COIVCRETT SOCIEIY" TECITrVICAL-?

APIIR "IvO1O5

F. A. Auld BSc, PhDictCflngi:,MIGE.t::,MIMi,f]E

;-;,iFFB
C h i e f D e sI , i sv r n
E n s i n e e. r .. ! . . j : . , r . , i j . , . , , 1 T
..
t: j
, i,,t{
.
,
)
\
'. .1,,.;.:
Cepg+teti,oq,.-lti+fdg, Linited,,
, - , , r , :j , . r i : j r
.j,-rn,l

,,ri5'-.'Afi

.',,:
r.ii

. jjrjl!:t,11!;

r;.ii,:ri:r,:ii

The Concrete Society,

Terminal

House,

i'r:ii

rllrt 1

i)r5

.t t it:

c j

ll'i.jir:::iirla'.:j-i:

r:-..lci;sb(r':'rixiltj

::
.-;-i tlt: j;l{ij.r:
l:;i:ifjldi.,'!
ajl iJ
- r , r r ' ; ' : r ; i ' i : . i , r i i : ! : f ) , : zi : t
ia i;tiIid;li

:!fvra)aw(rli,
i,9J,.l:rf f,c

. - .,

ir.'ir,r:il:r,l

i':l

, ,,, , \"t'" t:

)f,,t'-\1

illl.

i,:il.ir

:S"r;a::::'i;

Grosve,no.,_r:.
Gardens3e LortdonrSWilW!{
OA,JI-".)t.;a.il

The author wlshes to thank Mr J C Black, Managlng

Director
of Cenentation Hlnlng Linlted,
for
pernisslon
to present the paper.
Illustratlons
and
detalls
are included fron the Selby New Mine
Projecc and the author ls lndebted to
- Selby
(l{ining)
Mr C T Massey, Deputy Dlrector
Project,
of the Natlonal
Coal Board for his
pernisslon
to use thls lnfornation.
Further acknowledgenents are due to Mr V W llowe,
who was responslble
for producLng nany of the
illuscrarion
drawlngs, Cementatlon Mlnlng Llmitedrs
personnel for assistance
drawlng offlce
ln
detailing
others, Mrs J Slmpson for prLntLng che
illustratlons,
Mrs M Mordue for typlng the
manuscript,
and various colleagues in Cenentation
Mlnlng Linited
for supplying
the photographs.

Fronc cover photograph: Typical

shaft botton showing
Mount Isa Copper Mine,
actual worklng conditLons.
shaft A.10.S, Australia.

Concrete
Flrst

Soclety

publlshed

Technical
1983

Paper.No.

105

ISBN O 72LO T284 I

Publlshed
by The Concrete
Terninal
House, Grosvencir

Soclety
Gardens,

London SWIW OAJ

Designed and prlnted

by the Cement and Concrete
Association
Wexhan Springs,
Slough SL3 6PL
Further
copl-es nay be obtained
fron:
Publlcatlons
Dlstrlbutlon,
CeEent and Concrete
Assocl.ation
I{exham $prlngs,
Slough SL3 6PL
quotlng'reference
nunber 53.039
Price
@

Group CS5
fne Concrete Soctety

1983

Although The Concrece Soclety (linlted

by
guarantee) does lts best Eo ensure Ehat any advice,
recoomendation or lnfornat.ion
it nay glve elther
Ln
this publlcatlon
or elsewhere is accurate,
no
llablllty
or responsibility
of any kind (tncluding
ltablllty
for negllg6nbe),
howsoever and fron
lthaEsoever cause arislng,
ls accepted ln this
respect by the Soclety, lts servants or agenEs.

Goncretein
Unde$rorrnd.

Illorlcs

F. A. Auld BSc, PhD, CEng, MICE, MIMinE, FFB

Chief Design Engl-neer,
Cenentation Mlning Linited

Paper presented at The Concrete Society

Yorkshire and Hunberside Reglon.
One-day Synposlun, Concrete in power and
energy. Selby Fork Hotel, Yorkshire
18 Novernber1981

The paper covers three aspects of

concreting
in underground works.
In the first
section,
various types of
structure
are described to illustrate
the broad range of concrete
construction
work which is involved
in
mining development.
An indicatlon
of
general design principles
is also
included.
The secbnd section illustrates
the
means of carrylng
out the work.
Plant
and construction
techniques are
descrlbed in detall.
A discussion on mix design requirements
constltutes
the third aspect.
Included
i n t h i s s e c t i o n a r e c o m m e n E . so n t h e u s e
of cement replacement materials
and
admixtures.

eutfror's Introductory
wote onRecent and.
GurrentUndeground.
Worlcs Projects
Cenentatlon Mlnlng Linlted
have ln the last five
years been lnvolved
ln the conscructlon
of six
shafts (out of a total of ten) and tso drifts
for
the Natlonal Coal Board's New Mlne ProJect at Selby
ln Yorkshlre (see Figure 1).
Shaft depths range
from 417 to 1033 n.
The Gascolgne Wood drlfts
and
lwo shafts at WlsEow are norr complete, with the
other four shafts,
cwo at Rlccall
and two ar North
Selby, stlll
under constructlon
at the present
tloe.
AII the shafEs at Selby have been sunk uslng
the freezlng process to control water, the depths
of freeze ranging fron 148 to 283 n.
Cenentation
Mlning Linited
are also ready to conmence sinklng,
without freezlng,
a new 1023 ro deep shaft at Maltby
Colliery
for the NCB.
During the period 1963 to 1973, eight shafts were
sunk for Ehe potash nines ln Saskatchewan, Canada,
by The CeEentatlon Co. (Canada) Ltd., slx of then
to depths of over 1000 n nith freeze depths from
Many other shafts have been sunk
468 to 684 n.
over the last lwenty years tn various countrles
wiEh or sithout
freezlng.
In Gernany, sixteen
shafts have been sunk during the perlod using the
freezing pfocess, four of the@ current
contracts 1.
A total of thirty-one
shafts have
in Canada and Norrh Aoerica slnce
been constructed
1963 uslng fteezlng 2.
The Chinese have also sunk
rnore than seventy shafts, all frozen 3.
Annual lengths of 56 and 47.3 ko are quoced for
llned and unlined tunnels for the years 1979 and
a.
years
During the last fifteen
1980 respectlvely
LiEited
M
l
n
i
n
g
have been the
CeEentation
conEractors for che Alcan Snelter polrer staEion
coollng water intake and outfall
tunnels at
Lynenouth, the two Isle of Grain pouer staiion
coollng sater lntake tunnels and the single
Peterhead power station
cooling water intake
In 1978 they also completed the Edinburgh
tunnel.
effluent
oucfall
tunnel wiEh twenty dlffusers
!o
the sea bed ln Seafleld Bay.
At leasE two nore
such contracts are currently
ln progress by other
contractors.
for shaft, tunnel and
The future potential
is enormous.
underground constructlon
Access below
ground ls required for nany purposes: e.g:
nineral extraction;
power station and assoclated facillties
water tunnels and nachlnery halls);
reooval to the sea;
effluent
storage (gas, liquid or nuclear waste);
nuclear shelters.
Although aE the present tlne the world-vLde
econornic cllnate
is no! favourable
for such
developoent, nany furure najor projecEs are
inevltable.
F A AuId
October 1982

(cooling

References
[.

KLEIN, J.
Preaent 6tate of freeze shaft deslgn
Proc. of the Synposiun on Strata
ln nlnlng.
Mechanlcs, University
of Newcastle upon Tyne, 57 Aprl1, 1982. Elsevler Scientlflc
Publlshlng
Conpany, 1982. pp. 147-153.
BRAUN, B. and NASII, W.R. Ground freezLng
applicatlons
ln underground ninlng
Proc. of The Third Internatlonal
constructlon.
Synposiuro on Ground Freezlng.
US Arruy Corps of
Engineers Cold Reglons Research and Engln-eering
Laboratory, Hanover, New Hampshlre, USA. 22-24
June, 1982. pp. 319-326.
AULD, F.A.
Notes on vislt
of Cementation Mlnlng
Llnlted/Foraky
Llnited
Technlcal Delegatlon to
China, 3-15 October, 1979.

4 , CONSTRUCTIONINDUSTRY RESEARCHAND INFORMATION

ASSOCIATION. R.P. 307 - Pipe Jacking Phase 1.
Second Draft Report.
Chapcers 1, 2 and 3 and
Appendix A, B, and C. April,
1982.

Gontents
Page

I.Introduction

aIVI,es of Stnrcture and.

Generaf Desi$n FinciBles

2.r

Introduction

2.2

Shafts

2.2.I
2.2.2
2.2.3

Advantages of concrete in
shaft construction
Reinforcement
Design of shaft linings

6
6
6

2.3

Collars and foreshafts

2.4

Air and fan drifts

2.5

Insets

t0

2.6

Tunnels

l1

2.7

Spiral

I4

2.8

Sump tanks

16

2.9

Plugs

l6

chute bunker shafts

5. Construction MetJrod.s

t7

3.1

Introduction

17

3.2

Collars and foreshafts

t7

3.3

Air and fan drifts

IB

3.4

Shaft lining

r8

3.5

Insets

')L

3.6

Tunnels

zo

3.7

Spiral

28

3.8

Sump tanks and plugs

2B

3.9

Batching plant

2B

chute bunker shafts

3.10 Transportation

and placing

3.10.1 TransportatLon down shafts

3.10.2 Transport underground
3.10.3 Concrete placing at roof level

2B
29
29
29

4. Goncrete llltix Design

30

4.1

Introduction

30

4.2

Normal mixes

JU

4.3

Cementreplacement materials

3l

4.4

Admixtures

3l

5. Gonclud.lng Remarks
33
6. Eeferences
34
7. GlossarJr of llfiining Terms :s

l.Introdustion

Conflned spaces present access, handllng and

pJ.acing problens and. for developnent sork in
wlth plt
exlsElng pits,
its use oust not interfere
productlon.
Nevertheless, wLch a correclly
plant and a
englneered handling systen, the rlght
sulEable nlx deslgn, concrecLng underground Ls noE
difficult.

Concrete and steel are the two najor construcElon

naterlals
used in underground developnenc work.
Steel ls nornally
enployed ln the forn of arches or
square work (colunns and beans), fabrl.cated fron
Archee or square sets roay be
standard secElons.
used as pen0anent support to an excavatlon or as
temporary supporE prLor to provlding
a peroanenE
Except in extrenely
concrete structure.
competent
ground, or Ln ground whlch can
and self supportlng
be supported by rock bolts and nesh, steelwork
cenporary support, prlor Eo llning
ln concrete, ls
essential for safe working 1n underground
excavations.

Thls paper concentrates

on three naLn aspecte of
with concrete.
underground constructlon
Flrstly,
which can be
lt illustrates
the types of sfructure
found ln such an envlronnent.
Also lncluded are
general deslgn prlnclples
for such strucL.lrfes.
The
second section descrlbes how construcBlon work of
Flna1ly, concrete Dlx
thls kind is carried out.
deslgn requirenents are lndlcated.
In che latter
secllorr,
the use of cenent replacement Eaterlals
and adnlxt.ures ls conmented uDon.

