2.5 1/s.
Only movements of points on the dam surface and top of core are monitored.
Maximum measured settlement at the top of the core is 70 mm, or 0.1 % of the dam
height, 3 years after end of construction.
22
Grout curtain •—''~ g ^'^^'^
Fig. 3.4 Styggevatn Dam
Maximum height: 52 m Crest length: 880 m Total volume: 2.5 mill, m-'
Core placement and compaction were achieved by the equipment and procedures
described in Chapter 4.
Performance
The total seepage registered at maximum reservoir level is 20 1/s. A significant part
of this does not come from the reservoir through the core but from underseepage and
from the abutments.
Only movements of points on the dam surface and top of core are monitored. The
maximum settlement at top of the core is 35 mm one year after end of construction.
The maximum displacements are 67 mm vertically and 68 mm horizontally at about
midheight of the downstream slope.
23
Fig. 3.5 Riskallvatn Dam
The unusual zoning in Riskallvatn Dam is because more suitable natural gravel than
originally anticipated, was found in the borrow area. Zone 2 was therefore ex-
panded with zone 2a, which reduced the width of zone 4a and thus the total cost.
Core placement and compaction were achieved by the equipment and procedures
described in Chapter 4.
Performance
The total seepage increased rapidly when the filling of the reservoir started in August
1986. When reaching elevation 971 m, the leakage was 106 1/s. The seepage,
which primarily took place beneath the foundation sill, is now, 6 years after first
reservoir filling, 20 1/s at the highest regulated water level (980.3 m). No remedial
grouting has been carried out. The significant reduction is due to a gradual clogging
and sealing of cracks in the rock foundation.
maximum vertical settlement recorded at the top of the core is 45 mm 6 years after
end of construction. This is 0.1 % of the dam height.
24
Fig. 3.6 Katlavatn Dam
The width of the core sill (plinth) is 1.5 m, and upstream along the sill there is a
3 m wide strip of moraine to reduce any potential leakage at the core base.
During the 1980-season the construction of the compacted asphaltic core was very
much behind schedule. It was therefore decided, as no extra placing machine was
available, to construct the top 7 m of the core by the stone-bitumen method described
in Section 2.1. Crushed rock (uniformly graded) and bitumen B180, which has con-
siderably lower viscosity than B65, were used for this purpose.
Petformance
The total seepage registered is stable at 0.4 1/s at maximum reservoir level.
maximum vertical settlement at top of core, 12 years after embankment construction,
is 35 mm, i.e. 0.1 % of the dam height.
25
2r*^**«-=^
.-•«•.. «ü. J 'î^mïîrr' -aR'StiSi
Grout curtain
Fig. 3.7 Vestredalstjem Dam
Performance
Only movements of points on the dam surface and top of core are measured. The
vertical settlement of the top of the core, 12 years after embankment construction,
is 44 mm, i.e. 0.14% of the dam height,
26
Fig. 3.8 Langavatn Dam
Maximum height: 26 m Crest length: 290 m Total volume: 0.3 mill, m-^
Performance
Only movements of points on the dam surface and top of core are measured. The
vertical settlement of the top of the core, 12 years after embankment construction,
is less than 0.1% of the dam height.
27
Chapter 4
Norwegian Construction Equipment and Practice
After the three first dams were completed (Table 3.1), new and improved equipment
for placing the asphaltic concrete core was designed and built for the construction
of the Storvatn Dam in 1981. Since then, further improvements have taken place to
increase the mobility of the paver, reduce extent of hand placement required, and to
simplify transportation and loading of asphaltic concrete into the paver.
The present Norwegian equipment, shown in Figs 4.1 and 4.3 has been used on
three dams in Norway (1987 - 1991) and one in Jersey, U.K. (1990 - 1991). In the
Norwegian mountains, the paving season is short due to severe winters with much
snow. However, the paving equipment has proved itself and shown that core
building can be performed within strict specifications even under very wet and cold
conditions.
Fig. 4.1 The Norwegian asphaltic concrete paver at work on Styggevatn Dam
4.1 Asphaltic concrete plant

A reliable batch plant with a capacity of 50 - 60 tons an hour is normally sufficient
(Fig. 4.2). The plant should have a minimum of 4 hot aggregate storage bins, and
a data printout of all weights per batch is recommended (Section 7.2).
29
As daily output is moderate and production often somewhat discontinuous, special
care is put on temperature controls. An airbag filter is used to regain all the aggre-
gate fines from the crushing process. With the high content of filler required in the
mix (approximately 12% smaller than 0.075 mm), added filler in the form of Port-
land cement or crushed limestone is normally specified to give a mix good working
characteristics. Two storage silos are therefore required, one with the added
material, and the filler is composed of a prescribed mixture which depends on the
acidity of the crushed aggregate fines.
Fig. 4.2 The batch plant erected close to the downstream toe of
Riskallvatn Dam
4.2 Core paving equipment

The paving equipment shown in principle on Fig. 4.3 places asphaltic concrete and
filter simultaneously in 20 cm horizontal layers (after compaction). The machine is
a hydraulically driven crawler paver, and the widths of the core and filter screeds
are adjusted according to the design specifications. The level of the filter screed is
automatically controlled by a rotating laser which ensures a horizontal base for the
next layer.
The precise center line is marked for each layer and fixed by a thin metal string.
A video camera mounted in front of the machine and a television monitor inside the
cab enable the operator to steer the machine with precision following the course of
the string.
30
Laser controlled cleaner
screed
Fig. 4.3 Working principle for core paver
In front, the machine is equipped with a gas fired, infrared heater and a heavy duty
vacuum cleaner which removes dust and moisture. The heater dries and heats the
surface before the next layer is placed. No tack coat is applied between the asphaltic
concrete layers as core sampling has proved that the joint is tight and hardly
detectable.
Asphaltic concrete and filter are compacted by three vibrating rollers as shown in
Fig. 4.4. The center roller should be somewhat wider than the asphaltic core. As
31
the mix is soft, the roller must not be too heavy, but the compaction energy must be
sufficient to give an in-situ void content which satisfies the design requirements
(Chapter 6).
«iSKfo.- - •• .... - -r.^.,. :••• • .<^^,r*v<a,
Fig. 4.4 Simultaneous compaction of core and fdters
Fig. 4.5 Loading of aspaltic concrete and filter material into paver
32
Compaction of the filter is achieved by two 1.5 - 2.5 tons vibrating rollers working
in parallel (see Table 3.3). The sequence and amount of compaction have to be
adjusted on site and depends on the asphaltic concrete mix and the filter material
being used.
Transportation and loading of asphalt has been simplified after introducing wheel-
loaders with specially designed insulated buckets to maintain the strict temperature
control. The asphalt plant must be erected close to the dam if transport with wheel-
loaders alone shall be sufficient. Fast and reliable supply of asphaltic concrete and
filter material is essential. The filter material is transported in heavy duty trucks and
loaded into the machine by an excavator. A storage bin pulled by the same
excavator has in most places proved advantageous (Fig. 4.5).
4.3 Placing and compaction procedm-es

The concrete base (foundation sill) for the core should be planned and designed in
order to minimize required hand placement of asphaltic concrete. Hand placement
inside formwork (shutters) with the filter outside, is time-consuming and expensive,
but usually necessary, to establish a horizontal base for the core paver (Fig. 4.6).
Fig. 4.6 Hand placement of asphaltic concrete
The accumulation of water in the low points of the foundation is a problem, and the
use of water pumps is normally required. As the concrete surface has to be dry and
3. Asphaltic -
33
clean before the layer of asphalt mastic can be placed, the concrete base (sill) should
be made with a slight cross elevation. When the concrete sill is within a deep ditch,
this has to be wide enough to accommodate the machinery.
The concrete surface should be rough but even. Any spoils from injection grouting
must be removed. In order to secure good adhesion between the concrete and the
asphalt mastic, the concrete is either sand-blown or washed with hydrochloric acid.
Stearin acid is added to the asphalt mastic in order to secure good adhesion
(Fig. 4.7).
Fig. 4.7 Placement of asphalt mastic on the foundation sill
The asphalt mastic surface must be cleaned and heated before asphaltic concrete is
placed on top.
Hand placed asphaltic concrete and filter, levelling, removing of formwork and com-
paction have all to be done in quick succession in order to meet the specifications
for temperature and maximum allowable air void content (porosity).
Having established a horizontal core base (minimum 30 m long), one may commence
using the paving machinery. However, some hand work will always be required at
each abutment. Progress should be continuously adjusted in accordance with the
plant and transport facilities, normally 1 to 3 meters per minute. If stops exceed 10
to 15 minutes, proper construction joints must be made before proceeding.
34
Filter is placed with an extra height above the asphaltic concrete level corresponding
to the difference in compressibility. As filter and asphalt mix vary from project to
project, compaction routines are established for each new project to achieve the
specified in-situ density.
The asphaltic concrete surface will curve somewhat (convex) after layer compaction,
and fine cracks will occur in the middle. These fine cracks are of no concern as
they will disappear when the next layer is placed.
The cross section of the core wall has to be controlled periodically to check for
lateral deformations due to uneven compaction. This is achieved by excavating
down on each side of a short section of the core.
As the dam construction progresses, the various zones are raised simultaneously.
Where rain or snow or seasonal stoppages can cause delays, it is advisable that the
core and filter level at all times in any cross section is higher than that of the
adjacent fill upstream and downstream.
Transport across the asphalt core is normally a necessity for construction purposes.
Light steel bridges, which easily can be removed, are required for this purpose, and
no vehicle is permitted to cross the core except over a bridge (Fig. 4.8).
Fig. 4.8 Light steel bridge across the core
35
4.4 Quality assurance and control
There are rigorous specifications for the construction of watertight asphaltic concrete
cores. Quality assurance and control (QA/QC) are required to comply with these
specifications. An example of contract specifications is presented in Chapter 7, and
only a few special points are mentioned here.
Fully automatic batch plants with computer printout for each batch are used on
Norwegian dams. Statistics indicate that the plant computer controls the bitumen
content and aggregate weights more accurately than the control laboratory tests can
measure. Table 4.1 shows an example from Storvatn Dam (Chapter 5) of the weekly
recorded standard deviation of mix parameters in per cent.
The computer alerts the operator if the proportion of any material deviates from the
preset limits. Scales and screens in the asphah plant must be checked regularly as
ertors in these are not detected by the computer. Mechanical properties of the aggre-
gates including grain size distribution must be determined daily during production,
and settings for the crusher openings and sieves must be adjusted to compensate for
natural wear.
Removal of unacceptable asphaltic concrete placed in the core is expensive, time-

consuming and difficult, and the number one rule is therefore never to gamble on the
quality of any asphaltic concrete delivered for placement (Section 7.2).
Drilling in order to obtain control specimens from the core, can only be performed
when the asphalt has cooled down. This normally takes several days, and core
drilling can accordingly not be performed as a daily control. New control methods
measuring the density (void content) by means of non-destructive, isotope methods
have proved promising. However, these methods require further development to im-
prove accuracy and reliability and do not yet eliminate the need for periodic core
drilling.
Table 4.1 Weekly standard deviation of mix parameters from design values at
Storvatn Dam (given in per cent)
Bitumen Filler Content of Content of Content of
content content < 2 mm < 4 mm < 8 mm
0.0587 0.0089 0.184 0.213 0.140
0.0622 0.103 0.233 0,270 0.146
0.0380 0.133 0.195 0.286 0.201
0.0611 0.122 0.409 0.576 0.262
0.0544 0.095 0.300 0.254 0.151
0.0500 0.086 0.220 0.141 0.123
0.0843 0.102 0.392 0.263 9.177
0.0585 0.068 0.220 0,221 0.226
0.0692 0,122 0.454 0.619 0.266 !
0.0597 0.165 0.409 0.326 0.203
0.0717 0.132 0.433 0.492 0.284
36
Chapter 5
Case Study - The Storvatn Dam
The Storvatn Dam and 3 other large and 9 small dams of various types form the
Blasjo Reservoir which is part of the Ulla-Forre scheme. The location is in South
West Norway, about 60 km east of the city of Stavanger. Two power stations, two
pumped power stations and one pump station account for a net production of ap-
proximately 4500 GWh in an average year. The Blasj0 Reservoir, with a capacity
of 3.1 x 10' m^, is situated on a mountain plateau, and the maximum storage level
is 1055.0 m a.s.l. (see Fig. 1.1). The Storvatn Dam, which is presented below, was
completed in 1987.
5.1 Dam design

At the early planning stage in the late 1960's, Storvatn Dam, as well as the other
large embankment dams around the Blasjo Reservoir, were designed as rockfill dams
with central core of moraine. The design volume of Storvatn Dam was then 10 x
10^ m-' with a maximum height of 90 m. Rockfill could be quarried at the site, but
the hauling distance of morainic material and filter material was 42 km and 28 km,
respectively, which was greater than for the other dams in the scheme. The large
cost of transportation including extra cost to build mountain roads to allow the heavy
transport, called for an alternative design. This request was also supported by the
fact that the total volume of borrow material was limited. Therefore, if Storvatn
could leave the moraine to be used in the other dams, their thin cores could be
widened and made safer.
Four alternative impervious elements were examined:
• Upstream facing of Portland cement concrete or asphaltic concrete

