A Modification of Pile Unit Skin (f) of Frictional Resistance (Q
s
)
on Clayey Layer at Central of Jakarta
Putera Agung Maha Agung
1
, Andreas Rudi Hermawan
1
, and I Ketut Sucita
1
1
Department of Civil Enginering, Politeknik Negeri Jakarta, Depok, Indonesia
Keywords: frictional resistance, pile foundation, CPT, and PDA test.
Abstract: The evaluation of pile unit skin friction (f) is important and difficult in determining frictional resistance (Q
s
)
of single pile. A modification was conducted on curves and table design of (f) in clayey soil from Nottingham
& Schmertmann and Schmertmann methods. PDA test was used as the valid data to compare the prediction
analysis result using these methods. Resistance friction (Q
s(u)
) and (Q
s(Ru)
), respectively of single pile were
obtained by 5 random points of CPT analyzed by Schmertmann methods and 2 points of PDA test evaluated
by CASE and CAPWAP methods from study site. From the result of modification of unit skin friction analysis
using CPT data approaching to the real data from PDA test results.
1 INTRODUCTION
Generally, cone penetration test (CPT) is extensively
used in the building project. Cone penetration testing
(CPT) is an easy, a fast and a reliable means of
conducting building design site investigations for
exploring soils and soft ground for support of
foundations. For the small to medium project,
engineer has to design with using CPT data only, so
they must search the confirmatory data through some
correlation between parameter from CPT data results
to complete the shortage data. Thus, the all prediction
for frictional resistance (Q
s(u)
) parameter design of
axial bearing capacity (Q
u
) from CPT results must be
examined by a loading test results at the field in
determinating the safety factor (SF).
There are many methods for evaluation (Q
s(u)
)
based on CPT data (Aoki and De Alencar (1975),
Clisby et al (1980), Schmertmann (1978), de Ruiter
and Beringen (1979), Bustamante and Gianeselli
(LCPC/LCP) (1982), Tumay and Fakhroo (1982),
Philipponnat (1980), Price and Wardle (1982)
methods. However, it was not for all methods showed
the best capability (Titi and Abu-Farsakh, 1999) in
predicting of (Q
s(u)
) using (PPC) piles driven into a
certain area. This research effort was focused on the
applicability of one of CPT methods to predict the
frictional resistance of piles from CPT data
(Schmertmann, 1978). The predicted capacity (Q
s(u)
)
using CPT data was compared to the reference pile
load capacity (Q
s(Ru)
) obtained from the pile load test
using PDA method. The CPT method were used to
investigate the load carrying capacity of square
precast prestressed concrete (PPC) piles of 30 cm in
size driven into Jakarta clayey soil (SNI 2847, 2013).
Criteria for acceptance of (Q
s(u)
) (ultimate frictional
resistance from CPT) should be equals or less than ≤
(Q
(sRu)
) (from PDA results). Some previous studies
for clayey soil, Cummings et al, (1950), Seed and
Reese (1955), Bjerrum et al. (1958), Soderberg
(1962), Begemann (1965), Tomlinson (1957), and
Poulos (1989), etc were suggested to determine the
unit skin friction (f) in determining the frictional
resistance (Q
s(u)
) of single pile by direct and or
indirect approaches. This study proposed the
modification parameter analysis for unit skin friction
(f) in determining (Q
s(u)
) of clayey soil layers at
central of Jakarta.
2 METHODOLOGY
2.1 CPT Data
Soil investigation uses a set of CPT equipment
complete with the auxiliary devices. The CPT is a
light weight model with a compressive capacity of 2.5
tons. Conus used is friction cone type (biconus type)
with a cross-sectional area unit of 10 cm
2
, area of
blanket 123 cm
2
. CPT is carried out continuously at
intervals of 20 cm depth penetration to show
maximum cone (tip) resistance and maximum shear
126
Maha Agung, P., Hermawan, A. and Sucita, I.
A Modification of Pile Unit Skin (f) of Frictional Resistance (Qs) on Clayey Layer at Central of Jakarta.
DOI: 10.5220/0009954100002905
In Proceedings of the 8th Annual Southeast Asian International Seminar (ASAIS 2019), pages 126-131
ISBN: 978-989-758-468-8
Copyright
c
 2022 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