UsLng concrete underground creates addltlonal

problens to Ehose encountered above ground,

a IIrI,es of Stnrcture and, @neral Desilfn Pr'rnciples

To put the use of concrete underground lnto
perspective,
i! trust be reroeobered Ehat the nlning
environment ftnposes lts own special conditlons.
Allied rllth any excavation ls a conslderatlon of
two naJor faclors:

2.1 Introductlon
In sinple terms, underground development work
(see
lnvolves chree distincc
stages of operatlon
Figure l).
For a new nine, the first
stage ls the
sinklng of a shaft or an lncllned
drift
to reach
the level of the proposed underground
developnent.
Secondly, horizontal
or nearly
horlzontal
tunnels are drlven Eo the extractlon
partlcular
face of the ore body.
Thlrdly,
areas
along the drivage are enlarged to house equipoent
and other productlon facillties.
The constructlon
of other underground structures which are required
is also lncluded in this last sEage. Figure 2
shows nany of the structures
to be found ln a nlne.

(a)
(b)

Goscoigne \{ood

\4)

Wistow

rn
v

S t i l l i n g ft e e t

R i c c ol l
Whilemoor

)
Fiiure
4

Norlh Setby

1.

New mine construcElon

the developnent

the excavatlon

once lt

presence of waEer ln

is

large

If the studies indicate the presence of large

quantlties
of lrater, then pre-treatoent
by grouting

%r

of

Eoth of these aspects can be studted prlor Eo

excavation, using geologlcal and hydrogeologlcal
borehole data, and the trethod of ground pretreatnent can be esrabllshed.
Provlded the waler
inflow is low lt can be handled entirely
by dlrect
punping or wlth the asslstance of a well dewaterlng
scheme.

CivlI englneerlng
shaft sinking and tunnelllng
work
is carrled out in sinllar
stages to that for a new
mlne.
Existlng plt developnent ls purely an
extenslon of facllitles
on the saoe basis.

The stabllity
opened up,
The possible
quantities.

of

the

Selbv Coalfield.

LEGEND
(1)

Heodfrome

@ dSiksicphhoorigsetsi ny gs toenmd

o
@
o
@
o

S h o ft c o t t o r
Fqndrift
Ventilotion fqn
Shoft furnishing
Shoft tining

Insets

Roodwoyjunc

Bunker shqfts

( 1 1) S k i p t o o d i n gp o c k e t

@ P u m pc h o m b e r
@ S u m pt o n k
@ bSuotfkeht yepqtddu og owr i t h
@
Figure

2.

Mine structures

and operaEional

facilities.

S p i t t o g er e m o v q t

tray be necessary to reduce the Lrater nake lnto the

Groutlng ls the process of lnjecting
excavatlon.
cement, or other materials, to ioprove the strength
of the strate or to retard or prevent the passage
of liquids or gases. For excesslve anounts of
water ln conditions where the ground is not
susceptible
to grouting,
freezing techniques can be
considered.
The freezlng process is a long
establlshed method of consolidatlng
water-bearing
strata to prepare it for shaft sinking,
ln which a
freezing agent (usual1y brlne) is circulated
through suiEably disposed boreholes drilled
into
the strara around the site of the shaft. Sitrllar
technlques can also be employed in the horizontal
direc!ion for tunnels.
It ls lriEhin thls envlronnent
that concrete must be
transported
and placed underground.
Full knowledge
1s therefore essenEial of the behavlour of concrete
ln all chree phases of 1ts installation,
ln fhe weE
sEater during lnitial
settlng and in the fully
hardened conditLon.
The Eethod of excavating is an added factor
to be
consLdered when uslng concrete underground.
Blastlng is nornally ernployid and its effects on
early age concrete at close range EusE be
acconnodated.
The subject of blascing effecrs on
early age concrete ls a conplex one and ls
therefore outside the scope of thts paper.
In addiCion to ground treatment, the lining of an
excavation can also be designed prior to
construcEion by enploying.rock
and soil mechanlcs
prlnclples
Eo deternine ground pressures or on the
basls of the liningrs
ablliEy to reslst hydrostatic
pressure.
Concrete linlngs in thls context can
either be purely cosnetlc where lhe ground is selfsupportlng;
they nay be constructed after
lnscalllng
steelwork temporary support; or the
design could necessitate rapid lnstallation,
lnnediately
upon openlng up the excavation,
to
ground movement.
nlninize

2.2 Shafts
A typlcal
shaft sectlon is illustrated
in Figure
together with the geology and esElmaEed water
lnflows needed for ground pre-treatment
analysis
and shaft linlng
deslgn.

2.2.1

Advantages of concrete
construction

in

3,

shaft

The choice of concrete as a shaft Lining material

is easily Justlfled.
Relatively
small areas of
wall can be constructed systematlcally
in phase
wlth the shaft slnklng process. Transport to any
positlon in Ehe shaft is slnple by neans of
pipellne or skip.
Concrete is a convenlent
naterLal
to handle and place r.r1lhin fhe restricted
worklng space of a olne shaft.
When placed,
concrete moulds itself
to Che excavated profile
of
the shafE provlding
an inEerlocking
action with the
surrounding rock.
TesEing procedures for concrete
quality control are straightforward.
Resistance to
sulphate attack is achieved by using sulphate
resisting
Portland cenent, producing a structure
whlch requires little
naintenance.
Unrelnforced concrete can wlthstand most loading
conditlons noroally encountered and 1t produces a
dry'shaft.
Ttre benefits of using concrete,
partlcularly
unreinforced concrete, for shaft
Iinlngs are therefore substantial.

2.2.2 Reinforcement
SEeel rel"nforcement is used only ln spectal
clrcunstances,
where weak strata occur, to provide
reslstance to localised
tenslle bending stresses
and as a means of preventing fragmentatlon of the
concrete,
However, steel reinforcenent
which has
Co be included ln a shaft wal1 could be subject to
corrosion whlch could cause spalllng.
In addicion,
t.here is a probleo ln fixing
the relnforcement
and

so, ln general, it ls preferable

unrelnforced concrete.

2.2.3

Design of

shaft

to use

linlngs

The deslgn of concrete shaft linings is discussed

roore ful1y in other papers r,z.
Stresses in a
thlck cyllnder
can be deternlned eicher on an
elastlc
design basis or by an ultinate
linlt
state
principles.
approach eoploying plastlclcy
In Ehe
case of a shaft ln conpetenE (self standing when
excavated) rock, the deslgrr of the llning
need only
pressure through the aquifer
cater for hydrostatlc
zones.
The thlckness of the llnlng
is therefore
varied with depth until
a level ls reached at which
sater is no longer present and only a noninal
thlckness of concrete becones necessary.
Mlgratlon
of wacer downsards fron the hydrostatic
sectlon ls
prevented by lnstalllng
grouc seals at the'botEon
of the hydrostatlc
llnlng.
In ground which ls
lncompetent,
rock pressures may need to be
consldered as an alternatlve
to hvdrostatic
Pressure.
The mlninun thickness
for a concrete shaft linlng
ls norually
300 nn unless che concrete is belng
cast. dlrectly
agalnst frozen ground, ln shich case
600 oo should be the mlnLroun. Wlth thls extra
thickness of concrece sufflcienc
heat is generated
by the hydratlon
of Ehe cenent to overcome any
detrloental
effects due to freezing of the
concrete.
Increnents of wa1I thickness of 150 nm
are generally used, up to a naxlnum of 1200 m, at
which thlckness constructlon
becones
lnpractlcable.
Speclfied characteristic
srrengths
for shaft linlng
concrete range from 25 N/mm2,
shlch is che loser limit
for dense, watertight,
structural
concreEe, up to 45 N/mn2, thls being the
pracEicable upper llnit
bearing in urtnd the
conflned condltions of placing.
However, wiEh
appropriaEe nix ingrediencs and by using
workablllty
agents and good quallty control,
sErengths greater than 45 N/nurz are possible.
Lining of the shaft takes place downwards in 6 m
lengths as slnklng proceeds.
PVC grout seals
(Flgure 3) are provided at each construction
joint
and couplete natertightness
ls achieved using a
backwall grouting process.
Fron Figure 3 it can
joint in any
also be seen that at each horizontal
frozen sectlon a slot is lefE at the inside face
which can be gunlted after conpletlon
of heave
durlng Ehe freezing period.
Guniting is carried
out ftnmediately the cenperaEure of the llnlng
rlses
above 0"C in the thawing period.
The cribs shown
ln Figure 3 provide additlonal
support for the
seight of the lining
Ehrough softer zones but
norrnally the weight is assumed to be transferred
directly
to the surrounding rock.

2.3 Collars

and foreshafts

Positloned aE the top of the shaft llnlng

ls the
(see Figure 3).
collar and foreshaft structure
This is constructed in relnforced concrete (see
Figure 4).
The total length of Ehls section, froo
collar
level to the botton of foreshaft
will
vary
depending upon the ground condiEions.
Wal1
thlcknesses are normally greater than for the
upper sectlons of the shaft lining.
Figure 5 ls
a vlelr
looking down a finished
collar
and
foreshaft.
The purpose of the collar and foreshaft ls
twofold.
Its maln function ls to provlde a rigid,
Ioad carrying strucCure whlch passes through the
soft, surface soil deposlts and transfers the
headframe and other collar loads to the hard,
conpetent rock below.
In other words it performs
the funcEion of a large dlameter plle.
The
secondary function of the collar and foreshaft
section is to give sufficlent
initial
depth of
shaft co enable the installation
of the slnking
stage to be carried out prior to the Ealn
excavation.

OE
I STIHAT
WATER
STRATA
TOUN.
INFLOTd
. LINES
DH A F T

FREEZE
6LACIAL

F
L
I

tn
]U
e
o
L

FROZENI\

zoNri

2273to227)0

EUNTERSANOSTONE
( 500to5000)

FREE
ZE
TUBES

UPPERPERMIAN
MARL
STANOARD

UPPER
MA6NTSIAN
LIMESTONE
MIDOLE
PERMIAN
MARL
LOWER
MA6NESIAN
LIMESTONE
LOWER
PERMIAN
MARL

lll
ll7
t7l.
175
t 1 6 BASALSANOS

tt:l

ffi-;ffir;r',-,

Vl;l

l"k

'{ ol
X+:,

BRTERLY
RorK;:+;'i
}i+t90

ffi
f-F)vt

ll --- - - . 1

|- .-J
A C K W O RRTO
HCr-:-:+KL:;J
l:::l
|
:l--^

f;fr5r0

SHAF
TONSANDSTONE
_E=Ei_ors
:+---J
-l

rl----- -.'|
f- -----J

COALMEASUREST_-__-1
- - - l

t----t

) 1 , ,.|l

X'
'tl;.1

)l
9-1
iltl

{1

r>:i';l

STOT6UNITEO
AFTERTHAW

HIGH
P R E S S U R E \. *i#i;)+f+Y,l
P V . CS. E A L

#r"

..N

l',;t-'-,*
|

ftY.t '

t{

YK

w _els

Wlt.k-,,1t+l#x-i,^-

..

INSET

CONSTRUCT
I OI N TO E T A I L
JO
NOHINAL
WALL
THICKNESS
6ROU
PIPES
GRAVELRETAINEO
BEHINO
STEEL
S H E EN
T6
I
S P E I I A L6 R O U R
T I N 6O E T A I L

Flgure

3.

ShafE sectlon'

t'lth

geology and estinaEed

r.raEer ln

flows,

North

Selby

No. 2 (upcast)

shaft.

o-rifo t-"."r'

I-e

oi
ol

*i
S E C T I O NB - B

tI
S E C T I O NC - C

S E C TI O N A - A
Figure

4.