• Central core of asphaltic concrete
• Central core of crushed rock with grain size distribution similar to that of
moraine
To decide among these alternatives the following points of consideration were

evaluated:
• Construction cost
• Value of water stored during construction
• Sensitivity to severe weather conditions during construction
• Performance of previously completed dams
It would take three years of average precipitation to fill the reservoir, and the eco-
nomic value of water which could be stored during construction was significant. A
rockfill dam with an upstream facing cannot store water during construction to the
same degree as a dam with a central core, and an estimate of total cost and benefit
37
favoured the latter type. The final decision was therefore whether the central core
should consist of asphaltic concrete or crushed rock.
The rock at the site consists mainly of granitic gneiss, and test results showed that
quarried rock could be crushed down to a grain size distribution similar to moraine.
The crushed rock was sufficiently impervious and behaved in laboratory testing very
much like a coarse grained moraine. It was therefore considered suitable as core
material.
Cost estimates showed that at equal cost the maximum gradient through the core of
crushed rock would be 3 compared to the maximum gradient through the asphaltic
core of about 100. However, the crushing of 0.75 x 10^ m^ of rock down to the
grain size of a moraine has no precedence in Norway, whereas the production of
50,000 m-' of asphaltic concrete over several years could be handled with well-known
equipment. Furthermore, the construction of the core of asphaltic concrete would
be much less sensitive to bad weather conditions than the core of crushed rock.
In the late 1970's the choice was made. The Storvatn Dam should be a rockfill dam
with a central core of asphaltic concrete. When that overall decision was made, the
further design involved location of the dam axis, foundation preparation, cross sec-
tion geometry and zoning of the dam embankment.
Location and alignment of the dam axis
Generally the dam axis should be located in such a way that the volume of the dam
is a minimum, and if no significant additional volume is required, the dam axis
should be curved convex to the reservoir.
At the site of Storvatn the axis giving the minimum volume is partly straight, partly
curved concave and partly convex to the reservoir (see Figs 5,1 and 5.2). A straight
axis all across the namral lake gave a maximum height of dam approximately 10 m
higher and the corresponding volume about 10* m-^ larger. For a dam everywhere
curved convex to the reservoir the difference would be even larger. Avoiding the
local concave curvamre of the dam required an extra cost of approximately 10%.
The question was therefore how large negative effects a concave curvature would
have on the dam behaviour. It is well known that an internal core in a rockfill dam
usually displaces a little upstream during the early stages of filling, but is
subsequently pushed downstream as unpounding proceeds. This displacement would
create extensional strains in the core of concave curvature and could, depending on
the extent of straining, lead to transverse cracks. Finite element analyses showed,
however, that the extensional strains to be expected would be very small and
acceptable. They would be smaller than those predicted at the steep right abutment.
The alignment of the dam as shown on Fig. 5.2 was therefore decided upon in spite
of the undesirable curvamre over a portion of the embankment.
38
Fig. 5.1 Photo of Storvatn Dam showing the unusual alignment
Foundation
The asphaltic core should be founded on a concrete structure in a rock trench, and
a grout curtain should be constructed underneath. A main question was, however,
whether this concrete strucmre could be a simple concrete sill or should be a com-
plete gallery.
The extra cost of erecting a gallery was estimated to approximately 10% of the total
cost of the dam. Furthermore, erecting a gallery would possibly extend the period
of construction by one year. Would the advantages of a gallery be worth the extra
construction and time costs?
A concrete gallery may serve as a grouting gallery as well as an inspection gallery.

However, the advantage of carrying out the primary construction grouting from a
gallery was looked upon as minor or nil. The advantage of a grouting gallery there-
fore depended on the potential need for supplementary grouting during the lifetime
of the dam. Based on the results of ten exploratory diamond drilled holes to depths
greater than 50 m, the likelihood that the planned grout curtain would need future
repair was judged to be very small. In any case, a potential future increase in per-
meability of the rock foundation, which in this formation would have to be moderate,
was evaluated to be of relatively little economic significance. If essential, leakage
at a later stage could be reduced by grouting from adits (tunnels) driven under the
dam, at a cost corresponding to that of a gallery.
39
[)/_Valve
chambre
Diversion tunnel
Top of dam m.a-s.

1060 T
"~"~^---_ /^ J040-
1020-
•
Scale Grout turf am - 1000-
Station No.
0 250 600 750 1000 1250 150
1.5 I I ('6^ V 1061,0
® P®
Fig. 5.2 Design of Storvatn Dam

A. Plan and cross-valley profile
B. Principal cross section
C. Core base and foundation sill
40
The grouting work subsequently carried out involved 2080 boreholes, three rows,
c/c 1.5 m, to a maximum depth of 75 m, making up 32,140 m and a grout take of
180 tonnes. The cost of this work corresponds to approximately 15% of the cost
difference between a concrete gallery and a simple concrete sill. Therefore, when
the foundation consists of good rock, as is the case for the Storvatn Dam, the cost
of a grouting gallery seems to be an unreasonably high insurance premium.
On the advice of the consulting engineer, the owner decided to omit the concrete
gallery and let the asphaltic core rest on a concrete sill. This sill was to be cast in
a rock trench, reinforced and anchored. The width of the sill varies between 4 and
5 m. The minimum depth of the trench was set at 0.5 m, the minimum thickness
of the sill to 0.75 m, and the sill should not anywhere protrude more than 1.5 m
above the adjacent rock surface. Some chemical grouting was used to seal cracks
in the concrete sill after construction. (It may be noted that for the Storglomvatn
Dam currently under construction on a karstic foundation, a grouting tunnel at
approximately 20 m depth is included as described in Chapter 3).
Omitting the concrete gallery at Storvatn Dam, made it necessary to collect and
measure the seepage downstream of the core where it was recorded within eight
separate segments along the dam.
Cross section and specified compaction
The cross section of the dam was designed and built with the aim to minimize the
embankment displacements and deformations as much as possible within practical
and economical constraints. Final zoning, material and compaction specifications are
presented in Fig. 5.2 and Table 3.3.
The thin core wall is inclined, producing a favourable transfer of the water load to
the downstream rockfill and foundation. Even the top of the core wall is situated up-
stream of the centre line of the dam, leaving a large proportion of the rock fill as a
support for the water load.
The thickness of the core wall decreases in steps of 0.1 m from 0.8 m at the base
to 0.5 m at the top. The core rests on a slab of asphaltic concrete 0.4 m thick and
1.5 m wide, placed on top of the concrete sill. The interface between the asphaltic
slab and the concrete sill was cleaned by sand blasting, primed and coated with
asphaltic mastic with a special additive to enhance interface bonding.
The asphaltic concrete in the core wall was specified to be placed in layers of 0.2 m
thickness. Each layer is displaced 50 mm downstream in relation to the foregoing
layer to obtain the prescribed inclination of the core. The thickness of the wall is
defined as the width of the interface between successive layers. Adjacent to the
core, a zone 1.5 m wide, consisting of crushed rock 0 - 60 mm, is placed in layers
of 0.2 m and compacted by vibratory rollers simultaneously with the asphaltic con-
crete.
41
Between zone 2 and the supporting fill of blasted rock (granitic gneiss) is placed a
transition zone (zone 3) of processed rock 0 - 2(X) mm. This zone, 4 m wide, is
placed in layers of 0.4 m and compacted by vibratory rollers. Zone 4a is placed in
layers of 0.8 m, sluiced and compacted by vibration, whereas the rock in zone 4b
is placed in layers of 1.6 m and compacted by vibration without sluicing. The slope
protection upstream and downstream consists of blocks weighing approximately 1.5
tonnes each, individually placed by backhoe.
The design analyses included use of the finite element method for computing
embankment displacements and deformations to assure that the strains imposed on
the core were acceptable (Section 5.3). Furthermore, special earthquake analyses
were performed as described in Section 5.4.
Mix design of asphaltic concrete
The asphaltic concrete mix design specified:
• Quality and grain size distribution of aggregates

• Quality and content of bitumen
• Temperature at which the aggregates and bitumen should be mixed and
compacted
• Upper limit of allowable air void content (porosity) of compacted asphaltic
concrete in core
Based on laboratory prepared specimens with aggregates from the borrow pit, the
owner specified the preliminary mix design in the tender documents. In these docu-
ments it was required that the contractor carry out additional testing on asphaltic con-
crete produced by his plant at the site. The contractor had the right and obligation
to propose suitable adjustments to the specified mix before starting the construction
of the asphaltic concrete core (see work specifications presented in Section 7.2).
5.2 Construction and control of the asphaltic concrete core

Construction
Up to-date Norwegian construction equipment and procedures are presented in

Chapter 4.
The construction season at Storvatn was limited to between mid-May and mid-
October. Snowdrifts up to 15 m prevented the access road to the dam from being
opened before the first part of May. In the summer, heavy rain was prevailing, and
the annual precipitation in the area is between 2500 mm and 3000 mm.
The plant for the production of the asphaltic concrete for the core was erected down-
stream the eastern part of the dam, giving transport distances in the range 1-3 km.
The zone 2 material was produced in a cmshing plant located on the same site as the
42
asphalt plant, and the aggregates for the asphaltic concrete were produced by the
same plant.
The core placing equipment was designed and constructed especially for this job,
taking advantage of the experience from the three first Norwegian dams built with
compacted asphaltic concrete core (Table 3.1). Some special considerations at
Storvatn were:
• construction should take place unhampered by wind and rain;

• very small tolerances were allowed regarding deviation from the centre line,
as the dam core was not vertical but sloping 5:1;
• there was a requirement that the surface of the previous layer could be
inspected immediately before the next layer was to be placed.
The construction took place with one asphaltic concrete placing machine during the
first two construction seasons, but as the crest length increased, a second unit was
brought into use as well. The actual production rate had to be adapted to the placing
of the embankment and varied between 1 and 3 layers per day. The placing equip-
ment was fitted with a two-stage vibrating screed for initial compaction of the asphal-
tic concrete, while the zone 2 material was initially compacted by a static roller and
vibratory plate, connected to the back part of the machine. Both zones were then
compacted by vibratory rollers to the specified density. (This equipment developed
in 1981 for Storvatn Dam was not quite as advanced and convenient as today's
version presented in Chapter 4).
Quality assurance and control (QA/QC)
Quality control was exercised at every stage of the production, from monitoring the
mixing plant and placing operations to sampling of raw materials as well as the
finished core. To ensure high quality in the mixing process, a computer controlled
asphalt plant was installed. Reports from the computer were displayed on the
operator's screen and compared with the specified grain size distribution (Fig. 5.3).
For further details concerning QA/QC, reference is given to Chapters 4 and 7, and
only a few points are mentioned here.
The properties of the asphaltic concrete mix were determined daily. The results had
to be presented quickly in order to stop the work if some irregularity should occur.
For every fifth layer and every 200 m section of the dam, vertical cores of 0.1 m
diameter and 0.4 m length were taken. Additional cores were drilled on spots where
visual control gave reason for concern. All cores were subject to tests for air void
content which was required to be less than 3 %.
The core length of approximately 0.4 m made it possible to go through two layers.
All inspected layers proved to be properly bonded to each other with joints as tight
as the layer itself.
43
The density (porosity) was also determined by means of a nuclear frequency counter.
This equipment has the great advantage that it provides an estimate of the void
volume within ten minutes after core compaction. However, on Storvatn Dam these
results proved to be unreliable, and further development of the technique would have
been required to make it useful in the quality control programme. (Entirely satisfac-
tory equipment and techniques still do not exist today, 1993.)
100 7
//
90 //
' t ',
80 \
70 Des inn miY
CO \
60 i 1 \
^/
Tolerances v,^ '\
t'^
50 /
O \ N
cc 40
*-*
y/
30 K-
^ -^.^-^ --* ^
É 20
C/3
CD
>> "
10
<
Q. ^ i. i- i . V-
1
0,075 0,25 0.5 1,0 2.0 4.0 8,0 16.0 32.0 64.0
PARTICLE SIZE (mm)
Fig. 5.3 Specified grain size distribution for aggregates

in asphaltic concrete (Fuller's curve)
5.3 Predicted and observed dam performance

Field instrumentation programme
The extensive field instrumentation for Storvatn Dam, concentrated in three cross
sections at stations 610, 730 and 940 (Fig. 5.2), included 12 inclined, vertical or
horizontal inclinometer casings to measure deformations in the embankment and 28
extensometers for strain measurements in the asphaltic concrete core. Additionally,
284 survey monuments were located at regular intervals and at various levels along
the embankment to measure surface displacements.
The leakage water is collected between the core foundation and walls erected 10-
20 m further downstream. Within this area the leakage is registered for eight
separate segments along the dam to localize any source of leakage. The registration
is automatic and remotely recorded.
Leakage measurements
The measured total leakage is very small considering the height and length of dam.
The highest total leakage is recorded at 10.2 1/s. However, some of the registered
leakage water does not originate from the reservoir. A cross valley groundwater
44
flow was observed within section B (see Table 5.1 below) before raising the water
level, and the measurements show that the total leakage decreased by up to 2 1/s
during the cold winter months despite the constant reservoir level. Several months
with temperamre well below freezing will most certainly reduce a possible ground
water flow and therefore explains the recorded reduction in leakage.
Table 5.1 Registered leakage at Storvatn Dam
Registered leakage, 1/s

