TMH-6 - ST6 PDF

METHODST6
MEASUREMENT OF THE IN SITU STRENGTH OF SOILS BY

THE DYNAMIC CONE PENETROMETER (DCP)
1
SCOPE
This method descnbes the determination of the "rate of penetration of the Dynamic Cone Penetrometer (DCP) into a natural of-compacted material by virtue
of the built-in sliding hammer _ The penetration rate is inversely proportional to
the resistance of the ground to the penetration of the cone of the OCP and may
be rela1ed. inter alia. to the in SItu CSR or soil density (see 5,1).
APPARATUS
2.1
Dynamic Cone Penetrometer as illustrated in Figure ST6 f WIth the appropriate

spanners, spare cones, rods, etc, (see 5.2).
2,2
A pick or hand auger.
2.3
A spade.
2.4
A measuring tape. 2 m long.
2.5
Traffic cones. warning signs and flags as required .
M~THOO
Assemble the DCP as shown In Figure ST6:1 ensuring that the parts are fitting
properly and that the hammer can slide freely . Place the tip of the cone on the
site 10 be tested (see 5.2). Hold the DCP vertical!y and by means of the hammer knock the cone into the surface up to the zero mark, which is the paralle!sided shoulder portion ( 3 mm wide) just above the cone-shaped tip.
Attach the measuring rod to the DCP and zero the sliding scale,
While holding the DCP vertically. lift tt1e hammer as far as it can go and allow it
to fall freely and stnke the anvil. driving the cone into the ground surface.
The penetration can be read off after each blow of the hammer or after as many
blows as are practical or required for the purpose of the test (see 5.3). Record
the penetration (to the nearest 1 mm) and the number 01 blows on Form ST61
or a similar form (see 5.4).
On completion of the test, the DCP is extracted by ramming the hammer
against the upper stop - usually after the measuring scale has been detached
to prevent damage (see 5.5).
The strength of layers deeper than the reach of the OCP can be measured by
removing some or all of the overlying material with a pick and spade or using a
hand auger. At the start of the test the depth below the original datum level of
the material to be tested is measured, using a tape measure, and recorded.
4
CALCULATIONS
4.1
The OCP penetration depths in mm are plotted against the number of blows on
Form ST6/1 and a penetration curve is drawn, the angle of which is the penetration rate, known as the "OCP number" (ON) in mm/blow. A consistent slope
angle thus indicates a consistent ON for that particular zone.
Special methods
Draft TMH6. PretOfia. South Afnca, 1964
19
4.2
In situ shear strength (CBR)

From the curve, the ON (in mmi blow) at different zones or the mean over a chosen depth may be calculated to obtain the in Situ shear strength of the particular
zone. The ON of a specific zone is obtained by dividing the zone thickness by
the number of hammer blows to penetrate that zone.
From Table' the equivalent in situ CBR value o f that zone can be obtatned ,
TABLE 1
~-------
DCP number
(mm !BlOW)
IN SITUC8R
DCP number
(mm.,BLOW)
-- - -
110
17
75
IN SITUCBR
--....- ...-..
.... .. .. --.-~-.~- ..
. ....
~-.----
12
11
55
18
19
6
7
45
20
35
22
8
9
30
25
28
32
6
5
38
10
25
22
11
20
12
18
13
14
16
15
15
14
16
13
48
60-10
+80
10
3
2
NOTES
51
The OCP may be used to assess the density of a fairly uniform material by relating density to penetration rate (ON) on the same material. In this way undercompacted or "soft spots" can be identified, even though the OCP does not
measure density directly,
A field DCP measurement results in a field or in situ CSR and will normally not
correlate with the laboratory or soaked CSR of the same materiaL The test is
thus intended to evaluate the in situ strength of a material under prevailing conditions.
If a number of OCP penetrations have to be compared with one another (or with
target values). or when the mean values for a section of road have to be esti
mated, the DN values may be recorded on the DCP fayer-strength diagram as
illustrated in Form ST6i2
5.2
The cone must be replaced when its diameter has been reduced by 5 per cent
or it has been viSibly damaged,
5,3
Readings after each blow are recommended for thin layers. say up to 150 mm
thick. but readings after every fifth blow are usuaUy sufficient. The regularity of
readings also depends on the rate of penetration. Readings should be taken
more often with very soft material than with resistant material.
5.4
The results may be plotted on the work sheet as the readings are taken, to get
an immediate indication of the penetration rate for each layer.
SpecIal methods
20
Draft TMH6. Pretoria, South Africa , 1984
5.5
If necessary. sampies of the rnatsriai can be taken after the OCP test using a
hand auger. or a pick and shovel for harder material.
REFERENCES
1.
KLEYN, E G. The use of the Dynamic Cone Penetrometer (DCP). Transvaal Roads Department. Report l2/74, Pretona, July 1975.
2,
KLEYN, E G, MAREE. J H and SAVAGE, P F. Application of a Portable