Collar

and foreshafE

struccure

with

fan drift

entry,

Selby Rical-l

No'. 2 (upcast)

shaft.

all lnposed
In addltlon
to belng able to withstand
and horizontal,
at collar
loads, both vertlcal
level,
the collar and foreshaft are designed to
resist ground and water pressures acring radlally
which lncrease with depEh. The
on the structure,
crib situated at the base of che foreshaft assists
load at this level over a
ln spreading the vertical
larger area, reducing the bearing pressure, as well
key lnto Ehe strata.
as providlng an addltional

terln shafts allow one Eo be used for air entry and

Entry and rernoval of
the second for air exhausE.
alr nay take place through the headfrane bullding,
founded at collar
l-evel, or vl.a an incl,lned drlft
with a slde entry into lhe collar and foreshaft
Flgure 6 illusErates
below ground level.
structure
for a shaft
a reinforced concrere exhaust fan drift
A slnllar
in whlch the air Ls upcast.
structure,
would be provlded for alr
lerned an air drift,
entry to the downcast shaft.

2.4 Lft

The design of air and fan drlfts

follows standard
basLc prLnclples.
Since one end is attached to a
rigld
foundaElon - the shaft - slnilar
support must
be provlded over the reoainder of the drift
lengEh.
Therefore ln all cases other rhan hard
rock plled foundatlons are necessary.

and fan drifts

ls a very inportant aspect of

Hine ventllatlon
Normally shafts are sunk
underground operatlons.
in palrs, one for rnlneral winding and the other for
access.
As a secondary function,
nen and oaterlals
8

Figure

5.

View down selby

Eo the right.

wistor./ No. 2 (upcast)

shaft

collar

and foreshaft

structure

r{ith

fan drift

entry

Design is based on the analysis of the box crosssecEion to resist surcharge loads, overburden
pressures and lateral
ground pressures together
wlth any loads fron surface structures
founded on
top of the drlft.
Section C-C of Figure 6
indlcates
that Ehe side walls of the fan drift
have
been deslgned as deep beams over Ehe sDan becween
Ehe shaft and cencral plle cap to acconmodaEe heavy
foundatlon loads fron surface struclures.

be augroented by an lnvestlgatlon
lnto the partly
constructed state of a single span with a
cantLlever sectlon over the cenEral pile cap.
The
latter
condltLon is of partlcular
importance in Ehe
case of a shaft sunk in frozen ground.
ConnecElon
of the drlft
Eo the shaft should only be made afcer
Dost of the ground settlement
durlng thawlng has
taken place.

ConsEruction sequences should be taken account of

ln deslgn.
The abllity
of the drifE to act as a
Ehree 6pan beam ln lts final
condition
nay need to

Air and fan drifts

are noE fully
underground
structures
ln the true sense, but they are of
partlcular
importance ln that Ehey forrn an
lncerface
bellreen the underground and Ehe surface

2' 930

I
I

S E C T I O NA . A

I
'ouJld

Led

I
l

IA

I
l

SECTION
B-B

t st'ofi

IA
S E C T I OC
N- C
Flgure

6.

Fan drlfE,

Selby Rlcal1

No. 2 (upcast)

shaft.

works.
As such, they are not slnple Eo construct,
requirlng
the correct
tenporary works approach,
englneering
and rnlning
conbinlng both civil
technlques. Connectlon to rhe shaft takes place at
ls poor and ground
a polnt where ground stabllity
water lngress lnto Ehe excavatlon is llkely.
Hence
every atEeDpt should be nade ln the deslgn to
sinplify
the shafE rouChing deEail and to provlde
the surface works structures wlth foundations
independent of the air and fan dri.fts.

both the shaft neck rlng and the horizontal

roadway
sections are deslgned ln accordance nl!h thelr own
princlples,
then fron experlence l-E would appear
that the lnterconneclion
between the two Eakes care
of itself.
One of the nost dlfflcult
aspects of lnset design
ls to deterolne accurately what the true loading
In nany cases rule of thunb nethods
should be.
have been enployed, based on local knowledge and
scapdard practlce in parllcular
nlnlng arees.
Figures of^13.4, 26.7 and,53.5 kN/n2 (L/8, Il4 and
l/2 ton/f.tz respectively)
were the norn untll
recently when the values have risen Eo 106.9 to
213.8 kN/n2 (l to 2 tons/ft2).
Appllcation of thls
loading has tended to be on a unlfornly
distributed
basls aI1 round, although in sone lnstaccps values
of 106.9 kN/nz (I tor./fEz ) have been taken on the
roof with 53.5 kN/n2 (L/2 tot/ft2 ) applied ro rhe
vertical
sides.
No apparent logic acconpanles thls
method of load determlnation except Ehat lf the
same intenslty
of loading has been enployed to
design another structure of this type in a sl.ollar
mining area erlthout detrinenEal effects,
the
concluslon has been that it nust be satisfact.ory.
Generally this principle
holds true lf lhe ground
is conpetent but in a rule of thunb approach the
true factor of safety ln the design renains
unknovn. Where the ground is lnconpetent, hosever,.
the chances of structural
fallure
becone verv real
when uslng thls method.

2.5 Insets
Havlng sunk and l-ined a vertlcal
shaft lt is
fron the
necessary to drlve away horlzontally
The structure
which ls constructed a! the
botton.
plt botton thaE enables this work to proceed ls the
Figure 8 is a vlew of a
lnset (see Flgure 7).
relnforced concrete lnset under constructlon.
The
functlons
of rhe lnset ln a worklng mine are to
provide sklp loadtng facllities
for production
wlnding and transfer
lnscallations
for oen and
Ic also plays an lnportant part ln the
naterials.
nine ventilation
scheee.
Deslgn prlnclples
for lnsets enconrpasstwo dlstinct
fron the vertical
approaches as transfer
directlon
is acconpllshed.
to the horizontal
Shaft Ilnlng
involves a uniforn
deslgn nornally
loading around
acting ln a radial direcEion,
the circunference,
which creates a cornpressive stress wlthout bendlng
on a clrcular
shape. With a tunnel, depending upon
the overburden pressure and the deformation
pressures nay
charecteristlcs
of the rock, lateral
fron the verEical ones and bending
be different
l o o m e n E sa n d s h e a r f o r c e s a r e l n d u c e d i n a c l r c u l a r
proflle
under Ehese circumscances.
In fact, for
the rectangular
and haunched arch profiles
shown in
Figure 7, bendlng moments and shear forces are
presen! whether the loading ls uniforn
all round or
However, Eheir nagnlEudes could change
not.
depending upon lhe ratio
bet\reen the vertlcal
and
pressures.
Despite this problen, provlded
lateral

For good design, therefore, 1t ls inperatlve to

have a more reaListic
approach to the evaluation of
the inset loading.
In this respect, partlcularly
with the siEing of structures
in coal neasures
strata,
the work carried out by the NCB Minlng
Research and Development EsEabllshnent. at Brecby ln
England has been helpful 3.
Ustng [.lllson's metiod
of design, the closure of an underground drlvage in
weak rock can be related co the linlng
strength and
the rock properties
obtained frorn laboratory
tests.
In this way, a llnlng
can be provlded whlch

P o c k e t sf o r s t e e I b e o n s

SECTniB.B
Figure 7.
IO

Shaft boEton inset,

Selby hristow No. 2 (upcast)

shaft.

wi.ch the surrounding strata,

and sith
ls conpatible
It should be noted,
a knorm factor
of aafety.
however, that sitlng
of an lnseE relatlve
to the
coal seam ls of partLcular
lnportance
and
preference should be glven to locaELons above and
belos the softer
rocks assoclated with rhe mLneral
body.
once the true lnset loading ls established,
it ls a
relatively
sinple natter
to determlne the bendlng
nonent6 and shear forces for typical
cro6s-sectlons
such as SecElons A-A and B-B shoun ln Figure 7.
The use of a conputer,
for which standard
prograns are available,
structural
engineering
nakes Ehe analysls
In the analysls of the
easler.
sEructurer account musE be taken of Ehe resistance
to deflexion
of the surrounding rock.
The correct
propertLes of the ground need to be
defornatlon
introduced
into Ehe program as sprlng sciffnesses,
as the surrounding
rock rnodlfies the bending
monents and shear forces that rrould occur lf Ehe
strucEure were to be considered as unconfined.

2.6 Tunnels
Baslc principles
for tunnel lining
design have been
touched on briefly
in the previous section on
inseEs.
This is not surprising as the horlzonEal
section of an lnset ls sinply a Eunnel.
The added
conplicatlon
in Ehe case of the inset ls the
inEerconnection wlth the shaft.
As with Ehe inset,
the 'secrett of good tunnel linlng design is to
provide a system shich is conpatible
wiEh the
surrounding ground.
This means natching up the
defornatlon
characEerlstics
of the ground and the
lining.
To ful!,y understand Ehe role of concrete in tunnel
llning design, it is necessary to be fanillar
wlth
tunnel deslgn and construction
techniques in
general.
Lining requlrements
for tunnels vary
immensely depending upon the ground conditions.
Tunnels in hard rock nay be conpletely
unsupporEed

Figure

8.

WisEow No. 1 (downcast)

shaft

boEtorn inset

'cosmeElcr llnlng.
erith no addltional
In other
types of straBa, rock boltlng uay be sufficlent
to
provide permanent scabllity
to Ehe excavatlon rrl-th
the posslble use of nesh and sprayed concrete 10
zones to prevent fragnents
from
more friable
falling
off or surface weaEherlng.
pernanent support nay
For weaker ground condltlons,
be achleved using arches, beams and columns or
complete rings, all fabrlcated
fron standard 6teel
sections.
.Alternatively
spheroldal graphiEe, cast
st.eel segments or precast concrece segnenEs provlde
a convenienE form of circular
Eunnel construction,
partlcularly
close -to the
ln sofE ground condltlons
be
aurface.
Cast steel segnenEs would noroally
enployed as the flnlshed
linlng
because of their
hlgh load carrylng
capacity,
but the other
steelwork support sysEerls and the precast concrete
segnents nay also be used as temporary works prlor
to lining
ln concrete on a more pentranenE basis.
Flgure 9 shows a typlcal
soft ground cunnel
construcElon
ln which precast concreCe units were
installed
as temporary support prlor
wlrh
to lining
ln slEu concrete.
Flgure 10 ls a photograph taken
lnside one of the tunnels.
As for lnsets,
accuraCe deEernlnation
of the
lnposed loadlng ls of fundanental
lnportance
ln the
deslgn of tunnel llnlngs.
Hany soil and rock
nechanlcs theorles
are avallable
Eo deternine
pressures on tunnels ln various ground
q.
condltions
Two baslc types of loading
predoninate.
One consists
of a triangular
shaped
zone of roof strata whlch is consldered Co break
away under graviEy to Lnpose loading on the
supportlng
structure.
This could occur in
sEratlfLed rock of a conpetent naEure with no side
or floor loading present.
The second prlnclple,
used in neaker ground, considers a yield zone to
exlst around the opening J.
This occurs because
Ehe strengEh of the rock is lncapable of
wichsEandlng the high locallsed
sBresses r,rhich are
created around the perlneter
once the excavation
has Eaken pIace.
Initial
yielding
fl:rst rakes

under construcEion.
11

aurtr Nlax
SIru6Uft\

- - -rilY

ntlfi

ruraoE
$^f IS

l","a"
r*^r*
ttlsrtxcl

I @cRur
66 oar ar

.?00

lgrc

tr

GRO LEYL .O 5' APruX

oiooi

cuY

MffiTO

s-tur|e

IE'P

SCTIONOF TUNNLS (2TSI

LO^IGITUOINAL

Eolt0 PRc^5r
coNcREr *GXrrs
tEVt
-J I E L S --$if

V 4 .tfS Fe@ -tl @ b'(!