Storage
Segment
Date level,
(Distance in m along the dam) Total
m.a.s.l.
A B C
(25-1450) ]
(25-350) (350-1155) (1155-1450)
850425 1004.7 6.7 0.2 6.9
860406 1025.2 0.2 8.0 1.5 9.7
870412 1041.1 0.1 7.8 2.2 10.1
871115 1050.5 0.2 8.0 2.0 10.2
881021 1052.2 0.1 8.0 1.9 10.0
890815 1055.3 0.1 7.0 1.9 9,0
901001 1054.6 0.1 6.6 0.9 7,6
911008 1052.2 0.1 6.2 0.8 7.1
920722 1052.6 0.3 6.8 0.4 7.5
The very small leakage recorded at Storvatn Dam is consistent with corresponding
leakage measurements at for instance Finstertal Dam (Austria) and Megget Dam
(Scotland), when the vertical projection area of the corresponding cores are con-
sidered. The conclusion is that a properly designed and constructed asphaltic con-
crete core is virtually impervious.
Prediction of embankment deformations
Both linear and non-linear two-dimensional finite element analyses were performed,
applying the sequendal loading method described by Clough and Woodward (1967).
The procedure used for approximating the material stress-strain behaviour is by suc-
cessive load increments, within which the material behaviour is assumed to be linear.
After each increment the deformation properties are re-evaluated in accordance with
the stresses in the element. Three-dimensional, linear analyses were also performed
to evaluate the accuracy of the two-dimensional idealizations.
The stress-strain properties of the rockfill were determined both through laboratory
tests and field plate loading tests. The laboratory test programme consisted of four-
teen triaxial tests and six oedometer tests. Five of the triaxial tests were carried
out in NGI's large vacuum triaxial cell with specimen diameter 625 mm and height
45
1250 mm (Fig. 5.4). Conventional triaxial equipment with specimen diameter
102 mm and height 200 mm was used for the remaining nine triaxial tests. The six
oedometer tests were performed in a fixed ring oedometer with specimen diameter
500 mm and height 250 mm.
Fig. 5.4 NGI's large vacuum triaxial test
The derivation of material parameters for use in the finite element analyses was
carried out in two stages. In the first stage, the results of the laboratory tests were
used directly in the analyses, and the calculated movements were compared with
measurements taken during the early construction stages. Based on such compari-
sons, a final set of material parameters was selected for the subsequent analyses of
the completion of the embankment and the raising of the water to full reservoir level.
The magnitude and distribution of the vertical and horizontal displacements predicted
by the finite element analyses, are shown in Fig. 5.5 for the maximum cross section
(station 940 in Fig. 5.2). No attempts were made to use the finite element model
to predict the time-dependent creep deformations after end of construction and reser-
voir filling, and empirical relationships from earlier dams were applied for this
purpose (Kjaernsli et al., 1992).
Deformation measurements
The first set of complete deformation measurements was taken in October 1986 when
the embankment was virtually completed (2 m from crest), and the water level was
17 m below full reservoir level. The registered displacements at that stage are
shown in Fig. 5.6.
46
Fig. 5.5 Computed vertical and horizontal displacements in mm for the maxi-
mum cross section at full reservoir level
V 1061,0 ^ 1059.0 Embankmenf level
R e s e r v o i r w I Oct 86 v 1038.0
Scales
0 10 20 30 40 50m 0 02 04 06 08 10m
' ' ' Geometry ' ' ' ' ' —' Displacement
Fig. 5.6 Recorded displacements for the maximum cross section in

October 1986
47
Due to the heavy compaction and good rockfill materials, the displacements are
small. In general, they are in fair agreement with those computed by the finite ele-
ment analyses described above. The displacements originally estimated, using di-
rectly the deformation parameters from the laboratory tests, were somewhat larger
as the in-situ material behaviour was stiffer than the laboratory tests indicated. The
displacements are of similar magnimde to those measured at Finstertal Dam in
Austria, an asphaltic sloping core dam 100 m high (Pircher and Schwab, 1988).
Further comparisons between computed and measured displacements are presented
in the article by Adikari et al. (1988).
The maximum core displacements, which took place at about midheight, were
0.18 m vertically and 0.12 m horizontally in Oct. 1986. The maximum vertical
settlement in the embankment at that time was 0.35 m, at a point located about mid-
height 40 m downstream of the dam axis. The maximum horizontal displacement
was measured near the same location, 10 m further downstream, and was 0.14 m,
Since October 1986 deformation measurements have been taken approximately every
year. However, since 1990 the inclinometer readings inside the embankment have
not been recorded and only the surface movements and settlements of the top of the
core. The reservoir was full for the first time in September 1989. At that time the
maximum vertical and horizontal displacements inside the downstream embankment
were 0.50 m and 0.20 m, respectively, at the same locations as described above.
The recorded settlement vs time for the measuring point at the top of the core since
end of construction is shown in Fig. 5,7. The settlement is primarily caused by
creep, but there are also some contributions from the 17 m increase in reservoir level
between 1986-89 and the load cycles from the slight lowering and raising of the
reservoir level between 1989 and 1992.
•z.
LU
UJ
_i
I-
1-
ai
CO
TIME SINCE END OF CONSTRUCTION (YEARS)
Fig. 5.7 Recorded top-of-core settlement with time after end of embankment
construction (close to maximum cross section at bolt No. XIX)
48
5.4 Predicted seismic response
Design earthquake
The Storvatn Dam is located in an area of moderate seismic activity, and a study was
conducted to evaluate the integrity of the dam under earthquake loading. Analyses
were also performed for significantly more severe earthquakes (high seismicity) than
can ever be expected at that site. This was done to study the ultimate earthquake
resistance of this type of dam and to estimate the permanent (residual) deformations
which could be induced during severe shaking.
The criteria adopted for the selection of the design earthquake loads were in accord-
ance with the recommendations of the US Committee on Safety Criteria for Dams
(1985). Two levels of earthquake loading were considered:
• Operational safe earthquake (OSE): an earthquake event that is likely to occur

during the economic life of the dam. The dam should withstand the OSE with-
out any significant damage and be fully operational afterwards. The OSE was
defined as ground shaking with a probability of occurrence of 5 x 10'^ per year
(remm period 200 years). The OSE corresponds to earthquake Richter magni-
tudes of 6.5 in the Storvatn area (moderate seismicity), and 7.5 in an area of
high seismicity.
• Maximum credible earthquake (MCE): the maximum earthquake event likely to

occur at the dam site. The dam should survive the MCE without any sudden,
uncontrolled release of the reservoir, but damage to the dam and any appurtenant
structures would be tolerated. The MCE was defined as ground shaking with a
probability of occurrence of 10"'' per year (remrn period 10 000 years). The
MCE corresponds to earthquake magnitudes of 7.5 in the Storvatn area, and 8.25
in an area of high seismicity.
Pseudo-static stability analysis
In a conventional pseudo-static, limiting equilibrium, earthquake stability analysis,

a horizontal earthquake force is applied to the sliding body in addition to the static
forces. The additional horizontal force is proportional to the total mass of the sliding
body, and the factor of proportionality is denoted "earthquake coefficient". This
type of analysis is applicable only for dams constructed of materials that do not
experience a significant reduction in strength during cyclic loading. The dense rock-
fill, which makes up the bulk of Storvatn Dam, and the asphaltic concrete core are
of this type. The permeability of the rockfill and the transition zones is so great that
the excess pore pressures generated during cyclic loading dissipate quickly, and no
significant accumulation of pore pressures takes place during an earthquake,
According to Seed (1979), the acceptable design criterion for a rockfill embankment
dam exposed to earthquakes, is a pseudo-static factor of safety greater than 1.15 for
an earthquake coefficient of 0.1 for a magnitude 6.5 event, and an earthquake coeffi-
cient of 0.15 for a magnitude 8.25 event.
4. Asphaltic -
49
Using the infinite slope method, considering the equilibrium of a shallow mass in the
direction parallel to the slope, one may evaluate the pseudo-static factors of safety
for the submerged upstream and the dry downstream slopes in closed-form. Stability
analyses were also carried out by the circular arc method. The friction angle of the
rockfill was specified as function of effective stress level and was conservatively
taken as 43°- 45° on the upstream slope, and 45°- 47° on the downstream slope.
The results are presented in Fig. 5.8 which shows the variation of the computed
factors of safety as function of the earthquake coefficient. The down-stream slope
satisfies the stability criterion (factor of safety > 1.15) for a magnitude 6.5 earth-
quake (earthquake coefficient = 0.1), and the upstream slope fails to satisfy this
criterion by a very small margin. Should a dam like Storvatn be constructed in an
area of high seismic risk, the gradient of the outer slopes of the dam would have to
be decreased to satisfy the pseudo-static stability criterion. For an earthquake of
magnitude 8.25, the upstream slope would need to be flattened from 1:1.5 to 1:1.85
and the downstream slope from 1:1.4 to 1:1.5.
1.75
LU
U.
<
CO
LL
O
tr
O
H
Ü
<
0.75
EARTHQUAKE COEFFICIENT
Fig. 5.8 Results of pseudo-static stability analysis
Dynamic analysis to compute induced permanent displacements
Additional analyses were performed to study the dynamic response of the dam and
to estimate the permanent deformations which could be induced by a severe earth-
quake (Gazetas and Dakoulas, 1992).
Newmark (1965) suggested as a useful approximation that the potential failure mass
in an embankment can be modelled as a rigid block sliding along a potential slip sur-
50
face. The yield acceleration is defined as the horizontal acceleration required to
initiate sliding. This model does not account for the variations in ground motion
along the potential failure surface caused by the dynamic response of the structure.
Makdisi and Seed (1978) therefore proposed an equivalent linear earthquake response
analysis to evaluate an average, effective base motion for estimating the permanent
block displacements. In the study for Storvatn Dam, the acceleration time histories
for the effective motion along the potential failure surface were obtained from
simulations with the finite element computer program FLUSH (Lysmer et al., 1975).
The Taft earthquake in 1952, which had a magnitude of 7.6 was selected as the input
bedrock motion for the analyses. The horizontal component of that earthquake was
scaled to a peak acceleration of 0.5 g, and the vertical component to a peak
acceleration of 0.32 g. Two sets of analyses were carried out. In the first one, only
the horizontal component of the earthquake motion was applied; in the second, both
the horizontal and the vertical components were applied simultaneously. Figure 5.9
shows the contours of the computed maximum horizontal accelerations for the first
case and Fig. 5.10 the maximum horizontal and vertical accelerations at selected
points for the second. Contours of the computed maximum cyclic shear strains are
also shown in Fig. 5.10.
-1 1 1 L — I 1 I 1 I I i 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 I I ^
-100 m -50 m (J 50 m 100 m
Fig. 5.9 Computed maximum horizontal accelerations caused by horizontal

base motion
Valstad et al. (1991) provide details of the analyses and discuss the case where the
permanent shear displacements due to severe shaking of the dam, are so great that
the thin core may be sheared off in the top portion. In their computations they
conservatively assume that the permanent shear displacements are all concentrated
along a single shear surface through the core. In reality the shear distortion may be
distributed vertically over a shear zone and thus be less likely to open a gap between
the top and lower part of the impervious core.
51
Fig. 5.10 Computed maximum accelerations and cyclic shear strains caused by
combined horizontal and vertical base motions
Summary of seismic response analysis
The analyses demonstrate that the Storvatn Dam has an ample margin of safety for
earthquakes in the region. The design would enable the dam to function adequately
even in an area of high seismicity if the inclination of the outer slopes were
decreased from 1:1.5 to 1:1.85 upstream and from 1:1.4 to 1:1.5 downstream. The
same core assembly (core and filter/transition zones) could be used.
During an extreme earthquake, the induced permanent shear displacements for an

embankment dam, may become so large that a narrow core is sheared off and a gap
opens. Then it will be the depth of the gap beneath the water level and the permea-
bility of the filter/transition zones that will govern the magnimde of the leakage rate
until the reservoir is lowered. For such an eventuality it would be advisable to have
a relatively fine-grained material next to the asphaltic core. In any case, it is essen-
tial that the downstream shell and toe is designed with adequate drainage capacity
to handle accidental leakage and prevent dam failure even if the temporary water loss
is dramatic (Kjaernsli et al., 1992).
The main reasons for the favourable seismic behaviour of a rockfill dam with an
asphaltic concrete core are as follows:
• The dam is built with core and embankment materials that do not experience any
significant reduction in strength during cyclic loading. The permeability of the
dense rockfill which makes up the bulk of the dam is so great that the excess
pore pressures generated during cyclic loading dissipate quickly, and no signi-
ficant accumulation of pore pressures takes place during the earthquake.
52
• The dam can tolerate large permanent shear deformations without experiencing
an uncontrolled release of the reservoir water. This type of behaviour is likely
to prevent failure even in the event of an extreme earthquake.
Acknowledgment
The information presented in this Chapter is primarily extracted from the articles by
Amevik et al. (1988), Adikari et al. (1988), Valstad et al. (1991) and recent field
performance observation reports (see list of references in the back). Most of the
work behind these articles has been sponsored by STATKRAFT (The Norwegian
Energy Corporation), and their support and permission to publish the data are grate-
fully acknowledged.
53
Chapter 6
Design - Principles and Requirements
ICOLD Bulletin 84 (1992) presents recommendations related to the use of bituminous
cores in embankment dams. This bulletin supplements Bulletin 42 (1982) with
experience gained through recent developments in construction methods and field
performance monitoring for dams with asphaltic concrete core.
A summary of requirements to design analyses, materials and material testing is pre-

sented below with particular emphasis on results from Norwegian research and field
practice. The requirements to construction equipment and procedures and the ac-
companying work specifications and quality assurance are presented in Chapters 4
and 7.
6.1 Design analyses