of 250 kg/cm
2
, or up to a maximum depth of 30
meters. Data set presented are the cone tip resistance
and the total friction (q
c
) and ratio local friction (t
f
)
against cone tip resistance or (t
f
/q
c
) or friction ratio
(F
R
) values to a maximum depth of 30 meters. Table
1 shows the results of the soil investigation using CPT
shows in the table below related with maximum depth
of CPT, depth of hard soil, t
f
and q
c
values for all soil
layers at the surface area. Table 2 identifies that the
estimation of geostratigraphic profile using several
methods (Begemann, 1965; Schmertmann, 1978; and
Robertson and or et al, 1986; 1990). Table 3 shows 5
(five) CPT data (S-1 to S-5) provides the information
of hard layer depth with (q
c
) value between 60 < q
c
<
150 kg/cm
2
and thickness of the bearing layer with
(q
c
) value > 150 kg/cm
2
. Then, Figure 1 shows that
geostratigraphic soil profile based on cone
penetration test (CPT) of study site. Based on the 5
(five) CPT (S-1 to S-5), it could be indicated the
condition of surface layers consisting of medium to
stiff silty clay with cone resistance (q
c
) values
between 27 to 34 kg/cm
2
and at the depth between
0.40 to 3.60 m.
CPT data normally can be used to determine the
other of soil parameter using some correlations
required for deep foundation design, especially in
determining frictional resistance of single pile (Q
s(u)
).
From some previous design reports and studies,
Schmertmann (1978) method was selected and
considered suitable for study area, besides the method
was widely used CPT methods in determining bearing
capacity (Q
u
) in Indonesia.
Table 1: The results of CPT data.
2.2 PDA Data
The PDA test is to evaluate the ultimate load
carrying-capacity (Q
u
) of the pile, the integrity /
integrity of the pile and pole drop. PDA test normally
are used as field test additional to replace the
conventional loading test. Data results of PDA test
was obtained from 2 locations of pile foundation
system configuration at a sub-structure of BPJS
Building of Central Jakarta project (See Appendix).
All calculation results of (Q
(sRu)
) by PDA test
actually uses top force pile and velocity signals,
obtained using instrumentation or device, such as :
Table 2: The results of geostratigraphic profile from CPT.
Table 3: The results of hard and bearing layers from CPT.
piezoelectric accelerometers and bolt-on of strain
transducers attached to the pile near its top. PDA
conditions and calibrates these signals and velocity.
Using case method solutions, the PDA calculates the
results on BPJS Building project site (Figure 2)
described in the following section. PDA test were
applied in two piles load testing sites for axial bearing
capacity and one pile for lateral displacement. To help
examine the soil conditions and design calculation,
the results of the investigations which nearest the
PDA pile tested for CPT-S1 and CPT-S2 as shown as
Table 1; 2; and 3.
Pile testing data results are shown from Table 4 to
6. Table 4 shows the existing pile data for evaluation
of bearing capacity and settlement. Table 4 shows the
maximum compression and tension stresses results
from field testing. Table 5 identifies the PDA test data
reading result from field test and after analysis using
manually CASE analysis and CAPWAP (Case Pile
Wave Analysis Program) software. Both
measurements and analyses generate the end bearing
capacity (Q
b
) and shaft friction (Q
s
). However, this
study will discuss shaft or skin friction (f) only as
shown as with “RED ELLIPSE-CIRCLE” on the data
of Table 6. This frictional resistance from PDA test
(Q
(sRu)
) or “Actual Values” will be compared with the
calculation using CPT data (Q
s(u)
) or “Estimation
Values” for this study.
A Modification of Pile Unit Skin (f) of Frictional Resistance (Qs) on Clayey Layer at Central of Jakarta
127

Figure 1: Soil profile based on (CPT) parameters.
Table 4: Pile data for PDA test.
Figure 2: Piling and instalation of PDA test.
Table 5: Maximum compression and tension stresses.
Table 6: PDA analysis data results (CASE & CAPWAP)
2.3 Frictional Resistance using CPT
Estimating the frictional or skin resistance (Q
s
) of
piles in clay layers is almost as difficult a task as
estimating that in sand layers, due to the presence of
several variables that can not easily be quantified.
Several methods for obtaining the unit frictional
resistance of piles are described in the literature
(Vijayvergiya and Focht, 1972, etc). However, in this
study some analyses use Nottingham and
Schmertmann (1975) and Schmertmann (1978) only
in determining (Q
s(u)
).
The correlation to evaluate unit skin friction (f) in
clay (with  = 0) to be:
 Generally, axial bearing capacity equation:
ub s
QQ Q

 (1)
 Frictional resistance from CPT data (Q
s(u)
):


.'...
su c
QfpL fpL 

 