-\a'

T Y P I C A LC R o S SS E C l l o N 0 F T U N N E L S1 2 N o l

Flgure

9.

Soft

ground tunnel

const.ruction;

one of

two coollng

place at the excavatLon face and graduelly

spreads
further
lnto the grouod untll
stablllty
is once
The opening ls therefore
agaln restored.
conpletely
rlnged by a partly
zone.
crushed (yleld)

water

lntake

tunnels

at

Grain

Polrer StaElon.

excavatl-on, shlch ls restral.ned at the drlvage

face, Lncreases t lth distance back fron the face up
to approxlnately
flve to six dianeters shen at chis
posltlon
lt ls Eostly conplete 3.
Sone rocks,
however, such as salr,
exhlbit
tloe dependent
moveEents whlch nay contLnue throughout the tunnel
11fe.

In both these approachee, the tLme since excavation

fron the excavatlon
and the dlstance
face are
crlclcal.
An unsupported roof, shlch is coopetenc
shen excavated, nay becone unstable with cioe as
defornatlon
takes place and larger gravity
forces
are brought lnCo play ln conJunctlon wiCh the
Lncreased trlangular
loadlng.
Closure of an

Based on the prevlous commencs, lE can be seld thac

the rart' of tunnelllng
consiscs of installlng
the
(safe, econooLcal and serviceable)
most su{table
llnlng
at exactly
the rlghc tloe ln phase with Ehe

Figure

water

t2

10.

The inside

of

the Grain

Power ScaElon cooling

intake

tunnels.

\\v

it

,<\\v

-\\v

,\\v/

?,<\\v,7<\\v7l<\\

7 315 Dioknrtcr

- --/ ||
()

tI
[\

C A S TB A S A L TT I L E L I N I N 6

.n,,.
l,"n
I

II
I

-,--

S E C T I O NB - 8

Flgure

ll.

Typlcal

1000 tonne spiral

chuEe bunker

shaft.

proceedlng excavatlon.
The bull.d up of load for a
rgof zone approach ls a progressive
one
trlangular
due to the gradual loosenLng of the rock ln the
Restrlction
roof dependent upon tiDe.
of roof
deforoatlon by lnnedlate lnstallatlon
of the lining
prevents the zone of influence
fron spreadlng and
nLnlnizes gravlty
forces.
In the caae of a yleld
zone, lmmedlate lnstallatlon
of support close to
the drlvage face could be achleved but lEs requlred
6trength sould be excessive.
InsEallatlon
of the
llnlng
at some dlstance back froo the face needs
less support a6 part of the closure has already
Provlded the ground renalns cotopetent
taken p1ace.
(eelf standlng),
then the re-adJusted stresses wl11
be carried
by the 8lrata
or wlth the asslstance of
ninlnal
tenporary support prlor to lining
wlth a
thln skln of structural
concrete.
The technlque of allowlng
the rock ltself
to carry
ae much of che poat excavatlon atress as posslble,
ln conJunctlon slth a ninlnal
llnlng,
nay be
considered to be another rsecretr of good tunnel
deslgn.
The Nev Auscrlan Tunnel Method (NATM) 5
deEonstrates
thls aspecB to the full
and enploys
nesh and a thln skin of sprayed
only rock bolts,
concrete as Che prluary
support sysCeo which
the ground to carry the load.
asslsts
Ic ls lrlthin
thls context that concrete ls used ln
tunnel construcClon.
The ground conditlons
and its
defornatlon characterlstics
subsequent Eo excavatlon
nust be knorn before lining
concepts can be fully
Pre-knowledge of ground condlcions
fornulated.
ls
hydrogeologlcal
obEalned fron geological.and
borehole
T h e N A T Mg o e s e v e n f u r t h e r
data.
ln lts lnpllclt
and ln sLcu observatlons
rellance
on lnstrunentation
proceeds.
These observatlons
as tunnel constructlon
are used not only to checkr'on the perfornance and
safecy of the tunnel but to'gulde the provlsion of
supPort.
secondary or tertlary
Ic can be seen that. the possible range of concrete
usage for tunnel construction
wide and
ls therefore
enbraces the full
range of sprayed, precast and in
sLtu work.
The use of sprayed concrete is
nldespread underground and nany references are
avallable elsewhere concernlng iEs use.

2.7 Spiral

chute bunker shafts

The concrete structures

discussed so far have al1
been related
to verBlcal
shafEs or horizontal
We now coDe to varlous structures
tunnel drlvage.
whlch are consCructed to fulfll
speciflc
functlons
connected wlth working olne operatlons.
In a mlne, handling faclllties
underground are of
exEreme lmportance for transportlng
the exlracted

Flgure
L4

12.

CeurentaEion Mining/Buchan

bolted,

precast

naterlalto the surface.

Coal is nornally
face to the
transporced underground froB extraction
holsclng shaft, or alternatlvely
to the surface up
using conveyors. The current
an lncllned drlft,
trend ln coal Elnes ln the United Kingdom,
following
thelr original
developrnent ln Gernany, L6
to use splral
chute bunker shafts (see Flgure 11)
These provlde
loline
on the conveyor sysEen.
to belng
underground ln addltlon
storage faclllties
Coal is fed lnto
a means of regulating
coal flov.
the inlet
chute, sltuated
ln che bunker top
ln the chute
chauber, and flows downwards splra1ly
set into the val1.
The purpose of the splral,
as
opposed to a free fal1 systen, ls to control the
inflow of coal so that degradaclon and the riak of
lncendive sparklng are reduced and wear on the
Rernoval of coal
shaft rralls and dust are miniuized.
is through Ehe conical outlet
in the bottdu chanber
roof,
feedlng back onto the naln 1lne conveyor
The bunker shaft shown ln
transportatlon
systen.
Flgure 1l ls construcEed from relnforced concrete,
cast in situ.
At the present tlne,
splral
chute bunker shafts are
construcred wlth a dlaneter of 7.315 n (24fC) and
nlEh a helght nornally
of about 40 o Eo glve a
capaclty shen full
of 1000 tonnes.
Constructlon
of spiral
chute bunker shafts can Eake
several forns.
They nay be installed
uslng snall
precast concrete blocks (Thyssen systeo) or larger,
bolEed, precast concrete shaft linlng segnents
(Cenentatlon l,tlnlng/Buchan systetr).
In both cases,
(see
special unit.s are requlred for the splral
Figure 12).
Void filling
behlnd these unlts durlng
lnstallatlon
is carried out uslng a groutlng
process.
Alternatlvely,
in sltu concrete can be
used with or wlthout glass fl.bre relnforced
concrete panels as permanen! fornwork.
In all
these foros of construction,
cast basalt t1les
provlde the wearing surface for the splral proflle
(see Flgure 1l).
Deslgn prlnciples
for the infeed chute to the
bunker top, the spiral
ltself
and the outfeed
systen, are outllned by voss 5,
In the structural
deslgn of the shaft, the question of loading is
forenost:
two kinds require scrutlny.
Flrst,
the
contained material imposes silo-type,
lateral
pressures and vertical
shear forces on Che wall.
Second, the possiblllty
of external ground loading
must be considered.
However, in nost cases,
ln cotrpeEent ground and
bunker shafts are situated
wlll
only be subjecced to external ground pressures
tf
further adjacent development drivage is carrled
If this occurs, ground novenents
out
subsequently.
inpossible to deflne
could be large, virtually
accuraeely and cannot be accomuodated ln deslgn.

concrete,

splral

chute bunker

shafE segnenE.

In conpetent ground, the load of Che coal contalned

ln the bunker can be transferred directly
from the
lining
to the surrounding ground by mechanical
interlock.
Lateral pressures are resisted directly
by the rock, and vertlcal
shear forces by
frlctlonal
reslstance
and nechanical
interlock.
Lialngs of bolted precast concrete segments, ln
sltu concrete or flbre
reinforced
concrete panel
tlipes therefore
need only be designed nonlnally
for
strength as the internal
loadl-ng is dlsslpated

into the ground.

dlrectly
Thls leaves the baee slab
and botton chanber structure
to carry the effectlve
vertlcal
silo pressure aC that level.
The spiral
chuce also servea to lmprove the interaction
between
the bunker and the ground, providlng
an exEernal
corkscrew effec!.
In fhe case of the block lining
however, in whlch Che elenenEs are noc physlcalty
connected together, consideratlon
may need to be glven
to carrylng
Ehe fu11 welght of the 6haft lining
and
Ehe bunker contentE on the botton charnber structure.

sEcTtott
c-c

Floor rlob pruturt

ond grouling pip.l

rrlirf

sEcTr0N
8 -8

Figure

13.

sunp Eank for

holdlng

mine water

prior

to

pumping Eo surface.
l-5

stroro c

c$cr

:o

groriag clil

rctr

ll
tl

V I E WO N B - B

Flgure

14,

Underground safety

plug

and bulkhead

2 . 8 S u m pt a n k s
The control of eater ls an lmporEant aspect of
operatlng
an underground nine. Sunp tanks are
required Eo act as collectlng
points for
lnvarlably
water.
Punplng arrangenents can then be eoployed
for iEs transfer to other parts of lhe Dlne or to
the surface for disposal.
A typical
reinforced
concrete sump tank is
illustrared
ln Flgure 13.
This Eank has been
sltuated in an area where ingress of wacer could
occur through the strata behlnd the side walls and
Hence, a pressure relleving
below the floor.
systen has been lnstalled.
The pressure rellevlng
systen consLsts of a number of plpes leading out
frorn below the floor
slab to prevent bulld up of
sErata water pressure which could danage the
These plpes could also be used Eo grout
strucEure.
up the inEerface zones for seallng purposes lf lt
were necessary to flll
the whole area conpleEely
nlth concrete due ro excess water ingress.

door.
naterlals,
equlpoent and servlces to pass through
and also be capable of rapid closlng off.
Such a
plug, lncorporatlng
a bulkhead door, ls shown ln
Flgure 14.
The plug which is illustrated
has been designed on
pressure could
the basis that full hydrostatic
prevaLl ln the event of a flood,
the naxinun head
belng the depth fron Ehe ground surface to the
lnsEallatlon
level underground.
Three naln
elements are incorporated in the plug:
(a)
(b)
(c)

plug;
concreEe cyllndrical
steel load transfer cylinder;
steel bulkhead door.

2.9 Plugs

plug has two purposes. T'tle

The concrete cyllndrlcal
flrst
is to provlde a barrler to wlthstand the end
pressure.
This ls achleved by
hydrostatic
provlding a sufficient
length to keep the shear at
withln pernlssible
the concrete to rock lnterface
llnlts.
Secondly, the plug is deslgned as a oeans
the passage of nater through the plug
of preventlng
ltself,
aE the concrete to rock lnterface and also
chrough the sErata. When groutlng the contact zone
between Ehe plug and the rock, or grouting
the
greater pressure than the prevailing
6trata,
head
ls requlred,
to chase the water back along its
paths.
lnflow
The concrete tube nust therefore
be
capable of wlthstanding pressures marglnally ln
excess of hydrosta!ic
in the radlal direcEion.
AddlClonal grout seale help to close off possible
leakage paths.