The thin asphaltic concrete core has to adjust to the deformations in the embankment
and to differential displacements in the dam foundation (Fig. 6.1). Displacements
accumulate during embankment construction, filling of reservoir, time-dependent
consolidation and creep, fluctuations in reservoir level and any earthquake shaking
or fault movements. The essential function of the core is to remain impervious
without any significant increase in permeability due to shear dilatancy or cracking.
Furthermore, should cracks occur, the asphaltic concrete mix design should be such
that viscous creep and plastic flow will gradually close these cracks (self-healing
ability).
For a dam founded on bedrock the key to limiting the embankment deformations lies
in the material properties and in the compaction of the transition zones and sup-
porting shells (shoulders). If the embankment is founded on compressible soil over-
burden, differential distortions due to unequal settlements under the embankment are
likely to occur both across and along the valley.
Comparison with and evaluation of field measurements from existing dams combined
with finite element analyses, is the best way to predict the deformations and distor-
tions in new structures (Kjaernsli et al., 1992), The probable ranges for important
parameters should be included in the analyses to smdy the sensitivity of the numeri-
cal predictions to uncertainties in the embankment and foundation properties,
The stress and strain levels in the core, estimated from finite element design ana-
lyses, are used when modelling the behaviour of the asphaltic concrete in the labora-
tory. The laboratory specimens are subject to conditions approximating those that
will exist in the field, and the behaviour is studied with respect to degree of dilatancy
and increase in permeability, ductility and cracking resistance, stiffness and strength,
and self-healing ability after a crack has formed.
55
Fig. 6.1 The thin asphaltic concrete core adjusts to the deformations in the
embankment (from the construction of Storvatn Dam)
The fact that the properties of asphaltic concrete can, within fairly wide limits, be
tailored to satisfy specific design requirements, is an important aspect and advantage
of the method of using bituminous cores in embankment dams.
In finite element stress-strain analyses, which do not properly model the time-
dependent, viscous behaviour, it is difficult to assign appropriate, equivalent defor-
mation moduli for asphaltic concrete. The values strongly depend on temperamre
and strain rate during loading. However, a non-linear analysis approximated by
linear steps simulating the embankment construction sequence, is still very useful in
design and in interpreting field deformation observations. When one uses a formul-
ation based on concepts from the theory of elasticity. Young's modulus (E) and
Poisson's ratio are commonly specified for the different materials in and under the
embankment, Asphaltic concrete may then, depending on the mix, be assigned a
fairly low E-value to partly account for the viscous creep behaviour. However, the
bulk (volumetric) and one-dimensional moduli for asphakic concrete are high, as
there is very littie air in the pores which are virmally filled (samrated) with bimmen.
Thus, the analysis requires that Poisson's ratio be specified close to 0.5 or the bulk
modulus be given explicitiy as an input parameter. Failure to recognize this may
lead to significant underestimation of stresses in the core.
6.1.1 Typical core design
As described in Chapters 4 and 7, the core and adjacent filter/transition zones are
placed in approximately 0.2 m thick layers and compacted simultaneously during
56
construction. This construction procedure gives the hot asphaltic concrete immediate
lateral support and close interlocking along the core-filter interface. The contour of
that interface is not smooth but jagged as observed in situ after placement and com-
paction (Fig. 6.2). This is caused by the slight squeezing of the hot asphalt at the
base of the layer and bulging at the top.
<È
\ /
\ /
\ /
\ /
Fig. 6.2 Core cross section after placement and compaction
The core thickness may be decreased from core base to top, usually in steps of
0.1 m. For the Storvatn Dam described in Chapter 5, the base width was 0.8 m
and the top width 0.5 m. Modern construction equipment may produce a gradual
tapering, not stepped, if that modification in procedure is found economical.
Among the existing large dams with compacted asphaltic concrete core, the minimum
core width, in the top portion of the embankment, is 0.4 m. The maximum thick-
ness so far used is in a 105 m high dam in Hong Kong where the bottom portion is
1.2 m wide. An undocumented rule-of-thumb has evolved which calls for a core
thickness at any level of at least 1 % of the head difference between the upstream and
downstream sides of the core at that level. With modern construction procedures
and quality control this seems an unduly conservative practice for high dams,
Norwegian experience suggests a minimum core thickness of 0.5 m, and no more
than 1.0 m should be necessary, unless there are very special circumstances, for
instance in extreme earthquake regions or for embankments on compressible, erratic
foundations.
ICOLD Bulletin 84 (1992) states that an upward tapering of the core, as so often
practised, cannot be recommended "due to the multiple stressing to which the imper-
vious element is subjected". In high dams, and where the cost of bitumen and
asphaltic concrete production is significant, this practice would lead to an unreason-
able additional cost not warranted from a safety point of view.
57
The core is given a central position in the embankment. The core in Storvatn Dam
(Chapter 5) has a downstream slope 5:1, but the highest dam now under construc-
tion, the Storglomvatn Dam (Chapter 3), has been given a vertical core. The
additional construction and material costs of using a sloping core do not seem
warranted. Although a sloping core gives the advantage of producing a favourable
transfer of the water load to the downstream shell, a vertical, central core is subject
to smaller shear stresses. A vertical core is also somewhat easier to repair by
grouting than an inclined core, in the unlikely event that cracks should occur and
repair be required. Boreholes may then be drilled in the upstream filter zone and
grout injected to seal the leakage once it is located.
It does not seem necessary or advantageous to incline the top portion of vertical
asphaltic concrete cores in high dam as so often practised.
In a narrow V-shaped valley with steep flanks, and especially if the embankment is
resting on a compressible soil overburden, cross-valley arching will be significant
and should be analyzed. In the design analyses one should check the stresses in the
plane of the core and evaluate the shear distortions, dilation and potential cracking
that may occur.
6.1.2 Filter/transition zone
There is a practical limit to the combined width of core and filter/transition zones
that may be placed simultaneously by the asphaltic concrete placing machine. The
outer parts of the transition zones may therefore have to be placed independently by
other equipment. The minimum width of the filter/transition zone placed simultane-
ously with the core should be no less than 1.0 m.
The filter/transition zone should preferably consist of crushed hard rock with maxi-
mum grain size 60 mm, d^Q > 10 mm and d,5 < 10 mm. Crushed, angular rock
usually gives somewhat more stable support to the core and placing machine than
naturally rounded gravel. The transition material should have stretched gradation
curve, and one must regularly monitor and control the grain size distribution. The
difference in grain size between aggregates in core, in filter/transition and adjacent
supporting shell must not be too great. ICOLD (1992) gives the following guideline:
dioo ^ d,o and d,oo ^ '/4d,oo

core trans. trans. shell
Some designers recommend the addition of fine grain materials to the upstream
filter/transition zone. The reasoning is that if a defect exists or a crack opens in the
core, the transport of fine particles into the defect will reduce the leakage until the
viscous, plastic flow of the asphaltic concrete causes self-healing. However, it may
also be argued that the migration of fine particles into the crack will impair the
healing and be detrimental in the long run.
During extreme earthquake shaking, the core may be partly sheared off due to large
displacements in the top portion of the embankment (Section 5.4). The leakage rate
through the core will then depend on the width of the sheared zone, its depth below
58
reservoir level, and the permeability of the filter/transition zones next to the core.
For such an extreme event, k would be beneficial to have added fine-grained
material to the filter zones to reduce the leakage rate until the reservoir level can be
lowered and repairs executed.
6.1.3 Supporting shell
For an embankment dam resting on a stiff foundation, the materials in the transition
zones and supporting shells, the degree of compaction and uniformity, and the
steepness of the dam slopes govern the deformations and distortions imposed on the
thin core. For dams on compressible foundations additional displacements and
differential movements are imposed and must be estimated and accounted for.
Kjaernsli et al. (1992) present field deformation measurements for a number of

embankment dams and point out the effects of compaction equipment and energy
input, construction layer thickness, water content for earth materials and rock size
and water sluicing for rock materials, to reduce embankment deformations during
and after construction. A slow and gradual reservoir filling gives the core time to
adjust to this change in loading and any unpredicted, non-uniform deformations that
might arise. Thus, the simultaneous embankment construction and filling of the
reservoir, which the central asphaltic core method allows, is beneficial from a
technical as well as economical point of view.
It is recommended to place an especially well compacted zone on either side of the

filter zones, as done for Storvatn Dam (Zone 4a in Fig. 5.2) and the other dams
presented in Chapter 3. Water sluicing, in addition to vibratory compaction of
layers with moderate thickness, is usually specified for these zones to increase the
deformation modulus.
For a well compacted embankment of good rockfill resting on bedrock, the dam
slopes may be as steep as 1:1.3 to 1:1.4 as demonstrated by for instance the
Finstertal (Pircher and Schwab, 1988) and Storvatn Dam (Chapter 5). Even so, the
measured maximum displacements inside these two approx. 100 m high dams are
very small (of the order 0.5 m) and the strains in the core far below allowable
levels. The measurements agree quite well with the deformations computed by
corresponding idealized finite element analyses.
For a given situation the designer may, to accommodate potentially large core dis-
tortions, have decided to use a particularly soft asphaltic concrete mix, super-
saturated with a high bitumen content (see Section 6.2). The shear resistance of the
asphaltic concrete will then be low. This must be considered when analysing the
stability of the slopes of the supporting shells, especially if the embankment is
founded on a soil foundation (overburden) which may develop excess pore pressures
and reduced effective stresses and strength during potential earthquake shaking.
59
6.2 Asphaltic concrete mix design and properties
Standard asphaltic concrete core mix design criteria have been developed and, with
relatively small variations, used for most of the recentiy built dams of this type
(ICOLD, 1992). The aggregate composition complies with Fuller's gradation curve
(Fig. 6.3) improved with a fine grain component smaller than 0.075 mm (filler
material). Thereby the grain sizes from filler, sand and crushed rock or natural
gravel usually lie between 0 - 16 or 18 mm. In order to increase the workability and
compactibility, naturally rounded sand is often added with a gradation which com-
plies with the Fuller curve approximated by the equation:
P. = [j^] 100%
where pj is the percent by weight smaller than the equivalent grain size dimension,
100 ,....
90 /rr;^
1-
I ,
o 80
LJJ /
5 70 ii
> i / ;,1
m RO
1-
7^
LU SO . / z/ i
Ü
cr
III 40 .^< / ^ /3
*•^
•
a. ^^>^
CO 30 ^
z
cn
fO
?0
rr^
^.
C- - - ' ' ....-•"
<
a. 1U
0
0.075 0.25 0.5 1.0 2.0 4.0 8,0 16.0 32,0 64.0
PARTICLE SIZE (mm)
Fig. 6.3 Fuller's gradation curve for asphaltic concrete aggregates
The bitumen content is usually a littie higher than just sufficient to theoretically fill
the voids between the aggregates, and thus a close to maximum density is achieved
during compaction. This would typically correspond to a bitumen content of 5.5 -
6% (of total weight), and the mix is then easy to place and compact to the required
air void content of 3% (of total volume) or less. At this void content (porosity) the
asphaltic concrete has been found, through extensive laboratory testing, to be practi-
cally impervious even under high water pressures (Kjaemsli et al., 1966; Bikar and
Haas, 1973; Breth and Schwab, 1979). Above 3% the permeability increases fairiy
rapidly, and at 6% the permeability coefficient is about 10"^ m/s (Fig. 6.4). Labora-
60
tory Marshall tests on the specified design mix should be required to show a volume
of air voids less than 2% to account for the difference in degree of compaction
achieved in the laboratory and in the field, respectively (see Section 6.3.1).
Laboratory tests on asphaltic concrete with the same bitumen content, 6.2%, and
aggregates, but of different grain size distributions, show the importance of satis-
fying the Fuller curve criteria within reasonable margins. Figure 6.3 presents two
grain size curves beneath the Fuller curve. Asphaltic concrete using curve 3-material
could not be compacted to an air void content < 3%, it was relatively pervious,
exhibited brittle behaviour and had the lowest strength of the three mixes. Asphaltic
concrete using the Fuller curve and the same bitumen content was practically imper-
vious, had the highest strength, was ductile and showed the greatest ability to sustain
tensile and shear strains before cracking. In order to make an impervious asphaltic
concrete with curve 3-material, a significantiy higher bitumen content would have
to be used.
10-12
10-11
\
A
10-10
<)
03
CO 10-9
F o
o, 10-8 \
>-
_i 10-7
y
m v° °
< 10-6
° \
?
LU
cr 10-5
LU
n K\ ° 3
10-4 o 00
o o
10-3
10-2
o 2 4 6 8 10 12
AIR VOID CONTENT (%)
Fig. 6.4 Permeability of asphaltic concrete as function of air void content