(2)
 Unit skin friction can be determined by:
'.
c
f
f


(3)
 The variation of (’) with the frictional resistance
(f
c
) is shown in Figure 2.
 Where ( equals an empirical adhesion factor.
The approximate variation of the value of ( is
shown in Table 7. It is important to realize that the
ASAIS 2019 - Annual Southeast Asian International Seminar
128

values of a gives in Table 7 may vary somewhat,
since ( is actually a function of vertical effective
stress (’
o
) and the undrained cohesion (c
u
).
Figure 2: Variation of f
c
/ P
a
and ’ (Nottingham &
Schmertmann (1975); Schmertmann (1978)).
Table 7: Variation of f
c
/ Pa and 
(Terzaghi, Peck, and Mesri (1996); Das, 2007).
From the detail explanation above, in determining 
value requires laboratory testing for undisturbed
samples. However, for this study, soil investigation
was carried out CPT only. Thus, this study conducted
needs to propose a modification  values in
determining pile unit skin (f) from the comparison
between (Q
s(u)
) and (Q
s(Ru)
), so that it would be
suitable for study site in determining (Q
u
) of a pile.
3 RESULT AND DISCUSSION
Frictional resistance analysis based on CPT
(Schmertmann, 1978) (Q
s(u)
) and PDA (CASE and
CAPWAP methods) (Q
s(Ru)
) data are compared each
other and obtained the Figure 3. In the field, the
position of CPT-S1 is near PDA-3, and also S-2
closes to PDA-4, respectively.
Figure 3: (Q
s(u)
) and (Q
s(Ru)
).
From Figure 3, parameter of (f) or (f
c
) and  and or ’
can be determined by back analysis using average of
line equation of (Q
(s(Ru)
) directly. Thus, to calculate (f)
or (f
c
) can be used the Equation (4) and (5),
respectively:

()uRu
Q
f
pL




(4)

()
'
uRu
c
Q
f
pL





(5)
where
'.
c
f
f


.
And, the results of modification of Nottingham &
Schmertmann (1975) and Schmertman (1978) can be
shown in Figure 4 and Table 8.
Since the study is only for concrete piles, the Figure
4 is applicable for deep foundation of pile made from
reinforcement concrete or square precast prestressed
concrete (PPC) piles system. And, Figure 4 is only
valid for clayey layers at central of Jakarta. However,
this study can be developed for another places in
Indonesia which is same as Jakarta soil
geostratigraphy.
A Modification of Pile Unit Skin (f) of Frictional Resistance (Qs) on Clayey Layer at Central of Jakarta
129

Figure 4: Modification relationships between variation of f
c
/ P
a
and ’ values
Table 8: Modification of Terzaghi et al (1996)
Terzaghi et al (1996)
Clayey layer of
Jakarta Central
c
u
/P
a
 Range of 
0.1 1.00 0.83 – 1.21
0.2 0.92 0.76 – 1.11
0.3 0.82 0.68 – 0.99
0.4 0.74 0.61 – 0.90
0.6 0.62 0.51 – 0.75
0.8 0.54 0.45 – 0.65
1.0 0.48 0.40 – 0.58
1.2 0.42 0.35 – 0.51
1.4 0.40 0.33 – 0.48
1.6 0.38 0.31 – 0.46
1.8 0.36 0.30 – 0.44
2.0 0.35 0.29 – 0.42
2.4 0.34 0.28 – 0.41
2.8 0.34 0.28 – 0.41
Note: Pa = atmospheric pressure  100 kPa
4 CONCLUSIONS
Study analysis investigations have indicated that
unit skin friction (f) in determining frictional
resistance (Q
s
) on clayey layers of Jakarta Central
reaches about ± 17 to 18 percent of the previous
studies (Nottingham & Schmertmann, 1975;
Schmertman, 1978). This matter, it can be shown in
Figure 4 and Table 8, where  and or ’ values on
each modification has a certain range of these values.
However, in application it should be considered with
vertical effective stress (’
o
) and the undrained
cohesion (c
u
) from laboratory data for undisturbed
sample.
These values obtained were within ranges established
by governmental authority regulations. Pile unit
friction (f) showed significant changes during
instalation for any time period.  and or ’ values of
CPT data proved more sensitive than c
u
values
changes for determining frictional resistance during
the pilling. Losses of unit friction (f) can increase with
pore water pressure around pile shaft.
ACKNOWLEDGEMENTS
This work was supported by Tambora Consultant
Company for Deep Foundation System Designer;
Tribina Wahana Cipta for Soil Investigation of CPT
data; Geotesting Utama Engineering for PDA data;
and the Central BPJS Office as the project Owner.
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APPENDIX
PDA DATA
A Modification of Pile Unit Skin (f) of Frictional Resistance (Qs) on Clayey Layer at Central of Jakarta
131