Allled
to the cootrol
of eraEer in a mlne is the
abllity
!o seal off secEions against naJor
lngress.
Plugs may be lncluded for safety, as mine
developrnent proceeds, or they oay be lnstalled
as
an emergency procedure if a large lnrush occurs.
The foro of the plug varies depending upon the
condltlons.
In an energency, a solld concrete plug
would be constructed
as a permanent sealing off
tDeaaure. Plugs lnstalled
durlng an Lnltlal
nine
developnent scheme will
need to a11ow men,

The steel load transfer

cyllnder
bears onto rlng
flanges and allons
che bulkhead door pressure Eo be
plug.
carrled by the concrete cyllndrlcal
Enough
flenges are provided to reduce the bearing stresses
to pernlsslble
llolts.
The steel bulkhead door is
deslgned to carry the full hydrostatic
pressure aod
also lncorporates a man access tube.
Servlces can
b e c a r r L e d t h r o u g h s t e e l p i p e s e r n b e d d e di n t h e
plug, glands belng lnstalled
concrete cyllndrlcal
at both ends of the plpes for sater sealing.

In some areas underground, the sErata condltions

nay be sufflclently
conpetent and lnperrneable Eo
al1ow water storage without any addltlonal
lining.
A thin layer of sprayed concrete on steel
nesh may sufflce ln oEher areas.
However, where a
nore substantial
sEructure ls requlred, the design
should follow the guldellnes of Lhe relevant Code
of Practlce /.

r6

5. Gonstrrrction Method.s
3.1 Introduction
The use of concrete ln underground developrnent work
FlrsE, any excavatlon
has three dlstlnct
aspects.
nust be secured before casElng the concrete against
This lnvolves provlding the correct tenporary
lt.
uorks support ln phaee wlth the excavatlon
procedure.
Second, fornwork and falsework are
when placed,
requLred, to ensure thaL the concrete,
remains ln the desired positlon
and ls of the shape
expected.
The thlrd
aspect of concrete
construction
ls the ablllty
to roove the fornwork
for subsequent
and falsework safely and quickly
pours.
In Ehe following secElon6, these aspects are
consLdered with reference to the partlcular
prevlously descrlbed.
struclures
Subsequent
secELons cover batchlng planc and transportatlon
and placing technlques.

for the excavatlon consists of steel llner plates

fron
being fabrlcated
and steel rlngs, the latter
Thls lype of teEporary support
standard sections.
would normally be used through the soft,
surface
On furrher
soil deposlts untll
bedrock is reached.
slnklng
ln competent ground, only rock bolts and
mesh need to be used for tenporary support.
In frozen ground, the strengEh of the soft surface
soll deposits Ls enhanced to such an extenc that lt
renalns competen! when excavated.
The 1lner plafes
and rings are provided, therefore,
as an addltional
safety neasure and also to prevent squeeze on the
freshly cast concrete llnlng as a result of thdwlng
ln the ground caused by heat of hydratlon
However, care nust be Eaken to ensure
developnent.
that the ice wa1l is conpletely closed around its
perineter,
below the freeze cellar,
in order Eo
prevent Lngress of ground water Lnto the
excavat lon.
Where the ground freezlng
nethod i.s noE used,
conslderatlon
oust be given to providing
teuporary
supporE which can sustain the inposed ground
pressures.
A dewatering scheme could also be
needed.

3.2 Collars and foreshafts

Figure 15 illustrates
lhe method employed to
construct the collar and foreshafE of a frozen
shaft and Flgure 16 ls a vlew looking inslde at the
teoporary support provlded for such a scructure,
prlor to lining ln concrete.
Th tenporary support

The llnlng
forowork and oeans of handling the
concrete in the collar
and foreshaft are sinilar
to
the equivalent itens ln standard shafE slnklng
practlce.
They are detailed later in Section 3.4.

Tl pDlng

Fopo

8rnktrnana
V.ntll.tlon

Crbin

Frn

Acca rl
Ladatariay

Tonporrry Support
llnel
TYPICAL

FORESHAFT

coxsTRU
cTtox

Tamporary Srttort
Plrt.!

Hoppit

Trrcl lountad
!.ckho.

Figure

15.

Col-lar and foreshafE

excavation

and

tenporary

support.

L7

Figure

16.

Wistow No. 2 (upcast)

shaft

collar

and

3.3 Air and fan drifts

Provlding
a tenporary works schene for air and fan
problens.
drlfts
has its own partlcular
As
Dentloned ln Section 2.4, connectlon to the shaft
polnt for ground
Eakes place at the most vulnerable
stablllty
and ground nater ingress lnto the
At this point,
excavaElon.
the tenporary works
scheme for the shaft construcllon
must be Eatched
up lrith that for the drlft.
In addition,
in frozen
ground, the freeze cellar
muat be supported above
this posltlon rhile
excavation proceeds belov (see
Flgure I7).
In conjunctlon
slth a ftozen shaft,
a frozen ground
tenporary works support systen for the drlft
can be
provlded. However, thls is susceptlble to severe
ground novements ln the forru of heave durlng
freezlng
and seEtlenent ln the thasing perlod.
Provided the ground condltions
are sultable,
the
aulhorrs preferred DeEhod of tenporary works Ls the
folloving.
(l)

Provide sceel sheet plles for the drlft

right
through to the proposed shaft collar
excavation
perineter,
prior to lnstalling
the shaft freeze
tube dril1 pad and the freeze cellar.

(2) Durlng the freeze cellar constructiont

excavate
below the floor slab to provlde
reinforced
concrete corbels whlch could Iater become an
part of the shaft,
integral
reinforced
concrete
collar strucEure.
Care should be taken not to
excavate deeper chan the top level of the proposed
drlft
Provide enough corbels !o carry
roof slab.
the weight of the secElon of freeze cellar
spannlng across the drift.
Provide relnforcement
at the rear of Che corbel for bending outwards,
on exposure durlng the shaft excavatlon, to provlde
the necessary tle ln wlth the shaft collar.
The
freeze cellar struccure ltself,
should be a
relnforced concrete strucEure capable of belng
carried by the corbels over the widEh of the
drift
excavatlon.
l8

foreshafc

under construction.

Providing sheet plles rlght through to che shaft

wall ensures that the ground 1s coropl-etely secured
while the freeze cel.lar ls
at Ehis posirion,
Where ground
supported from the collar structure.
water ls present, a well dewatering syslem oay be
required.
In Section 2,4, IE was reconmended that connectlon
of the drlft
to the shaft should not occur, in the
case of a frozen shaft, untll
thawlng setElenent ls
Provislon nust be oade, therefore,
conplete.
during constructlon
for thls to be accommodated.
Gaps, wlEh or nlthout contlnuity of relnforceruent,
oust be allowed in the floor,
walls and roof for
this purpose.
Where the reinforcenent
is ninlmal,
a 300 nur gap with continuity
would probably
sufflce.
For an abundance of relnforceuent
ln the
deep bean side walls of the box cross-sectlon
drlft
(see Sectlon C-C tn Figure 6), rehich provldes a
nuch stLffer
eleoent of realstance
to bendlng, a
wlder gap preferably
of at least a required
lap
length, should be allowed with dlsconllnulty
of the
The detail
steel.
r[ust also be watertight
and
requlres a steel seallng plaEe across the back of
the gap.
Fron Ehe posltioning
poln! of vLes, the
best locatlon
is away fron the shaft towarde che
centre plle cap.
Proprietary
formwork systens can be eoployed for
the constructlon
of alr and fan drlft,s wlth tregtles
for roof sofflt
support.
ConcreEing proce<lures are
sinllar
to those used in surface works.

3.4 Shaft llnlng

Flgure 17 lllustrates
the basic elenents lnvolved
ln the lining of shafts.
Lining 16 carried out
downwards, as sinkLng proceeds.
The face of the
excavatLon ls only advanced as far ahead of the
llnlng
as the ground condlElons allow,
the sldes
belng secured by rock bolts and nesh.
In wet
condltlons
backsheet.s of PVC, fastened to the rock
bolts and oesh for castlng the concreEe agalnst,
are used to channel the wacer behind, outflow belng

Sinking
heodfrome

Mucking
system

Brinernqin
F r e ez e c e l t o r

4 Orum
c o p s t o nw i n c h

Ventilotion

Doubld
erum
wi nder

Air drift
ond shqft cotlqr
F r e e z et u b e s
S c r v ci es

H o n g i n gr o d s
for formwork

Pumping
ryrtrm

M u t t i - d e cskc o f f o t d
S t o n d q r df o r m w o r k

M u ck i n g
unit

M u c kh o p p i t

Figure

17.

Coumencement of

shaft

sinklng

C q c t u sg r o b

and

llnlng.

t9

Vcntilation

Derh Pol

Riring

Protrct i vr

Mrin

Canopy
Blatt ing Bor
Stcady Cheinr
Concrrt c

Guidc Rollrrr

D ir t r i b u t i o n

Shuttrring

Shuttrring
Winchrt

Hrnging Rodr
Switchgrrr

&

Communicet ion

Lighting

Crblr

Trrnsforrnrrr

Concrct ing
Pipr

Boo t

Signi I Cablc
-\-Wrtor Tank

TooI 8or
Strgr
Stegc Lighting

Pump

Vcnl ilat ion

Jacks

Wete r

Stcady
Opcning Covc r

Sinking

Light r

Tool Box

Drivcrc

Cab

Rotary Arm
Muck ing
Unit

Cactug Grab

Sump
Pump

Hoppits

Figure 18.
20

Scaffold

used for

shaft

slnking

and llning.

concrolled vla pipes

fornwork for punping
polnts.

to the grout ports ln the

to the surface dlsposal

seatlng upon whlch to loirer the complete eet of

formwork rlngs fron the prevloue pour.
The
lowerlng of the forosork
ls achLeved by rneana of
wlnches sliuated on lhe scaffold (see Flgure 18).

A11 slnking,
llnlng
and fornwork handllng
operatlons ln a shaft are carried out from a nultldeck scaffold suspended fron the headfrane (see
Ftgure 17).
A capst.an winch ralses and lowerg Ehe
ecaffold.
Flgure 18 shows the general arrangeoent
of a typlcal
scaffold and Flgure 19 ls a view of a
four deck scaffold belng installed
ln a shaft..

Flgure 2l illustrate6
the concrete llnlng
Pour doors in the fonnwork asslst lJlth
sequence.
the placlng of the concrete and the speclal shaped
Jolnt (see Figure 20) pernlEs natchlng up to the
prevlous pour.
The concrete 1s tran6ported
fron
plpellne ln the ehaft,
the surface, via a vertlcal
and ls received first
by a dash pot and then by a
dlstrlbutlon
box (see Ftgure 21).
Passage into the
fornwork ls by oeans of flexible
hoses attached to
eteel ptpe outlets
from the dlstrlbution
box.
}{ethods of concrete distributlon
are dlscussed nore
ful1y later ln Sectlon 3.10.

Shaft linlng
formsork (see Flgure 20) is supported,
during concrete pouring,
by rneans of hanglng rods
suspended fron the llft
above.
The kerb ring, once
it ls llned and levelled,
acts as a scop-end co the
boEton of the llft
belng consEructed and provldea a

Figure

19.