(after Iâernsli et al., 1966)
6.2.1 Aggregates and flUer
The quahty of aggregates is classified using standard testing procedures (e.g. Asphalt
Institute, 1979; Statens Vegvesen, 1983) to determine flakiness and brittieness
indices. The indices are measures of aggregate particle shape and mechanical
resistance when subjected to a falling mass from a prescribed height. Only the
aggregate grain sizes between 8-16 mm are used for this purpose (Fig. 6.5). A high
flakiness index indicates elongated particle shape, and high impact value indicates
a brittle crushable aggregate.
61
70
60
KL,5
KL,3 KL4
LU SO
=3
1
<
> KL,2
•••
40
1- •
()
<
Q. KLI •
30
20
10
1.20 1.40 1.60
FLAKINESS INDEX
Fig. 6.5 Quality testing of aggregates where KL.l (Class 1) indicates highest
quality (after Statens Vegvesen, 1983)
The acceptance criteria are adopted from road pavement engineering and may in
some respects be unnecessarily strict. Once in place, the aggregates in a dam core
are not exposed to abrasion, weathering and significant temperature changes as are
road pavements.
On the other hand, the asphaltic concrete in the core for a high dam may be exposed
to very high stresses. In a relatively dry asphaltic concrete mix, say bimmen content
less than 5 %, the contact stresses between aggregates of low strength (quality) may
cause cracking and create flow paths for the water and increased permeability
through the core. This may put requirements on the aggregate quality as discussed
below. In a supersaturated mix, say bitumen content above 7%, there will be less
contact between aggregate grains, and aggregate quality and increase in permeability
may not be of concern.
The effects of aggregate quality on the stress-strain behaviour of asphaltic concrete

at stress levels corresponding to those in very high embankment dams, were recently
studied (NGI, 1992). Triaxial, strain-controlled, compression tests were performed
on cylindrical specimens 100 x 200 mm. The lateral stress, £^3, was kept constant
while the axial stress, ffj, was increased such that the axial strain rate was constant
at 2%/hour. The temperamre was held constant at 5°C throughout the test, and
three different levels of oj (confining stress) were used 0.5, 1.0 and 2.0 MPa.
Three different types of aggregates were used, classified as very good to poor:
crushed gabbro, crushed gneiss and crushed limestone (shale). These aggregates
correspond to quality classes 2, 3 - 4 and 5 in Fig. 6.5, which shows results for the
crushed gabbro.
62
Table 6.1 presents three asphaltic concrete mixes, which were all designed with a
bitumen content corresponding to maximum dry density, following the Marshall la-
boratory compaction procedure, plus 0.1% (Tests 1 - 9). The aggregate grain size
distribution satisfied Fuller's criteria. The differences in bimmen content in the
mixes are due to small differences in the grain size distribution curves, grain shapes
and the affinity of the aggregate surface to bitumen. The table also presents key
results from the triaxial testing.
Table 6.1 Different asphaltic concrete mixes tested in triaxial compression

(axial strain rate 2%/h, testing temperature 5°C)
Young's
Con- Axial modulus
Test Aggre- Bitu- Bitumen fining stress at 2 (secant
gate men content stress, failure, at at value at
No. type type 03 "1 failure failure 1% axial
(%) strain)
(MPa) (MPa) (MPa) (MPa)
1 Crushed B60 5.6 0.5 4.7 2.10 9.4 280

gabbro
2 (very 860 5.6 1.0 6 2.50 6.0 290
3 good) B60 5.6 2.0 8.6 3.30 4.3 290
4 Crushed B60 5.9 0.5 4.6 2.05 9,2 290
gneiss
5 (good) 360 5.9 1,0 6 2.50 6.0 300
6 860 5.9 2.0 8.7 3.35 4.3 300
7 Crushed 860 6.0 0.5 4.2 1.90 8.4 250
limestone
8 (poor) 860 6.0 1.0 5.5 2.25 5.5 270
9 860 6.0 2.0 8.5 3.25 4.3 260
10 Crushed 860 8.0 1.0 4.4 1.70 4.4 110
gneiss
11 (good) 860 8,0 2.0 6.0 2.00 3.0 110
12 Crushed 8180 5.9 1.0 4.3 1.65 4.3 140

gneiss
13 (good) 8180 5.9 2.0 6.0 2.00 3.0 90
The resulting stress-strain curves at corresponding levels of confining stress show

little difference among the three asphaltic concrete mixes. All curves showed plastic
yielding behaviour after the maxunum shear stress was reached, without any strain-
softening. This is due to the relatively high confining stresses used compared to
those in earlier tests reported in the literamre. At an axial strain of 1%, the secant
value of Young's modulus for Oj = 2.0 MPa, was 290 MPa for the mix with the
best aggregate and 260 MPa for the mix with the poorest aggregate. There was
63
somewhat more volume expansion (dilatancy) for the former as the shear stresses
increased and failure was approaching.
Young's modulus for asphaltic concrete shows little increase with increasing con-
fining stress. This is in contrast with results from triaxial samples of the aggregate
alone, which show a modulus increasing markedly with increasing a^.
The compressive strength values for the three mixes differed very little. The
strength of the mix with the poor aggregate (Tests 7 - 9) was only slightly lower than
for the very good aggregate mix (Tests 1 - 3) as shown in Table 6.1 and Fig. 6.6.
LEGEND (see Table 6,1)

• Gabbro (B60, 5.6%)
A Gneiss (B60, 5.9%)
O Limestone (B60, 6,0%)
« Gneiss (B60, 8.0%)
D Gneiss (B180, 5,9%)
CO
CL
co
G
I
3 4 5 6 7 8 9 10 11 12
1/2 (Oi +CT3) (MPa)
Fig. 6.6 Strength of different asphaltic concrete mixes determined from tri-
axial compression tests
In conclusion, the difference in quality of the aggregates tested in this study had little
effect on the asphaltic concrete stress-strain-strength behaviour.
However, aggregate flakiness has effect on the content of bitumen required in a mix
to obtain the specified low porosity and hence permeability. The series of Marshall
tests performed to determine the optimum design mixes with the three aggregate
types clearly demonstrated this. At a bitumen content of 5.5%, the mix with the
gabbro aggregate had a significantly lower porosity than the mix with the limestone
aggregate with higher flakiness index.
Typically the total weight of fine-grained material smaller than 0.075 mm (filler)
constimtes 12% (Fig. 6.3), Of this about half may be added fines in the form of
64
Portland cement or crushed limestone to supplement the fines recovered from the
mechanical crushing of aggregates. The maximum allowable quantity of fines taken
from the crushed aggregates themselves, depends on the acidity of the aggregates and
must be evaluated in each case (Section 7.2.6).
6.2.2 Effect of bitumen content and viscosity
In most dams so far built with compacted asphaltic concrete core, the bimmen con-
tent has been somewhat higher than that required for optimum density achieved in
Marshall compaction tests. The aggregate grain size distribution has in all recent
dams satisfied the Fuller curve within reasonable margins. Depending on the type
of aggregate, flakiness, mineral composition and surface characteristics, exact grain
size distribution and viscosity of bimmen, this will commonly lead to a bitumen
content in the range 5.5 - 6.5% by total weight of asphaltic concrete mix.
A lower bimmen content leads to an asphaltic concrete mix which is less workable,
more difficult to place and compact, and it will be more pervious. A higher bitumen
content makes for a softer mix which has more pronounced viscoelastic-plastic
properties, has lower stiffness and strength but is less pervious.
High shear stresses imposed on asphaltic concrete may lead to shear dilatancy and
volume expansion. Figure 6.7 shows the degree of dilatancy as a function of bitu-
men content (type B80) and axial strain in triaxial compression tests as described in
Section 6.2.1. The results are plotted for two different confining stress levels and
clearly show the reduced dilatancy with increasing bimmen content. Furthermore,
as is reasonable, the dilatancy is reduced when the confining stress is increased. For
a bimmen content of 8% there is virtually no volume change for the test with low
confining stress and actually a volume reduction for the higher confining stress.
Z) 1 I 1 ' ' 1 1 1 1 I ' 1 i 1 L-

Q O 2 4 6 8 10 0 2 4 6 8 10
>
VERTICAL STRAIN (%)
Neg. vol strain = Expansion
Fig. 6.7 Degree of dilatancy as function of bitumen content (after Breth and
Schwab, 1979)
5. Asphaltic -
65
The dilation causes an increase in p)ermeability due to the opening of small fissures,
although no visible cracks may appear. Therefore, the increase in permeability may
become much larger than the increase in volume would indicate, because the shear
strains and resulting dilatancy may have caused fissures that interconnect.
This has been demonstrated by permeability tests on specimens first tested in triaxial
compression (NGI, 1985). In the regions of high shear strains along the failure
plane, smaller samples were cut out of the triaxial specimens. These small samples
were in turn tested in a permeameter. Although the volumetric strain during dilation
only amounted to 1 - 2% expansion, the permeability coefficient showed an increase
by a factor of 10^ - 10^. This increase can only be explained by a set of communi-
cating fissures (cracks). However, the increase in permeability only occurred as
fissures opened for shear deformations close to the failure level (strength) for the
asphaltic concrete. No significant increase was detectable until about 80% of the
strength was mobilized.
To study the effect of increasing the bitumen content on deformation modulus and
strength, additional triaxial tests were run on asphaltic concrete specimens with the
crushed gneiss aggregate in Table 6.1. The bitumen content was increased from
5.9% to 8% in Tests 10 and 11. The same strain rate (2%/h) and temperature (5°C)
were specified as for the previous tests. The secant deformation modulus at 1%
axial strain and 0-3 = 2 MPa was reduced from 3(X) MPa to 110 MPa, and the shear
strength was reduced from 3.35 MPa to 2.00 MPa (Fig. 6.6). Furthermore, a small
volume contraction rather than dilation occurred, in agreement with the results
presented in Fig. 6.7.
To study the effects of reducing bitumen viscosity, but keeping the bitumen content
at 5.9%, supplementary triaxial tests were performed (Table 6.1). Bitumen type
B180 was used rather than B60. The results from these tests (Tests 12 and 13) with
5.9% B180 were very similar (by coincidence almost identical) to those obtained for
8% B60 both with respect to stress-strain behaviour and strength (Fig. 6.6 and
Table 6.1).
These new laboratory tests, and others reported in the literature, demonstrate that the
properties of the asphaltic concrete mix may be designed to satisfy specific engi-
neering requirements for a given situation. The potential extra costs of achieving
special properties, for instance by increasing the bitumen content, must in each case
be compared with the benefits in terms of safety and reliability.
Recent field tests in Norway demonstrated that even with a low-viscosity soft
bitumen (B180) and a content as high as 8%, the placing equipment and procedures
described in Chapter 4 could be successfully applied. However, when the bitumen
content exceeds 10%, one gets a supersaturated "flowable" asphaltic concrete which
cannot be effectively compacted. Section 2.1 briefly discussed hand-placement
procedures and use of shutters for such high bitumen contents.
66
6.3 Laboratory testing of asphaltic concrete
The asphaltic concrete mix design is based upon experience from extensive surface
pavement research and engineering. In addkion to the standardized Marshall method
(see below), supplementary tests have been and are being used to evaluate and
document the suitability of an asphaltic concrete mix for use in a dam core. This
is particularly important where the engineering properties of the asphaltic concrete
are tailored to satisfy specific core design requirements.
6.3.1 Marshall method of mix design
The Marshall method (Asphalt Institute, 1979) uses standard shaped specimens 64
mm (2'/2 in) high and 102 mm (4 in) in diameter, prepared using a specified pro-
cedure for heating, mixing, and compacting the bitumen-aggregate mix in a mold.
The two principal features of the Marshall method of mix design are a density-voids
(porosity) analysis and a stability-flow test of the compacted test specimen.
The density-voids analysis corresponds to the Proctor procedures for determining

optimum water content for earth core materials in embankment dams.
The Marshall stability-flow test is performed by radially loading the disc shaped
specimen at 60°C. The load is applied through semi-circular testing heads at a
constant displacement rate of 51 mm/min until failure occurs. The stability number
is the maximum load resistance recorded in units of force (N). The flow value is
the total radial deformation that occurred in the specimen between no load and
maximum resistance.
Typical results from applying the Marshall method plotted as function of the bitumen
content, are presented in Fig. 6.8. These are the results from the asphaltic concrete
mix with the high quality gabbro aggregate described in Table 6.1.
6.3.2 Triaxial testing
The use of triaxial tests to determine properties of asphaltic concrete is illustrated in

Section 6.2.1.
Norwegian practice has been to use samples 100 mm in diameter and 200 mm high.
The aggregates for the mix are first preheated for 4 hours at 160°C and the bimmen
for 2 hours at 145°C. At a temperature between 150 - 160°C the mix is placed in
5 cm thick layers in a preheated triaxial mould with inside diameter 100 mm. Each
layer is compacted for '/a min. by a method similar to the one used for Marshall
specimens. The indicated temperatures are for use with bitumen type B60. For
bitumens with lower viscosity (like B180) somewhat lower temperamres are used.
The tests are usually run strain-controlled at a specified strain rate and temperature.
Common reference values used are 2%/h and 5°C. Most tests have been run as
axial compression tests, but different stress paths may be followed to best model
field conditions for representative elements in the core. Results obtained are stress-
67
strain behaviour, dilatancy as function of imposed shear stress and strain, shear
strength as function of confining stress, shear strain when the strength level is
reached, and whether the sample exhibits ductile or brittle behaviour.
2.72
2,71
CO 2
2,70
E LU
\-
3
> Z
O
2.69
b o
CO
z 2.68 g
O
LU >
Q cc
2.67
<
2.66
4 .5 5,0 5.5 6.0 6.5 7.0 4,5 5.0 5.5 6,0 6,5 7.0
Bitumen content (%) Bitumen content (%)
11000
10000
z 9000
Ë 8000
i 7000
O
6000
5000
4 ,5 5.0 5.5 6.0 6.5 7,0 5 5,0 5.5 6.0 6,5 7,0
Bitumen content (%) Bitumen content (%)
Fig. 6.8 Typical results from the Marshall method of testing
6.3.3 Permeability testing
Typical results from permeability testing are shown in Fig. 6.4.
In principle the permeameter may look like the one illustrated in Fig. 6.9, where the
specimen is sealed against the sides of the container by a bitumen layer and rests on
a porous base. More elaborate test set-ups, where the sample is subjected to known
horizontal and vertical stresses like in a triaxial test, may also be used.
As described in Section 6.2, specknens may be cut from triaxial samples subjected
to significant shear distortions, to measure the permeability as function of dilation
and internal fissuring (cracking). The degree and rate of self-healing and permeabi-
68
lity reduction with time, due to viscous, plastic flow, may be studied as function of
bimmen content and type.
Water under
pressure
Burette
Bitumen seal —
Asphaltic concrete -
specimen
Filter plate
Fig. 6.9 Permeability testing
6.3.4 Resistance to cracking under flexure
In pavement design, small test beams are being used to study the behaviour in
flexure and the ability of the asphaltic concrete to undergo extensional strains without
cracking.
In Norway a simple plate bending test has been developed to study the suitability of
different asphaltic concrete mixes for use in a dam core (Fig. 6.10). The situation
"simulates" in a way local bending in the core due to differential deformations in the
embankment or locally reduced support from the downstream filter/transition zone.
A disc shaped specimen 300 mm in diameter and 60 mm thick is supported inside
the walls of a cylindrical pressure chamber. The specimen is sealed with bitumen
around the edges to prevent any leakage between the upper and lower part of the
chamber. The upper part is filled with water, and the pressure under the plate may
also be controlled.
The test is usually run by applying an overpressure in the upper chamber, for
instance 500 kPa, which is kept constant, and the central deflection of the plate is
measured as a function of time. The gradual opening of fissures increases the
permeability and the leakage through the sample, and a sudden increase in leakage
occurs when cracks penetrate the plate. As for the triaxial tests described in Section
6.3.2, the tests are commonly run at 5°C.
The behaviour of different mix compositions is compared by looking at the