Pavement Dynamic Cone Penetrometer to determine in situ bearing properties of road pavement fayers and subgrades in South Afrjca. ESOPT II,
Amsterdam, 1982.
3.
KlEYN, E G, and SAVAGE. P F. The application of the Pavement DCP to

determine the bearing properties and performance of road pavements. In
ternational Symposium on Bearing Capacity of Roads and Airiields, T roodheim. NOfway, 1982.
4.
KLEYN, E G, VAN HEERDEN. M J J, and ROSSOUW, A J. An investIga-
tion to determine the structural capacity and rehabilitation utilization of a

road pavement using the Pavement DynamIC Cone Penetrometer. International Symposium on Bearing Capacity of Roads and Alriields, Trondheim, Norway. 1982.
5.
KLEYN, E G. and VAN HEERDEN. M J J. Using DCP soundings to optimize pavement rehabilitation Annual Transport Convention, SessIon G:
Transport Infrastructure. Johannesburg. RSA, 1983.
Special methods
Draft TMH6. Pretoria. South Africa. 1984
21
f.4--.- HANDLE
~
_UPPER 5TO P
...
HAMMER (13 kg)
-r---
THE CONE
ZERO MARK
-_J---I.!
!,I
,..
to
to
SCALE
I _'!
i'-CONE ANGLE 60
~
I
~I ~
ANVIL -WH ERE RODS SCREW
UPPER
eLi P
TOGETHER
- REFERENCE POINT FOR SCALE
16 mm
S TEEl RODS
MEASURIN G ROO WITH ADJUSTABLE SCALE
LOWER eLi .p
ZERO MARK ON TEMPERED CONE
NOT
ACCORDING TO SCALE
FIGURE 5T6I1
22
THE DYNAMIC CONE PENETROMETER
Specla! methods
Ofaft TMH6. Pretoria. Sovth Africa. 1964
RQAO _ __
PAD
km
4
NUMBER OF BLOWS I AANTAL SLAE )( 5

6
1
a 9 10 II 12 13 14 I ~
+-
...
FORM 5T6I1
1
fO
18
-. -- - ._.....- -_.- - -_.
770
5
'7
40
60
_v_
i
i
-. ~
16
1\
!
1 j
II' 12
-t13
-- i--t14
15
16
17
Ie
19
80
800
20
OCP PENETRATION DEPTHS VERSUS NUMBER OF BLOWS
Special methods
Draft TMH6, Pretona . South Africa, 1984
23
ROAD I PAD : _________________________ _
OATE! DATUM : __________ ___ _
DISTANCE / M'STANO ' __ . _______ _____ _
OR/OF .. m ' ___ ___ _____ _ ______ __ __ __
caR
KDV
o
i"')
~
N
Si
o
!!
10
0 .....
0
10
!
E
E
XW
..... 1-
n.[!j
w_
oo
ON:
"
FORMST6I2
24
,.,
-:t
ID
co -
o
N
,.,
-:t
IJJ
co
DCP LAYER - STRENGTH DIAGRAM
Special methods
Draft TMH6. Pretoria, South Africa, 1984

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METHODST6

MEASUREMENT OF THE IN SITU STRENGTH OF SOILS BY

Dynamic Cone Penetrometer as illustrated in Figure ST6 f WIth the appropriate

A pick or hand auger.

A measuring tape. 2 m long.

Traffic cones. warning signs and flags as required .

Draft TMH6. PretOfia. South Afnca, 1964

In situ shear strength (CBR)

Draft TMH6. Pretoria, South Africa , 1984

KLEYN, E G, MAREE. J H and SAVAGE, P F. Application of a Portable

KlEYN, E G, and SAVAGE. P F. The application of the Pavement DCP to

KLEYN, E G, VAN HEERDEN. M J J, and ROSSOUW, A J. An investIga-

tion to determine the structural capacity and rehabilitation utilization of a

Draft TMH6. Pretoria. South Africa. 1984

HAMMER (13 kg)

ANVIL -WH ERE RODS SCREW

- REFERENCE POINT FOR SCALE

MEASURIN G ROO WITH ADJUSTABLE SCALE

THE DYNAMIC CONE PENETROMETER

NUMBER OF BLOWS I AANTAL SLAE )( 5

-. -- - ._.....- -_.- - -_.

OCP PENETRATION DEPTHS VERSUS NUMBER OF BLOWS

Draft TMH6, Pretona . South Africa, 1984

ROAD I PAD : _________________________ _

OATE! DATUM : __________ ___ _

DISTANCE / M'STANO ' __ . _______ _____ _

OR/OF .. m ' ___ ___ _____ _ ______ __ __ __

DCP LAYER - STRENGTH DIAGRAM

Draft TMH6. Pretoria, South Africa, 1984

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OATE! DATUM : ________ _ _

DISTANCE / M'STANO ' . _ _ _

OR/OF .. m ' _ _ _____ _ ____