WlsEow No. 2 (upcasE) shaft

four-deck

sinking

scaffold

being installed.

2l

ProvlourlyConcrctrd
L.ngth

Groutrr Rlng

Rt x o s

Hrnglng Rod

Irtch.r

Rlng

Strndrrd Rlngr

Rock Soltr

Groutlng Portr

Wlro Iorh
Prnrlr

Concrrtr PourDoorr

S t e n d r r d R l n gr

Hrng Ing Rodr

tcrlblng
lor rd r

Krrb Rlng

HrngIng Rod llutr

Figure 20.
22

Shaft

fornwork

rings.

+i D^__A
+i
r.h

- tEcoxD

-I!!!L

i' eorr''

-{--"-.".--+?,

Ierl
llil
torr

!l-i'l

?o9
O.cl

llel
I
A Oorn
I

tlnt r aCD
Pou ? l l

l-

Loneth
L..l
Of Concrata

llrjr
F O
I ll Drrr
Porr ltl

rE Dorn

L-

ar.
Drc I

J$.P-_

Concrala
Pl.canrit

\
Flllrr 1
nlnl

Concrolo
Placailant

Fron

\
\

ln

fDlcl

<
I

ilrrr I o
\
\f

t..
g.cl

Go n c rl t o
tlacariant

2..

D.CI

Fron
JEtcr
D.CI

X.rl

L.nath

Ol Hrallng
Ircllne
U n lt

Pour | |

co]acnETE L|lilltc sEouE]tcE

SHAFT SECTIO}I

iodr

Pour I | |

3.5 Insets
requires partlcular
In6et constructlon
mlnlng
expertise.
Concrete pour slzes must be closely
related to the excavatlon sequence. Flgure 23
6hou6 the stages ln the constructlon
of a typlcal
lnset slth numbers ln clrcles
indicatinq
che
aequence.
Inmedlately before excavatlon comences for the
inset, the shaft llnlng
is secured do!.n to a
euitable level innedlately
above. Noroally
reinforcement would be provlded wlthin the shaft
wall, ln the secclon adJacent to the inset, to

Figure 22.

24

trristow No. I (downcast) shaft

and excavation below.

create a neck rlng for Ehe purpose of securemenE

movement
and to provlde reslstance to dlfferenrlal
Once the rlng has
between the shaft and the lnset.
been constructed, excavatlon can proceed downwards
ln soall stages wlth headlngs belng driven
transversely uslng steel arch tenporary supports.
A speclal technlque used ln inset consCruction is
the provLslon of a haunched arch roof (see Figure
22).
In addltlon to reduclng the bendlng moment on
the roof slab, by means of the arch, the haunchlng
allows it to be casE and'lockedr
in to the ground,
and subsequent excavatlon can proceed below wlthout
a n y o t h e r r n e a n so f s u p p o r t ( s e e F l g u r e 2 3 ) .

inseE under consfrucIion

sliowing suspended haunched arch roof

o
N

ARRAXOEIEXT OF PIT EOTTOH INSET

@

P o c k e t sf o r s t e e t b e q m s

C o n s t r u c t i osne o U e n cneu m b e r s

n
r

rI - - {
a

ol

(ot
01
el

P1
d

ol
.'i
ct

ut

"1
1

f--

z
N

o|I
@l
FI
r?l

i
!)
q
n
@
0,

|I

1.t32O

__
23000

ti - - - - ^

rr

-ll
-r*-

I'

, _

+lL1 O 6 6 s _
-_

|
23000

M e s ho v e rq r c h e s
o n d t i m b e rp o c k i n g
t o e x c o v o i i oI ni n e

8 f t t o n gr o c k b o l t s
1

i
I

H y r i bs h u t t i e r
rete infitt
I o n c r e t ef t o o f R o d

Ercavation
tamporrr y
conrolidat.

for and instellation of

supports compl.t.d.
sid.s with concr.t6.

E XCAVATION OF
N

B o c k f i tst h u t t e r
left intqctqnd
e xt e n de d

B q c k f i tot f s t e e p e r s
ond Lytog

Roof and hauncha3 pour complctod.

Support shuttars 3trippcd.

INSET

Ccntr. portion
b.nchad out to tar
cndr of inaat. Erpoard ground
bolt.d
lnd mcahod orpnd gunltod,
d.pcnding on conditiont.

Flgure 25 ts a
and noved separately.
collapsed
ln the
vlew lnside the shutters wlch the Eravellers
Concrete ls poured lnEo the shutters
background.
The left-hand
through portholes (see Flgure 26).
door provided for
photograph shows the gulllotlne
ln the roof shutEer and che rlght-hand
the portholes
one ls a vlew of the ptpe plug for pushing into the
uouthlng of the portholes ln the botton shuEEer.
Belos Ehe pipe plug can be seen an exEernal

3.6 Tunnels
nork over
involves repetitive
Tunnel conatrucElon
Rapld handling and novement of rhe
long dlstances.
Such a systen ls detailed
ls essentlal.
shulrerlng
The sEeel shutter ls specially
in Flgure 24.
in tso pieces, one for the lnverE and
fabrtcaced
Four lengths are provided
Ehe other for Bhe roof.
rleap frogging'
Uslng the
to take place.
to enable
the inverE and roof shutters can be
travellers,

vlbraEor.

S L I C KP I P E

IDEPIN--

ROOF
SHUTTER

ROOFSHUTTER
A P S ED
COLL

P0stl0N

TiIrc
MOVING
R U N N I NOGN
R AL
IS

I N V E RSTH U T T E R
-J

"tP(

I N V E R TS H U i I T E R
c 0 L L A P S E lDP o s l "T-l 0 N

4t?q!!A

L I F ING CHAIN

Figure

26

24,

R E T A I N I NW
GI R E
I N V E R TT R A V E L L E R

The Stelno

tunnel
inEake Eunnels.

moving

shutter

MOVING
FRAME

and Eravellers

MAINTRAVELLER

used

in

the

Grain

Power SEat.ion cooling

water

Ehe Grain

Power SEation cooling

wat.er intake

Figure

25.

View inside

tunnel

shutter.

Figure

26.

Ieft:a concrete guillotine

door. Right: pipe plug (top) and external vibrator
Part of the shuEter for Grain Power SEaEion cooling water intake tunnels.

(botron).

27

3.7 Spiral

chute bunker shafts

Construction nethods for spiral chute bunker shafts

elsewhere 8,9.
are set ouE in detall
The top and
are established
flrst
and a
botton chanbers
p11ot hole is drilled
and reamed out from
central
Alr and debris
the top chanber to the bottom on.
through the piloc hole as the shaft
can then travel
ls excavated downwards to lts requlred dlameter,
uslng rock bolts and nesh or boards and steel rLngs
ConstrucEion
as temporary support for the sLdes.
systems descrlbed in Section
of the various lining
2.7 Ls usually carried
out from the base uperards
excepE for the bolEed precast concrete segments.
Thls systeo has a particular
advanEage in Ehat it
as Ehe slnking proceeds
can be installed
downwards. No tenporary suppor! ls required as the
shaft ls secured ln its final
state as work
progresses and there ls no tine losE on securlng
Ehe shaft prlor to lining.

3.8 Sunp tanks and plugs

3.9 Batchlng plant

In any concrete consEructlon
work it. is necessary
to have the right
batchlng plant,
geared to the
deoand.
This is particularly
l-nportant for
underground constructLon
where pours must be
conpleted nith nininun lnterference
froo external
fact.ors.
Rates of pouring are governed by the
physlcal restrlctions
ln particular
areas
underground and by the probleo of access for
rnaterlals to those areas.

Flgure
28

27.

bacching plant ls preferred

because
and cement weighlng, and Ehe netering

The Trumix batchlng

3.10 Transportatlon and placing

The batchlng plant rnust be conveniently
sltuaEed to
the point of access to the underground fuorks.
For
shaft constructlon,
and access to underground works
via a shaft., the order of preference for sltlng
the
baEchlng plant is as follows:
:
t
(I) Adjacent to Ehe shaft top for dlrect
plpellne (for a
discharge lnto the vertical
plant supplying nore than one shaft at a
tlne this nethod would not be convenient);
(2)

For sump tanks, normal surface works formwork and

procedures are adopEed, care being taken
concretlng
pour slzes to conErol early thernal
to ninlnlze
conEractLon cracklng.
The fornwork for a plug will
posslbly on slnilar
be speclally
fabrlcated,
llnes
to a tunnel shutter \rlEh invert
and roof
sectlons.
Partlcular
attention
should be paid to
achlevlng effective
concrete placing up to the rock
overhead at crown leve1. Thl-s also applles to
lnseE, haunched roof and tunnel construcEion.
The
nethod for deallng strh [his ls descrlbed in
Sectlon 3.10.

A surface
aggregate

addltion
of water and admixtures can be controlled
Hoseverr such a
manner.
ln the rnost effecclve
sysEem depends on belng able to cran6port Ehe Premlxed concrete undergound and, in sorne
circumsEances, an underground batchlng plant nay be
This does not relleve
the problen of
necessary.
havlng to transport the concrete nix consEltuents
underground as separaCe ltems.

plant

at

and

Selby Riccall

At sone disEance fron the shaft buE nith

direct
transportatlon
to Ehe shaft cop, e.g.
plpellne
through whlch concrete ls pumped;

(3) At sone distance from Ehe shaft but wtth

indlrect
transportatlon
to the shaft top
e.g. rotating drum trucks.
Location wlll obvlously be dictaEed by site
conditions.
Where access to underground ls via a
drift,
the batching plant could be located close to
the enErance for direcE punping of concrete to Ehe
work.
Current trends on 1arge, new nlne contracCs favour
the enploynent of establlshed
ready-olxed concrete
suppliers
to set up batching plants on sit.e.
By
adopting recognised suppllers,
approved by the
British
Ready Mixed Concrete Associatlon
( B R M C A )r u ' r r o r B r i t i s h A g g r e g a t e C o n s t r u c E i o n
(BACMI) iz, high quality
Materials Industrles
control
is achieved Ehrough the utilizatlon
of
their speciallst
expertise in the productlon of
concrete.
measures for the use of
Quality conlrol
concrete underground are the same as those for
surface works and are in accordance wlth the
relevanc Code of Practice I3.
Independent approved
l4
organlsation"
nornally
employed for cube
"r.

mine.

testing, or any other tesEing of the hardened

concrete which is required.
Figure 27 shows a typical ready-mixed concrete
plant set up on slte, at the surface, and
positioned conveniently to supply the adjacent
shaft.
All operations are confrolled
by one
batching operacor.
The aggregates are stored on a
hard surface 1n separate compartments, partitioned
off with timber sleepers.
The aggregates are fed
in to the loadlng hopper (foreground) by shovel
loader.
Transfer from the loading hopper to the
173 tonne capacity,
four-compartment aggregate
storage bunker in the Econobatch set-up is by
conveyor.
Weighing takes place below the bunker
for transfer,
again by conveyor, to the 1.5 m3 pan
mixer.
A 61 tonne capacity, tHo-conpartment cement
silo is adjacent to the bunker, cement being fed to
the mixer by a screw-conveyor,
The system has a
raEed output of 45 nr/hr.
Transport to the shaft
top is by rotating drum tracks.
In establishing
baEching p1ant, it is imporEant that the weighing
equipment can operate independently
of the mixer so
Ehat nixlng
tlme becomes the only critical
operating factor.