deflection-time curves and the magnimde of central deflection tolerated before water
break-through. Typical results for the asphaltic concrete mixes described in
Table 6.1 are shown in Fig. 6.11. There is only one test for each mix, so the
available data set does not justify general conclusions. However, the results show
significnat differences in deflection rate and magnitude of break-through deflection
for mixes with bitumen types B60 and B180, respectively.
69
Pressure
Water under
pressure
Bitumen
seal
Asphaltic concrete
plate specimen
Fig. 6.10 Sketch of the NGI plate permeameter
50 -
X Gneiss (6180,5,9%)
E 40
Ê.
Z
O
H
O 30
m
_i
u.
LU
Q Gabbro
_l 20 (B60, 5.6%)
<
h-
2
LU
Ü
10 X - water broke through
Testing temperature 5 °C
< 1 1 L ^
0 2 4 6 8 10 12 14 16 18 20 22
TIME (HOURS)
Fig. 6.11 Results from plate permeameter tests
Alternatively, the plate permeameter experiments may be run deformation-controlled

by controlling the plate deflection rate with time.
70
Chapter 7
Construction - Contract and Work Specifications
7.1 Contractual aspects
The general contractual terms presented by Federation Internationale des Ingénieurs
Conseils (FIDIC, 1992) are recommended, and ICOLD's Bulletin 85 (1992) contains
very useful guidelines concerning contracts for dam construction work.
7.1.1 Basic contract considerations
Norwegian practice favours the use of a flexible type of contract based on risk
sharing between owner (client) and contractor as illustrated in principle in Fig. 7.1.
Furthermore, the contract is based on unit prices, where the quantity listed for each
item of work is estimated at the tender stage and is calculated when the work is
finished.
Owner's risk Contractor's risk Project cost

0% 100%
Turnkey
Lumpsum
Optimum Fixed price
Lump sum —
Price escalation
Target estimate
Cost reimbursement
100% 0%
Fig. 7.1 Risk sharing according to type of contract and assumed influence on
project cost (after Kleivan, 1988).
There are in principle two philosophies for the preparation of tender documents: the
result-oriented and the operation-oriented contract type. In the result-oriented model,
the documents specify the requirements which must be fulfilled by the end product.
In the operation-oriented contract model, the client specifies the work operations
which have to be performed, and the contractor calculates the unit prices based on
those specifications.
With the result-oriented type of contract one may encounter difficulties in reaching
agreement on change in price if the client should want to alter the design during con-
straction. This is because the various work operations chosen by the contractor to
achieve the results required in the tender documents may be different from the ones
best suited to satisfy the altered design, and the differences may not have been
defined in advance.
71
In the operation-oriented model a formal work procedure must be specified to
achieve satisfactory field control of the materials which are placed and compacted
in a continuous process. In case of alterations in design or operation, both owner
and contractor must have experienced representatives present who can make binding
decisions at the site, without causing undue delays in the progress of other aspects
of the dam constmction.
The discussion presented below presumes that the contract considered herein com-
prises only the asphaltic concrete core and the adjacent filter zones. Thus, the con-
tractor for these works has either a subcontract with the general dam contractor or
a contract with the owner as one of many coordinated contracts for the dam con-
struction. As illustrated by the case study in Section 7.2, Norwegian practice for the
construction of asphaltic concrete cores is a contract which in effect uses elements
of both the result-oriented and operation-oriented model.
7.1.2 Prequalification, quality assurance and control
The critical importance of the thin core in a zoned embankment dam, where all the
different construction processes are so interdependent, requires an experienced and
resourceful contractor. It is therefore necessary to practice stringent prequalification.
If a contractor cannot refer to earlier asphaltic concrete works on embankment dams,
he will only have the opportunity to participate in the competition by demonstrating
through field tests his ability to produce, place and compact the asphaltic concrete
in a prescribed manner. He must document that his field personnel is experienced,
knowledgeable and prepared to cope with problems should they arise during con-
struction.
To ensure the intended quality at all times, it is necessary to have a comprehensive

and coordinated quality assurance and control system (QA/QC). This applies to the
client as well as the contractor. Since regular reporting is a comprehensive task for
the contractor, it is recommended to include this as a cost item in the Bill of
Quantities.
With strict quality control during production, transportation and compaction, it is

rare that asphaltic concrete acmally built into the core does not meet the require-
ments. If so happens, the unacceptable material has to be removed and replaced
unless the contractor can execute other acceptable remedial measures without dam-
aging any other parts of the dam. The contractor should describe potential methods
of repair in his tender bid.
7.1.3 Price adjustment
In accordance with the contracmal spirit of risk sharing between owner and con-
tractor, the unit prices should be adjustable in conformance with the general changes
of the price level. This is especially relevant for contracts lasting over several years,
which is common in the case of embankment dams.
72
The work with the core is subject to the same price adjustment procedures as those
used for other parts of the embankment. In Norway, a price index for rockfill dams
has been practised for several years, and that has been found very convenient. Prior
to this practice the price adjustment procedure in heavy construction was an onerous
task because of its complexity and the many factors to be taken into account. The
escalation of the price was greatiy influenced by the way the items of reference were
specified in the bid and how each factor was credited. In order to simplify and
standardize the procedure, the hydroelectric power industry therefore took steps to
establish price indices applicable to each of the following: rock tunnels, under-
ground power stations, concrete dams, and rockfill dams. It was not found possible
to arrive at one index common to all these structures.
For the bitumen in the asphaltic concrete mix and for the heating oil used for drying
aggregates, the prices will not vary according to the domestic, but to the inter-
national market. Therefore, there may be special price adjustment clauses for
bitumen and heating oil.
7.2 Work and material specifications - a case study

As an example of how work and material specifications are formulated in practice,
elements of the specifications for the asphaltic concrete core and filter zone for the
125 m high Storglomvatn Dam (Fig. 7.2) are presented below.
3-5. 591+Ah
• 2.6
Bedrock surface
Grout curtain
Fig. 7.2 Storglomvatn Dam
7.2.1 Asphaltic concrete mix design assumed when preparing tender
A fairly soft and rich asphaltic concrete mix is specified to achieve the desired engi-
neering properties and core behaviour. The bitumen type is B180, and the content
6. Asphaltic -
73
is 6.3% (of total weight). The bitumen content of random samples must not deviate
more than ±0.3 percentage points from this specified value.
Gravel taken from the specified location at Holmvatn should be used as aggregates.
The grain size distribution must satisfy the Fuller criteria within the margins speci-
fied below:
Grain Size (mm) Weight (%)
8 - 18 28
4 -8 18
2 -4 13
0.075 - 2 28
0 - 0.075 (filler) 13
The grain size distribution for random samples of the asphaltic concrete mix must
lie within the following margins from the mean values presented above:
± 6% for grain size > 2 mm
± 4% for 0.25 mm < grain size < 1 mm
± 3% for grain size = 0.125 mm
± 2% for grain size = 0.075
50% of the aggregates should consist of crushed Holmvatn gravel.
The filler material (< 0.075 mm) may consist of a combination of fines from the
crushing of aggregates and added fines from other sources. The added fines must
consist of either crushed limestone, cement or other material accepted by the client.
The maximum allowable quantity of fines taken from the crushed Holmvatn
aggregates, depends on the acidity of the gravel and is subject to clients's approval,
but should not exceed 50% of the total filler mass.
7.2.2 Modifications to basic mix design proposed by contractor
The mix design specified in Section 7.2.1 is documented in the report from the
Norwegian Geotechnical Institute (NGI, 1993). This design is based on gravel
materials from the Holmvatn location available at thetimeof laboratory testing. The
laboratory asphaltic concrete mix contained aggregates of natural gravel mixed with
50% crushed material from gravel sizes larger than 18 mm. The filler material
consisted of 1/13 crushed Holmvatn gravel and 12/13 crushed limestone.
The contractor is required to perform his own tests using the aggregates, crushing
and mixing equipment at the site. The results from these tests may be somewhat dif-
ferent from those obtained by NGI in the laboratory due to differences in aggregate
properties, scale of operation, crushing techniques and asphaltic concrete mixing pro-
cesses. The results must be documented and reported with the contractor's proposal
for modifications to the mix design presented in Section 7.2.1. Any modifications
are subject to the client's approval. Any subsequent changes in mix design during
core construction, including the filler used, are subject to the client's approval.
74
7.2.3 Prequalification of contractor
Prior to contract agreement, the client may require that a contractor, with no satis-
factory references from earlier similar work, demonstrate his ability to simulta-
neously place core and filter materials with the equipment he plans to use on the
dam. The demonstration includes the placing of two layers, each 0.20 m thick, with
the width of core equal to 0.5 m. The costs for this demonstration must be included
in the tender bid.
7.2.4 Test production and placing of asphaltic concrete on site
Test production and test placing of asphaltic concrete on site is required prior to start
of construction. The asphaltic concrete used must be according to approved mix
design, and the production and placing equipment the same as that to be used during
subsequent construction. The core (zone 1) and filter (zone 2) should be placed in
the same way and widths as in the dam.
The results of the test production and placing must be reported by the contractor and
approved by the client before construction can start. The report must include the
results of the material investigations specified in Section 7.2.6.
7.2.5 Requirements to plant and equipment
The asphaltic concrete mixing plant must have the capacity to produce the volume
required for two layers placed within 24 hrs. The plant production should be con-
tinuous while the placing machine (crawler paver) operates.
A fully automatic batch plant must be used with a computer printout to show the pro-
portioning for each batch. The computer alerts the operator if the proportions are
outside the preset limits, and the plant must then stop automatically. At all times the
temperatures of the aggregates, bimmen and final mix must be automatically con-
trolled.
A production flow diagram must accompany the tender bid. The contractor must
control all scales and production equipment at least once a month and always before
the start of a new construction season.
The placing machine must be of such design that the placing process may be ob-
served visually. In front the machine must be equipped with a vacuum cleaner to
soak up any water and dirt on the existing asphaltic concrete surface. Behind the
vacuum cleaner a heater must be mounted to heat the existing layer immediately be-
fore a new layer is placed. However, the asphaltic concrete surface must not be ex-
posed to open flames. All parts of the placing machine in contact with the asphaltic
concrete must be preheated prior to start of placing. A principle sketch of the
machine must accompany the tender bid.
Three self-propelled, smooth, vibratory rollers, must be used to simultaneously

compact the core and the adjacent filter/transition zones. The roller for the asphaltic
75
concrete must have a width equal to or no more than 0.10 m wider than the core.
The minimum weight of the rollers used for filter compaction is 1.5 t. The core is
compacted by light rollers to achieve the required in-situ void content < 3 %.
The contractor is required to establish a field testing laboratory of sufficient capacity

to do all the routine testing (Section 7.2.6) within specified reporting deadlines. The
laboratory investigations must satisfy the guidelines presented by Statens Vegvesen
(1983). Subject to prior agreement between contractor and client, the tests on the
bitumen itself may be done and reported by the supplier.
The contractor must present a QA/QC-plan for the production specifying the names
of persons responsible for the different control routines. The plan is subject to
approval by the client.
7.2.6 QA/QC and reporting during construction
Bitumen
• The bitumen type is specified as B180. The penetration value must be between
145 and 210 at 25°C for a penetrating mass of 100 g in 5 s.
• For each new delivery of bitumen supply to the plant, the following properties
must be reported:
Standard required
- penetration ASTM D5-73
- viscosity ASTM D2171-66/72
- failure point (Fraas) DIN 1995/1960
- ductility ASTM 113-76
- density ASTM D70-72
Aggregates
• The aggregates for the asphaltic concrete must satisfy the grain size requirements
specified in Section 7.2.1.
• The impact value and flakiness index for the aggregates must be less than 60 and
1.45, respectively. Tests on the Holmvatn gravel have shown these criteria to
be satisfied, but the contractor is required to run independent tests at regular
intervals during construction to document the quality of the aggregates.
• Special tests have shown that the adhesion between bitumen and Holmvatn gravel
is good (Riedel value 8 - 9 ) . However, the contractor is required to run
independent tests once a month during construction to document that the
adhesion is satisfactory. The test method must be acceptable to the client.
• The requirements to the filler material (< 0.075 mm) are presented in
Section 7.2.1. The organic content of the fines resulting from the crushing of
aggregates, must be controlled weekly before the fines may be accepted for use
76
as filler material. The "colour intensity" must be ^ 2 when tested by the
NaOH-method (Statens Vegvesen, 1983) The aggregates must be stored and
protected against contamination.
Asphaltic concrete production
• Aggregates must be dry but have temperature not exceeding 200°C.
• Temperature of asphaltic concrete mix must not exceed 160°C.
• The client's QC representative must be informed when scales or temperature

controls on the automatic plant are adjusted.
• Asphaltic concrete produced with incorrect proportions or outside specified tem-

perature limits must not be transported to the dam core.
Asphaltic concrete from plant
• Extraction analyses must be performed on four asphaltic concrete samples per

day to determine the bitumen content and the grain size distribution of aggre-
gates. The sampling must take place at roughly regular intervals during the pro-
duction day.
• Compaction of Marshall test specimens for daily control of consistency and air
voids content.
Asphaltic concrete compacted in core
• Core drill samples must be taken as soon as the asphaltic concrete temperature
allows sampling. One core sample must be taken for each four layers placed,
or at least one per week of production. Each core must be drilled through two
layers (i.e. 0.40 m). The core is cut into approx. 50 mm long pieces, and the
following properties must be determined:
- specific density of asphaltic concrete
- specific density of aggregates
- grain size distribution of aggregates
- bitumen content
- air voids content
The core drill boreholes must be filled with hot asphaltic concrete and compacted
immediately after sampling.
• In addition', the contractor is required to continuously control the air voids con-
tent for each layer placed by means of a non-destructive test method (e.g. use
A requirement on this particular project, as the owner (The Norwegian Energy Corporation)
wants to further develop the non-destructive control method for subsequent projects.
77
of isotopes). The contractor must in his tender bid describe the non-destructive
test method and procedures which are subject to approval by the client.
In case irregularities appear in the data from any of the control tests, they must
immediately be reported to the client's QC representative, who may require addi-
tional tests, at no cost to the client.
7.2.7 Requirements to core placing and compaction procedures
Transportation, placing and compaction of the asphaltic concrete require special

equipment. The field work must satisfy the guidelines presented by Norwegian
Asphalt Association (1980) unless stated otherwise in these work specifications.
During compaction the temperature of the asphaltic concrete must be between 140°-
155°C.
If the temperature during placing exceeds 155 °C, the mass must be allowed to cool
before compaction can start.
The asphaltic concrete is to be placed and compacted in 0.20 m (± 0.03 m)

horizontal layers. The air void content must be less than 3% (of total volume) after
compaction. Requirements to compaction equipment are presented in Section 7.2.5.
Zones 1 and 2 must be placed simultaneously, with zone 1 slighüy ahead of zone 2.
During compaction the two zones must be of approximately the same height and be
compacted with three vibratory rollers run in paralleP.
No more than two layers of asphaltic concrete (i.e. 0.40 m) may be placed in 24 hrs.
A third layer may be placed if the contractor can document the in-situ quality also
of this third layer after compaction.
Zones 1 and 2 must at no time be built up to a height more than 0.40 m above the
level of zone 3 (see Fig. 3.1), which, on the other hand, must not be more than
0.40 m above zone 2.
The interface between concrete sill (plinth) and base of asphaltic core should be
covered with a 10 mm thick layer of mastic. The concrete surface must be clean and
dry and may have to be sandblasted and/or washed with hydrochloric acid to pro-
mote good adhesion (bond) between concrete and mastic. The concrete surface must
be heated prior to the application of mastic at a temperature of 150°C. The width
of the mastic strip along the sill must be at least 0.50 m wider than the base of the
asphaltic core, and mastic must fill the space around the special construction joints
in the concrete sill. The waterstop must be made of material that can stand the heat
from the hot mastic.
^ See Fig. 4.4
78
Elev. m.a.s.l.
r= 587 586.95+Ah Minimum width of core and filter
m.a.s.l. Core Core base Zone 2

bi(m) b2(m) (m)
Ah = camber
above
537 0.5 1,0 1.50
„ ^ 537-elev 3.5-b,
537-517 bi +0.5
"'"' ' 100 2
below 537-etev. 3.5-b,
bi +0.5
517 °- ' 250 2
470
o 0.5 1.0 m
MINIMUM CORE WIDTH (b^)
Gore base and foundation

sill under river bed
Dam axis
D(m) a (-)
0-1.5 <90
1,5-3.0 S60
>3.0 <45
Core base and foundation

.1.0m
sill at elev. 500
Water-stop .,
in construction I b3-6,0m
joints I
Min. sill Min. sill

Dimensions of concrete
m.a.s.l, width, b i thickness, 1 foundation sill
(m) (m)
above
537 4.0 0.50
537 - 505 5,0 0.75
below
505 6.0 1.00
Fig. 7.3 Details of core and foundation sill design
79
The two first layers of asphaltic concrete on top of the mastic strip must have the
width shown in Fig. 7.3. At locations along the valley floor and at the abutments
inaccessible to the placing machine, hand placement procedures must be used. For
this purpose shutters must be employed, and the requirements to temperature control
and maximum allowable air voids content after compaction are the same as for
machine placing.
During construction the width of the core in place must be checked by direct
measurements when required by the clients's QC-representative. Effective horizontal
width on the interface between two subsequent layers must be equal to or larger than
the minimum width specified on Fig. 7.3. Furthermore, the distance from the
theoretical centerline to the upstream or downstream side is required to be at least
half the specified width at that elevation.
To ensure proper bonding between subsequent layers, the interfaces must be clean,
dry and preheated prior to placement of the next layer. Temporary bridges must be
built for vehicles to cross the core during construction.
If the weather conditions are such that the placing and compaction procedures do not
meet the requirements, the construction process must be discontinued. The client's
QC-representative can require work stoppage.
If any asphaltic concrete as placed and compacted does not meet the specified
requirements outiined above, it must be removed without causing any harm to other
parts of the core already built. Such removal and repair work is not reimbursed for.
7.2.8 Requirements to filter/transition zone
Natural gravel from the Holmvatn borrow area should be used for zone 2, which
must consist of well graded masses with grain size 0 - 6 0 mm, djg > 10 mm and
di5 < 10 mm. This zone must be placed and compacted simultaneously with the
core to provide immediate lateral support to the hot asphaltic concrete. Zone 2 is
placed in its full design width (Fig. 7.2) and compacted as described in Section 7.2.7
with 3 - 6 passes of a roller of minimum weight 1.5 t. The amount of compaction
has to be adjusted on site as it depends on the properties of the filter material.
The contractor is required to control the grain size distribution of zone 2 by sampling
at least once a day. A report must be submitted to the client's QC-representative
once a week.
7.2.9 Unit prices
The tender bid must be expressed in terms of unit prices for zones 1 and 2, respec-
tively.
Core
Specify price per m-' of asphaltic concrete placed and compacted in core. The price
must include the costs of all operations and materials related to production, transport-
80
ation, placement and compaction, laboratory testing, quality control and reporting.
It must include the laying of mastic and special hand placement required. The reim-
bursement is based on theoretical (design) core width and the measured contour pro-
file of the top of the concrete foundation sill across the valley.
Filter
Specify price per m^ of Holmvatn gravel placed and compacted in zone 2. The price
must include the costs of all operations such as work in the borrow area, crushing,
screening, transportation, laboratory testing, quality control and reporting.
81
References
Adikari, G.S.N., T. Valstad, B. Kjaernsli, and K. H0eg (1988)

Behaviour of Storvatn Dam, Norway. A case of prediction versus performance.
Proceedings 5th Australia - New Zealand Conference on Geomechanics, Sydney,
Australia. (Also presented in Norwegian Geotechnical Institute Publication No. 173,
Oslo).
Amevik, A., B. KjaemsU, and S. Walbo (1988)

The Storvatn Dam. A rockfill dam with a central core of asphaltic concrete.
16. International Congress on Large Dams, San Francisco, R.9-Q.61. (Also
presented in Norwegian Geotechnical Institute Publication No. 173, Oslo).
Asphalt Institute (1979)

Mix design methods for asphalt concrete and other hot-mix types.
Manual Series No. 2, The Asphalt Institute, College Park, Maryland.
Bikar, R. and H. Haas (1973)

Untersuchungen über den Einfluss der Dichte auf Wasserdurchlassigkeit von
Asphaltbetonen.
Strabag, Schriftenreihe Nr. 9, Cologne.
Breth, H. and H.H. Schwab (1979)

Zur Eignung des Asphaltbetons fur die Innendictung von Staudammen.
Wasserwirtschaft 69, Heft 11, pp. 348-351, Stuttgart.
Clough, R.W. and R.J. Woodward III (1967)

Analysis of embankment stresses and deformations.
Journal of Soil Mechanics and Foundation Engineering, ASCE, Vol. 93, SM4,
pp. 529-549.
FIDIC (1992)
Conditions of contract for works of civil engineering construction.
Federation Internationale des Ingénieurs-Conseils, 4. edition, Paris.
Gazetas, G. and P. Dakoulas (1992)

Seismic analysis and design of rockfill dams: state of the art.
Journal of Soil Dynamics and Earthquake Engineering, Vol. 11, pp. 27-61.
Haas, H. (1983)
Zur Eignung und Optimierung von Asphaltbeton fur Kemdichtungen in Staudammen.
Bitumen, Heft 3, pp. 97-106, Hamburg.
Hveding, V. (1992)
Hydropower Development in Norway.
Norwegian Institute of Technology, ISBN 82-75598-012-7, Tapir, Trondheim.
82
ICOLD (1992)
Owners, consultants and contractors.
International Commission on Large Dams, Bulletin 85, Paris.
ICOLD (1992)
Bituminous cores for fill dams.
ICOLD (1982)
Bituminous cores for earth and rockfill dams.
KjaemsH, B., T. Valstad, and K. Hoeg (1992)

Rockfill Dams - Design and Construction.
Norwegian Institute of Technology, ISBN 82-75598-012-11, Tapir, Trondheim.
Kjaemsh, B., J. Moum and I. Torblaa (1966)

Laboratory tests on asphaltic concrete for an impervious membrane on the Venemo
rockfill dam.
Norwegian Geotechnical Institute Publication No. 69, pp. 17-26, Oslo.
Kleivan, E. (1988)
Norwegian tunnelling contract system.
Norwegian Soil and Rock Eng. Assoc., Publication No. 5, pp. 67-72.
Lysmer, J., T. Udaka, C.F. Tsai, and H.B. Seed (1975)

FLUSH - A computer program for approximate 3-D analysis of soil-structure
interaction problems.
Earthquake Engineering Research Center, Report EERC 75-30, University of
California, Berkeley.
Makdisi, F.I. and H.B. Seed (1978)

Simplified procedures for estimating dam and embankment earthquake-induced
deformations.
Journal of Geotechnical Engineering, ASCE, Vol. 104, No. GT7, pp. 849-867.
Moiseev, I.S., N.N. Yakovlev, A.L. Goldin, L.V. Gorelik and V.G. Radchenko
(1988)
Rockfill dams with asphalt concrete diaphragms.
16. International Congress on Large Dams, San Francisco, R.62-Q.61.
Newmark, N.M. (1965)

Effects of earthquakes on dams and embankments.
Geotechnique, Vol. 15, No. 2, pp. 139-160.
Norwegian Asphalt Association (1980)

Guidelines for design and construction of bituminous pavements (in Norwegian).
Ingenierforlaget, Oslo.
83
Norwegian Geotechnical Institute (1992)
Asphaltic concrete cores for embankment dams - laboratory triaxial tests.
NGI Report 530106, Oslo.

Storglomvatn Dam - asphaltic concrete mix design (in Norwegian).
NGI Report 736013-076, March 10, Oslo.