3.f0.1 Transportation down shafts

As lndicated
earlier
ln relatLon to the
construction
of shafts, collars and foreshafts,
concrete is dropped vertlcally
frorn Ehe surface
through a 150 or 200 m lnternal
diarneter
pipeline.
To ninimize wear and to avoid blockages,
the pipe is speclally
fabrlcaEed wlth bolted
flanges Eo avold differences
in alignment of the
internal
periDeter at the jolnts.
Fixing in the
shaft is critical
and every care should be taken to
ensure verticality
by using a wlre plurnb llne
durlng installation.
The recepEacle whlch first
receives the concrete at
the botton of Ehe vertical
shaft pipeline is called
a dash pot or kettle.
A typical dash pot ls shown
in Figure 28.
It consists of a steel cylinder, of
sllghtly
larger internal
diameter than the shaft
pipe, wlEh a thick steel base plaie for lmpact.
An
overflow pipe allows t.he concrete to pass frorn the
dash pot to the distribution
box on the slnking
scaffold or, alternatively,
directly
to the neans
of transport
underground.
The length of dash pot
between the impact plat.e and che outflow plpe is
regulaEed, depending upon how far the concrete ls
dropped dorrn the shaft,
ln order to cushion the
fall and to control concret.e f1ow.
Shafts are
being lined to a depth of 1000 n by thls nethod ar
the present time in the United Klngdon.
However,
there appears to be no restriction
on the procedure
as greater depths have been sunk and lined in South
Africa using sinllar
pracEice.

3.10.2 Transport underground

Once the concrete has reached the botton of a shaft
or drift,
various means of transport are avallable
for transfer to the point of application.
If the
concrete has been punped down a drift,
then
continuatlon
of this process r0ay be the answer with
pumps, at convenlent
the possible use of additional
staging points, for further distrlbutlon
lf
needed. Fron the boEton of shafts, pumps, placers
or transit
cars running on rails nay be enployed.
Transit cars are particularly
sultable for tunnel
construction.
At the discharge point, the translt
car can be'used to feed a traln specially
designed
to operaCe in conjunction with the Eunnel
shutter.
Flgure 29 shows such a tral-n used ln
conjunctlon nith the shutter in Flgures 24 and,
25.
In thls case the transit
car discharges onto a
feed conveyor leading directly
to a 100 m Schwlng
concrete pump specially nounted for use on ral1
tracks.
The wheel mounted scaffold is posltlvely
connected to Ehe pump and supports the pl-pework and
glves access to the doors and portholes ln the
shutter.
Hydraul-ic rams maintain contacE between
the concrete pipe and the portholes.
Transit cars
can also be run fron surface in the case of a drlft.

Figure

28.

A dash pot for receiving

concrete,
poslEioned at the bot.ton of the
vertical
shaft oioeline.

3.10.3 Concrete placing at roof level

The quesElon of casEing concrete up to the
roof 1evel has been nentloned in
excavatlon
relatLon to lnsets,
tunnels and plugs.
In tunnels
with special steel shutLers contalning porEhole
access points, Iittle
problen exisEs as pumplng
pressures can be employed to fill
the shutter to
roof level.
For an inset roof, access for
concretlng is normally through the stopend.
Concrete pipes are led through the stopend to the
farthest
extrenity
and wlthdrasn gradually
as
placlng proceeds.
Wirh Ehis process the concrete
plpe nust be situated as high as possible in the
crown, to ensure complete filJ-tng to that level as
the plpe is wlthdrawn.
Concrete containing a
superplasticizer
is needed for this particular
appllcatlon.
Poker vibrators
attached to rigid
poles are used only to asslst the alnost self
compactlng actlon.

z9

Figure

29.

A concreEe train for use in a tunnel; this example was used in the Grain Power Scation cooling
r.rater intak6
tunnels and i n c l u d e s f e e d c o n v e y o r ( r i g h t ) ,
concrete puDp (centre) and shutter
access scaffold (left).

4. Goncrete llltix Design

4.1 Introductlon
The lntroduclion
to thls paper staced Ehat wiEh a
correctly
englneered handllng system, the right
plant and suitable
nlx deslgn, concreting
underground ls not dlfflcult.
This polnt is reDesign of a sultable handling
afflrmed here.
systen ls obvlously related to access condlclons.
Once the system has been established
then lts
successful operation is dependent upon rellable
plant:
well nalntalned plant ls of priroe
inporEance.
The renainlng
factor
is the mix design
itself
and care nust be taken to provide the rlght
balance of lngredlents,
flrst
of all to sult Ehe
psrticular
oode of transportatlon
being used, and
secondly to Dake sure that the opELnum deslgn ls
achl-eved. The perfornance of the concrete during
transportaEion should be nonltored .continuously and
flne adJusCnents made regularly
to achieve thls.
In additlon Eo strength,
the mosr inportant
factor
of the nix deslgn ls to obtaln the correct
workablllty.
For underground work, wlth its
placlng environment, it is essentlal
restricted
that hlgh workabillcy
nixes are used.
Thls means
invarlably
that plastlclzing
admixtures are
In the author's oplnlon, successful
necessary.
\rith concrete underground is entirely
construction
dependent on then durlng both transportatlon
and
placlng.
Uslng plastlclzers
allows the additlon of
sater to be kepE to a nlninum ln the basic nix to
achleve high strenggh,
the hlgh workabiltty
betng
produced elnply by the addlElon of the admixture.
As a general rule,
a slump value of 125 on at. Ehe
polnt of placing should be speclfied for the rnlx.
Wlth the nornal tolerance of 25 m or 25tr of the
lntended elump, a slunp ln the range of 100 to
150 m should be obtalned at the point of
placing.
A11 losses ln slurnp durlng EransporEatlon
30

frou the batching plant to the point of placing

should be accommodaced by providlng
a sultably
For concrete dropped dovn
adJusted lnltlal
slunp.
it would be normal to
a verEi-cal plpe ln a shaft,
25 mn
deslgn for a loss ln slurop of approxinately
for each 300 n fa1l.
Hence concrete with a slunp
1000 o
approachlng 200 m Is used for llning
shafts.
Using the slunp tesE as a neans of control
for such concrete is lnapproprlate.
The DIN 1048
flow table lesc ls an alternatlve
means of Judglng
15.
concrete flow characterlstics

4.2 Normal mixes

Strength speclfications
for underground concrete
work follow Ehe relevanE Codes of PracEice 7'I3,
Grade 20 belng the lowest 1loit
for sEructural
concrete and Grades 25 and 30 belng used for water
retaining
scructures.
ShafE linlng
concrete was,
generally of a low st.rength because
recently,
until
placing conditlons and less
of the difflcult
quallfy
strlngent
conBrol procedures enployed.
The
Selby New Mlne ProJect has eoployed speclalist
ready-oixed
concrete suppliers,
of
and the quallty
boch the nlx constituents
an: the baEched concrete
has allowed higher strength nlxes to be used to the
full
in design even to the extent of considerlng
strengths
as hlgh as 60 N/nn2.
The incorporatlon
has also inproved the placlng
of plastlclzers
situation.
Typical normal nlxes for Grade 45 shaft concrete
are shonn ln Table l.
Sulphate reslsting
Portland
cement ls used for all underground work, and the
nixes illustraEed
were designed Eo satlsfy
the
requlrements of Class 4 of BRE Dlgest 250 16, for
sulphate reslsEance.
Generally the requireDents for
dropped down a nfpellne follow
p u m p e dc o n c r e t e r / .

concrete to be
the guldellnes for

Productlon and placlng Eenperatures play an

ltrportant part ln 6haft llnlng operatlons.

Table I: Typical concrete mix designs; normal shaft

Grade 45 mixes designed to satisfy Class 4 sulphate

I i - i - ^

rrLrrrrts

_ : . . ^ ^

ilrrAE5.

resistance

of

B R - ED i g e s t

250.

Si te

Selby Wistow

Selby Riccall

Supplier

Topnix

Trurnix Ltd

Topmix Ltd

Cement

Ribblesdale
420 ke/n3

Rugby Crown
460 ke/n3

BIue Circle

Ltd

Elvaston

Sand

| Blaxton

zone 3

o7o ke/n3

total

assregate
Coarse aggregate

135:l

|;39:l

Elvaston

gravel

1140 kglm:
20-5 mn
Water

Borehole

180 1ilm3
Water: cement ratio

0.43

Slunp r^rithout
plas t ici zer

/)

Plas ticizer
Slump with
plas t icizer

mm

Cement replacement

lltZ

| Farnham gravel

I fO mrn
I ZO mm

Varies with

shaft

materials

The trso fundanental

obJectlves of uslng cenent
replacenent mlxes are to nlnimlze
the heat of
hydratlon
galn, and hence reduce the possiblllty
of
tenslle sEresses due to thernal contractlon,
and t.o
reduce cost.
Provided the sulphate resistance,
28
day cube strengEh and nlx workability
requLrenents
are also satisfled,
then lt may be beneflcial
to
use such mixes for partlcular
secEions of the work.
Tvo such mlxes are shown in Table 2.
The flrst
rnlx
ls suitable for shaft lining construcfion
and the
second could be used for bulk filllng
for, e.g. a
plug for stopplng water lngress.
Both these nixes
show itrproved wdrkabllity
qrlthout
characteristics
the use of plasticizers
but the high slunps
required ln underground work dictate
Ehe lncluslon
of the latter
as well.
The first
mix is capable of being dropped down a
vertical
pipe for shaft use but its low early
strength gain extends the formrrork stripping
time.
It has nof been used, at the presen! tlme,
for concreting a linlng
in frozen ground because
the low heat gain could lead to det.rinental effects
when subjected to freezing action. Both rnixes are
sultable for pumplng,

I Blaxton

gravel

350 kg/n3
700 kglm3

1120 kg/m3

Borehole
186 1ilrn3

Borehole

0.40

0.42

75 umr

75m

Flocrete N, 0.18 to 0.36 li

A minlnum leoperature
of 19.'C ls desirable
for
concrete to be cast against an ice nall in order Eo
asslsE in overconing the freezlng action.
However,
temperatures above thLs value lncrease the chances
of cracking ln the finlshed
linlng
because, coupled
rilth the heat of hydratlon
butld up, the
contraction
on coollng to belolr 0"C is lncreased.
In condltions
where the ground ls not frozen, nuch
lower placlng temperatures should be used to
nlnlnize
the rlsk of early thermal contractlon
crackLng.