Laboratory investigations of asphaltic concrete.
NGI Report 68601, Oslo.
Pircher, W. and H. Schwab (1988)

Design, construction and behaviour of the asphaltic concrete core wall of the
Finstertal Dam.
16. International Congress on Large Dams, San Francisco, R.49-Q.61, pp. 901-924.
Seed, H.B. (1979)

Considerations in the earthquake-resistant design of earth and rockfill dams.
Geotechnique, Vol 29, No. 3, pp. 215-263.
Statens Vegvesen (1983)

Laboratory investigations. Design Manual 014, Oslo (in Norwegian).
US Committee on Safety Criteria for Dams (1985)

Safety of dams: Flood and earthquake criteria.
National Research Council, National Academy Press, Washington DC.
Valstad, T., P.B. Seines, F. Nadim and B. Aspen (1991)

Seismic response of a rockfill dam with an asphaltic concrete core.
Water Power and Dam Construction, April, pp. 1-6. (Also presented in Norwegian
Geotechnical Institute Publication No. 184, Oslo).
84
Index
A Clay core lo
Abutment 21, 38, so Climate ii, 14, 29, 42-43, so
Acceleration 51, 52 Colour intensity test 77
Acceptance criteria 43, 62, 73, 76 Compaction 13, 14, 19, 33, 41-42, 55, 59, 75-
Accidental leakage 52 80
Acidity (acidic) 30, 65 Concrete,
Added filler 64 deck 10,37
Adhesion 34, 76, 78 gallery 39
Adit 39, 41 sill 20-27, 33-34, 39-41, 78-79
Admixture (additive) 34, 41, 76, 78 Confining stress 62, 64
Aggregate 61-65, 74, 76 Construction,
Aging 14 equipment 15, 29-30
Air void content (porosity) 34, 42,43, 60, joint 78-79
61, 68, 77, 78 procedure 15, 33-35
Alluvial deposit 13, 15, 59 season 11, 14, 20,42
Alignment 38, 39 Contamination 77
Alta River 12 Content,
Ambursen type 10 air voids 19,32,43,60-61,77-78
Appurtenant strucmre 49 bitumen 13, 15, 18, 36, 61, 63, 65-66, 74, 77
Arching 56, 58 filler 18, 30, 36, 60, 74, 76
Arch dam 10,12 Contract specifications, 7i
Arctic Circle 20 operation oriented 71-72
Asphaltic concrete mix 18, 42, 60-66 result oriented 71-72
Asphalt mastic 34, 78 Contractor 71
Aurland scheme 11 Core,
base (slab) 4i, 80
B bimminous 13
Backhoe 19, 42 bridge 35, 80
Batch plant 29-30, 42, 75 clay 10
Berdalsvatn Dam 22 concrete lo
Bitumen, concave 38
content 13, 15, 18, 36, 61, 63, 65-66, 74, 77 convex 35, 38
density 76 drilling 36, 43, 77
ductility 76 inclination 21, 41, 57
penetration 76 silt 10
seal 68-69 sloping 21, 41, 57
type 18, 66 thickness (width) 14, 17, 18
viscosity 14-15, 65-66, 76 width (thickness) 14, 17, 18
Biasj0 reservoir 9, 37 Cost,
Blocks 19, 42 construction 37, 41, 71
Bonding 78, 80 project 37, 41, 71
Boreholes 39, 41, 58 reimbursement 71, 80
Borrow pit ii, 14,37, 80 total 71
Brittle behaviour 68 Cracking 14, 51, 55, 59, 68-70
Bulk modulus 56 Cross section 20-27, 40-42, 73
Crushed,
C gravel 18
Cement (Portland) 37 limestone 18, 30, 63, 65, 74
85
rock 10, 19, 37-38 Finite elements 45,51,55-56
soft rock 10 Finstertal Dam 45, 48
Crushing plant 30, 36, 42, 75 Fissures (cracks) 14, 68-70
Cyclic, Flakiness index 61-62
loading 49-52 Flexure 69-70
strains 52 Flow value 67
Flowable concrete 13, 66
D Foundation,
Dam, compressibility 13-15, 20, 55, 57, 59
alignment 38, 39 grouting (injection) 20-27, 34, 39, 41
crest 10, 20-27 stability 13-15, 55, 59
height 10-12, 17-18, 20-27 Fuller's curve 18, 44, 60
volume 20-27
Deformations 14, 20-27, 45-48, 51-52, 55-56,
59 Gabbro 62-64, 67, 70
Density 60, 67-68, 77 Gallery (adit, mnnel) 20,39, 4i
Design, Glacial till (moraine) lo-ii, i4, 25, 37-38
analyses 37-42, 49-53, 55-59 Gneiss 38, 62-64, 70
conditions 9, 13-14, 37-42, 49 Gradation 18, 44, 52, 58, 60, 74, 77, 80
earthquake 14, 49 Grain size 16, 18-19, 44, 52, 58, 60, 74, 77, 80
mix 18, 42, 60-70 Granite 38
Differential settlement 13, 15, 55, 66 Gravel 18-19, 58, 74, so
Dilatancy (volumetric expansion) 14, 64-66 Grout,
Displacement 20-27,45-48,51,55,59 curtain 20-27,39
Distortion 14, 45-48, 64-66 grouting 20-27, 34, 41
Ditch (trench) 34, 39, 79
Drainage capacity 52 H
Ductility 14,61,66,68,76 Hand placement 13, 33-34
Dynamic analysis 49-53 Hauling distance 33, 37, 42
Heater 31, 73, 75
E Holmvatn Dam 12, 17
Earthquake, Hydrochloric acid 34, 78
acceleration 5i,52 Hydropower 9
coefficient 49-50
region 14, 57 I
resistance 14, 49 Impact index 61-62
shaking 49, 59 Impervious element lo, 37
Taft 51 Inclined core 2i, 4i, 57
Elasticity theory 45, 50, 56 Inclinometer 44
Embankment dam lO Infrared heater 3i
Equipment, Instrumentation (field) 44
compaction 33, 75, 78-79 Inspection (quality) 36, 43, 72
construction 15, 29-33, 75 Isotope 36, 44, 77
Extensional strain 38
Jersey, U.K. 29
Factor of safety 49-50 Joint,
Field measurements 20-27, 44-48, 55 construction 78-79
Filler 16, 18, 30, 61, 64-65, 74 rock 34, 41
Filter (transition) 15, 19, 32, 58, 78-81
Fines (filler) i6, 18, 30, 6i, 64-65, 74
86
K P
Karst 20, 41 Parameters,
Katiavatn Dam 17, 18, 25 design 18, 42, 55, 60-66
mix 18, 42, 60-66
L Particle size 16, 18-19, 44, 52, 58, 60, 74, 77,
Landscape (environment) ii, 14 80
Langavatn Dam 17, 18, 27 Paver (placing machine) 13, 15, 29-32
Laser 31 Penetration (bitumen) 76
Layer thickness (lift) 13, 15, i9, 43,78 Permafrost 11
Leakage 14, 44-45, 52, 60-61 Permanent displacement 50-51
Limestone 18, 30, 62-63, 65, 70, 74 Permeability,
Lump sum, 7i coefficient 45, 60-61, 66
fixed price 71 increase 14, 60, 62, 66
price escalation 71, 72-73 permeameter 68-69
Placing machine 13, 15, 29-32
M Plant 29-30, 42, 75, 77
Marshall test 64-65, 67-68, 77 Plastic flow 14-15, 65, 66
Mastic (asphalt) 34, 78 Plate permeameter 69-70
Material specification, 73-78 Plinth (sill) 20-27, 33-34, 39-40, 78-79
admixmre 34, 78 Poisson's ratio 56
aggregate 74, 77 Porosity (air void content) 34, 42, 43, 60,
bitumen 76 61, 68, 77,78
filler (fines) 74 Prediction 44-53
Max. credible earthquake (MCE) 49 Prequalification (contractor) 72
Measurements (field) 21-27, 44-48 Price,
Mix, adjustment 71-72
design 18, 42, 60-66 fixed 71
parameters 18, 42, 60-66 Principal stresses 62-63
Modulus, Pseudo-static analysis 49-50
bulk 56
one-dimensional 56 Q
secant 63 Quality,
Young's 56, 63, 66 assurance 36, 43, 72
Mold (Marshall) 67 control 36, 43, 72
Monitoring (field) 21-27, 44-48 Quarried rock 19,38
Moraine core 10-11, 14, 25,37-38
Movements 44-48, 55-56, 59 R
Rainfall (precipitation) 14, 29, 42
N Repair 58, 80
Namral gravel 18-19 Result-oriented contract 71-72
Non-destructive test 36, 44, 77 Requirements (specifications) 7i, 73-81
Richter magnitude 49, 51
O Riedel value 76
Observed behaviour 12, 21-27, 44-48 Risk sharing 71-72
Oddatj0rn Dam 11 Riskallvatn dam 15, 17, 18, 24,30
Oedometer 45-46 Rockfill 10, 12, 15, 17, 19, 20-27, 37, 45, 52,
73
Operation-oriented contract 71-72
Operational safe earthquake (OSE) 49
S
Organic content 77
Safety factor 49-50
Sand blasting 34, 4i, 78
Scar 11, 14
87
Screed 30-31 flexure 69-70
Screening 36, 43, 74 Marshall 64, 67
Seismic, oedometer 45-46
acceleration 51, 52 permeability 68-69
analysis 49-53 plate 69-70
coefficient 49-50 Proctor 67
response 14, 49-53 triaxial 45-46, 62-68
Seepage 44-45 Transition zone 15, 19, 35, 41-42, 52, 58, 78-
Self-healing (sealing) 14, 55, 58, 68 81
Shear deformation 63-66 Triaxial test 45-46, 62-67
Shear strength 59, 62-64, 66 Toe drain 19, 20-27, 52, 73
Shutters 13, 33, 66 Tolerances 44, 74
Sill (plinth) 20-27, 33-34, 39-40, 78-79 Tunnel (grouting) 20, 39, 4i
Silt core lo
Sluicing (water) 19, 42, 59 U
Snow 14, 42 Underseepage 20-27,39-41
Specifications 71, 73-81 Unit price 72,80-81
Stability, Upstream facing lo, 37-38
analysis 55, 59
number 67 V
Stability-flow test 67 Vacuum triaxial test 46
Standard deviation 36 Vesterdalstjern Dam 17, 18, 26
Stearin acid 34 Vibratory,
Stone-bitumen method 13, 18 compaction 13, 14, 19, 33, 41-42, 55, 59, 75-
Storglomvatn Dam 12, 17, 18, 19, 20, 73-81 80
Storvatn Dam ii, 14, 17, 18, 36, 39, 56 rollers 19, 75-80
Strain, Virdnejavre Dam 12
-controlled 62, 70 Volume,
rate 62, 66 dam 20-27
Strength, expansion (dilatancy) 55, 58, 64-66
compression 59, 62-64, 66 Viscosity 14-15, 65-66, 76
shear 59, 62-64, 66 Viscoelastic-plastic 14, 55, 56, 65
Stress ratio 63
Styggevatn Dam 17, 18, 29 W
Sub-zero weather ii, 14, 29 Water sluicing 19, 42, 59
Supersamrated 59, 62, 65-66 Waterstop 78-79
Supporting shell (shoulder) 19, 55, 59 Weather conditions ii, 14, 29, 42-43, 80
Svartevatn Dam ii Workability 14, 65
Work specifications 73-81
T
Tack coat 31 Y
Tapering (of core) 17, 41, 57 Yield acceleration 5i, 63-64
Television monitor 31 Young's modulus (E) 56, 63, 66
Temperamre,
constraint 15, 16, 19, 69, 77-78 Z
control 15, 16, 19, 33, 34, 42, 63, 67, 69, 77- zone (embankment) lo, 19, 20-27, 41-42, 59,
78 73
Tender documents 42, 71
Test,
aggregates 61-62, 76
bimmen 65-66, 76
88

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A s p h a l t i c C o n c r e t e C o r e s for

Embankment Dams KAARFHÖEG

Asphaltic Concrete Cores

Experience and Practice

Cover plioto: Berdalsvatn Dam.

Bituminous cores may be built by different construction procedures, for instance by

Chapter 4 describes modern construction equipment and procedures, and Chapter 6

The Research Council of Norway (NFR)

Oslo, September 1993

Chapter 1 Norwegian Dam Building - Historic Review 9

Chapter 2 Merits of the Asphaltic Concrete Core Design 13

Chapter 3 Norwegian Dams with Asphaltic Concrete Core 17

Chapter 4 Norwegian Construction Equipment and Practice 29

Chapter 5 Case Study - The Storvatn Dam 37

Chapter 6 Design - Principles and Requirements 55

Fig. 1.1 The Blasje reservoir in mountainous West Norway

Systematic construction of embankment dams, mainly rockfill dams, began in 1924,

Height above Length Volume Comple-

Asphaltic concrete 1980

Plus two under construction (see Table 3.1)

A construction procedure which has been successfully applied in Norway on several

As a variation on the methods mentioned above, a different technique is presently

2.2 General merits of the asphaltic concrete core

Asphaltic concrete is virtually impervious, flexible, resistant to erosion and aging,

2.3 Core construction procedure

The asphaltic concrete is compacted at a temperature around 160°C depending on

Table 3.1 Norwegian rockfill dams with asphaltic concrete core

Height Core Vertical Volume

Vestredalstjem 32 0.5 1:0 6000 3100 1978-80 Selmer'VStrabag Oslo Energy

Katlavatn 35 0.5 1:0 4600 2300 1979-81 Selmer/Strabag Oslo Energy

Langavatn 22 0.5 1:0 3800 1900 1979-81 Selmer/Strabag Oslo Energy

Storglomvatn Statkraft/ Norwegian

Holmvatn Statkraft/ Norwegian

At the time the company name was Furuholmen

Remarks: • Chapter 6 gives the principles, procedures and terminology con-

(2) FUter/ Natural gravel or crushed 0.2 1.5 3-6"

(3) Transition Crushed rock, 0-200 mm 0.4 15 -1- water sluicing 4

(4a) Shoulder Quarried rock, 0-400 mm 0.8 15 -1- water sluicing 8

(4b) Shoulder Quarried rock, 0-800 mm 1.6 15 6

(5) Slope Selected, large blocks Individually placed - -

(6) Crown Selected, large blocks Individually placed - -

(7) Toe drain Selected, large blocks Dumped in lifts - -

Fig. 3.2 Storvatn Dam

Maximum height: 90 m Crest length: 1472 m Total volume: 9.5 mill, m^

Fig. 3.3 Berdalsvatn Dam

Maximum height: 65 m Crest length: 465 m Total volume: 1.0 mill, m^

The unusual zoning in Berdalsvatn as compared to Storglomvatn (Fig. 3.1) and

Fig. 3.4 Styggevatn Dam

Maximum height: 45 m Crest length: 600 m Total volume: 1.1 mill, m^

Maximum height: 35 m Crest length: 265 m Total volume: 0.2 mill, m^

.-•«•.. «ü. J '^i^mï^irr' -aR'StiSi

Fig. 3.7 Vestredalstjem Dam

Maximum height: 32 m Crest length: 500 m Total volume: 0.4 mill, m^

4.1 Asphaltic concrete plant

4.2 Core paving equipment

Fig. 4.3 Working principle for core paver

«iSKfo.- - •• .... - -r.^.,. :••• • .<^^,r*v<a,

Fig. 4.4 Simultaneous compaction of core and fdters

4.3 Placing and compaction procedm-es