4.3

tl^

065 kglrn3

Selby

4{+U Kglm"

| Farnham Zone 2

Zone 2

615 kglm3
Sand % of

I North

185 lilm3

per 50 kg cement

depth but generally

160 rnmand upwards

4.4 Admixtures
The success of underground concreting relies upon
the inclusion
of workability
agents ln the nLx.
In
the last five and a half years, the author's
experience of the use of plasticizers
and
superplastlcizers
in concrete has been largely
associated with the products of CemenEatlon
Chenicals Linited,
which is a sister company of
Cementation Mlning Lirnited.
Close liaison between
these two cornpanles, and Cenentaclon Research
Llmited, has enabled the enployroent of adnixtures
to be developed to the full extent wlthout any
detrimental
effecls
in the concrete.
Their use can
now be regarded as specialisE conpany expertise.
The produccs used have been Flocrete N, Flocrete R
and Supaflo.
Flocrete N is a plasticizer,
in brown
llquid
forn, based on a processed calcium
ligosulphate.
Flocrete R, which is a retarding
plasticizer,
ls a polyhydroxycarboxyllc
acid
derivatlve,
supplied as a broran non-toxic aqueous
solutlon.
Supaflo ls a superplasticlzer,
supplied
as a non-toxlc
brown llquid.
It conEains synthetic
sulphonated naphthalene/fornaldehyde
condensates.
Flocrete
N and FlocreEe R are added in snall
dosages whlch nust be controlled
at the nlxing
polnt.
Supaflo ls added ln much larger quantltles
and can be added straighE into the rotatlng
drun of
a mixlng truck Just prlor t.o dlscharge.
In this
way, concrete which has been standlng for some tlne
can be re-activated.
Flocrete R can be directly
mixed wlth Supaflo Ln certaln proportions to
provide a retarding
superplastlcizer.
Typlcal
dosages recommended by the manufacturer are glven
in Table 3.
FlocreEe N is used for oormal shaft construcEion
and for requlremenEs close to the shaft borrom.
JI

Table 2: Typical

Application,

concrece mix designs;

grade

mixes concaining

cement replacement

materlals

Grade 45

Bulk fil1ing,

Shaft lining,

Si te

North Selby

Supplier

Topnix Ltd

Total cementitious
content

500 kg/n3
( 3 0 2 O P C , 7 0 7 "C e m s a v e )

Sand

Blaxton Zone 3

Topnix Ltd
400 kgln3
(250 kr/nr OpC,
150 kg/m3 pfa)
ElvastonZone2!,
770 kg/n3

595 kg/rn3
Sar.d % of
aggregate

Grade 30

total

34"t

Coarse aggregate

42"t

Blaxton gravel
1150 kgln3

Water

Elvaston gravel
1050 kglrn3

180 liln3

180 liln3

LIater: cement ratlo

0.36

0.45

Slunp without
plas t icizer

60 rnn

50m

Plasticizer

Flocrete N

Flocrete N

Slurop wi th
plasticizer

160 mm

160 rnrn

Flocrete R ls enployed where long dlstances need to

be travelLed underground.
Supaflo, or conblnaElons
of Supaflo and Flocrete R, are uged where
partlcularly
fluld
nlxes are requLred.
Such areas
are the Eopplng up of shaft wa1l pours to Deet up
nlth the prevLous lift,
areas nhere congestlon of
relnforcenent
occurs such as fan and alr drlft
mouthings, and roof pours where lntlnate
conEact
vlth the overhanglng ground nust be achleved.

Table 3: Manufacturer's

plasticlzlng

adnlxtures

NAME

FUNCTION

DOSAGE

Flocrete

Plasticlzer

0.14-0.18 1ltres per 50 kg of cement.

(Double dosages, i.e. 0.18-0.36 litres
per 50 kg of cement, have been used with
the Manufacturer's approval).

Flocrete

Supaflo

JL

reconmended dosages for

Retarding

plasticizer

Superplasticizer

0.12-0.26 lltres per 50 kg of cemenr for

a retardatlon of 3 to l0 hours.

3-5 11tres/nr

of concrere.

5. Gonclud.lng Remarks
The paper has described the Eypes of concrete
structure
to be found ln underground developnent
work and discussed baslc deslgn prlnciples.
Methods of consEructLon and mix desLgns have also
been included.
Throughout the paper, every attenpt
has been Dade to discuss the varlous aspects ln
true perspective with che nining environmen!.
It
nust always be remernbered that conditlons
are
from those Ln surface works constructlon
different
and sometimes underground conditlons for concretlng
are not ldeal.
FLgure 30 ls a vieid of a shaft
botton showlng typical working condltlons.

Figure 30.

Typical shaft
A u st r a 1 i a ,

b o t E o r ns h o w i n g a c t u a l

Nevertheless,
the standard of concreEe work ls
Lmprovlng rapidly,
largely as a result of the
employment of speclallst
concrete suppliers,
quallty
better
control and luproved transporEatlon
and placlng Eechniques uslng plastlcizlng
adolxture6 1n conjunctlon with modern plant
developnents.
Hlgh workablllty
concrete need no longer be
achieved by addlng excesslve amounts of water to the
mix after
lE has left
the nlxlng plant.
Adrolxtures
can now be used to provide hlgh workabtltty
concrete wlthout affectlng
the water: cement ratlo
or the strength.

working conditions.

Mount Isa copper mine A.10.S shaft,

6. Beferences
I.

Design of concreEe shaft llnings.

AULD, F A.
Proc. Instn. Clv. Engrs. Part 2, L979,67,
Sept. pp. 8L7-832.

2.

AULD, F A. Ultimate strength of concrete shaft

on design' Proc. of
and iEs influence
llnings
t.he Synposium on SErata MechanLcs, Universlty
1982.
of NewcasEle upon Tyne, 5-7 Aprtl
Publlshing
Company, 1982.
Scientiflc
Elsevier
pp. 134-140

3.

the
WILSON, A H.
A nethod of esLiEating
required in
closure and sErength of lining
drivages surrounded by a yield zone. Int. J.
Rock Mech. Min. Scl. & Geomech.Abstr. Vo1.l7,
19 8 0 . p p . 3 4 9 - 3 ' 5 .

4.

The art of
SZECHY,K.
Kiad6 Budapest, 1967.

MBCEWICZ, L V,
Stabiltty
of Eunnels under
Water Power, June, July, August,
rock load.
1959.

6.

VOSS, K H.
InnovaElons and recent experlence
w i E h R O Mb u n k e r s u n d e r g r o u n d .
Colliery
Guardian, June 1981'. pp. 236-24O.

7.

B R I T I S H S T A N D A R D SI N S T I T U T I O N .
BS 5337:
L976.
Code of pracEice for the structural
of concreEe for retaining
aqueous liquids,
British
Standards Institutlon,
London.

lunnelling.

Akad6niai

use

8.

SIMPSON,D.N.
Underground staple shaft
bunkers.
Colllery
Guardian, YoI.229, No. 6,
June 1981. pp. 230-235.

9.

NATIONAL COAL BOARD. Design and construction

of
sEaple shaft bunkers. Mining DepartmenE Working
Party Report.
National Coal Board, London
1981.

10.

B R I T I S H R E A D Y M I X E D C O N C R E T EA S S O C I A T I O N .
B R M C AA u t h o r i s a t l o n
Scheme for Ready Mixed
5th Edition.
Concrete.
BRMCA,ShepperEon,
March 1982.

11.

B R I T I S H R E A D Y M I X E D C O N C R E T EA S S O C I A T I O N .
DirecEory of Menbersr Depocs 1982. BRMCA,
Sheppercon, l982.

12.

B R I T I S H A G G R E G A T EC O N S T R U C T I O N
MATERIALS
INDUSTRIES, (BACMI).
Code for the produccion
and delivery
of. ready-nixed concreEe. BACMI,
London,1982.

13. BRITISH STANDARDS

INSTITUTION. CPIIO: PaTE 1:
The structural
1972.
use of concrete. Part 1.
British
Design, naterials
and workmanship.
London.
Standards Institutlon,
I4.
.

I5.

B R I T I S H R E A D Y M I X E D C O N C R E T EA S S O C I A T I O N .
7th edltion.
The
Register of test houses
British
Ready Mixed Concrete Association
Ltd.
January 1981, plus AddendumMarch 1982.
C E M E N TA N D C O N C R E T EA S S O C I A T I O N .
Superplasticizlng
admixtures in concrete.
ReporE of a joint
CM/C6CA l.Jorklng Party.
C e m e n Ea n d C o n c r e t e A s s o c l a t i o n ,
Slough,
pp. 32.
December 1976.
Publlcation 45.030.

l-6. BUILDING RESEARCH

ESTABLISTTMENT
D.i g e s t
Concrete in sulphate-bearing
soils and
groundwaters.
Her Majesty's Stationery
London, June 1981.
34

250.
Office,

17.

ESTABLISI{MENT. Guide to
BUILDING RESEARCH
Her Majescy's Stationery
concreEe punping.
Office, London, 1972.

?.GilossarJrof ltllinin$ Terms

(ln accordance with
Terns )
Air

An inclined
ventilation

drlft

Backshee!s

Backwall

BS 3618, Glossary

grouting

Sheets of naferials
inpervLous
to waEer nhich
are placed beEween an
excavation face and the
cast in situ concrete
llning
to exclude strata
warer from Ehe fresh
concreEe.
The injection
of grout, or
other sealing or
consolldating
coopound,
behind rhe finished
lining
of a shaft to seal off
residual vater and/or to
preserve the lining.
The solid rock underlying
superficial
deposits.

Bulkhead

A hratertight dan conEalning

sone forn of door or
removable plate.

ConpeEenE rock

A strong rock which may not

require supporE in an
excavation.

Crlb

D e g r a d at i o n

DowncasE shaft

A nethod of consolldating
water-bearing
strata,
to
prepare it for shafc
sinking,
in whlch a
freezing agent (usually
brine) is circulated
dis_posed
through suitably
boreholes drilled
inEo the
straca around the site of
the shaft

roadway for
purposes.

B e dr o c k

Convergence (closure)

process

Freezlng

of Mining

Movement of roof and floor

towards each oEher after
renoval of nineral.
The
rate of convergence is
rueasured as elEher:
1. the convergence for a
given advance of the
face, or
2. the convergence in a
given time.

The process of injecting

cement, or other material,
to improve Ehe sErength of
the strata or !o reLard or
Prevent the passage of
liqulds or gases.

Ilead f r ame

The sErucEure at the top of

the shaft on whlch the
winding pulley or sheaves
are mounted.

Inset

An opening or entry froo

shaft Eo an underground
roadway or charober.

Measures

A series of beds or srrata;

a tero now generally
liroited to rocks within
the
Coal Measures.

Plug

A seal construcLed in a
mine roadway Eo prevent or
conlrol
lhe entry of water
into mine working.

Scaffold

(or

stage)

ShafE

Ring of concrete set so as

to forn Ehe foundation
for
a secEion of walllng
in a
sinking shaft.
Inadvertent
breakage of
mineral
in rnining,
handling,
Eransporta!ion
s Eorage .

Grouting

Drift

A roadway driven
surface.

Drivage

A roadway drlven
in the
solid coal or stone.

Fan drift

An alrway leading
froo
mine shaft to a fan.

Freeze cellar

Tenporary surface strucEure

whlch houses Ehe brine main
feed systen interconnect.ing
the freeze Eubes installed
in Ehe boreholes (see
Freezing process).

A vorking platforn
suspended in a shaft
s inking ,
A vertical
or steeply
incllned
excavaEion of
limited
width in relatlon
to its deplh, nade to
provide access Eo
underground workings.

Shaft

collar

The initial
foundations
forming the mouth of a
shaft.

Skip

A shafE conveyance designed

prinarily
for che bulk
handllng of mineral.

Upcast shaft

A shaft through
leaves a mine.

or

A shafE through whlch fresh

air is drawn or forced inEo
a mine.

Well-dewaEering

frorn the

* Not deflned

whlch alr

Removal of straca water by

well points or deep wel1s.

i n B S 3 6 1 8 , G l o s s a r y of Mining

Terros.

35