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Soils and Foundations
Soils and Foundations 2012;52(1):59–680038-0
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journal homepage: www.elsevier.com/locate/sandfAxial bearing capacity of socketed single cast-in-place piles
Cem Akgu¨nern, Mustafa Kirkit
Yildiz Technical University, Civil Engineering Department, Davutpas-a, Esenler, 34220 _Istanbul, Turkey
Available online 7 February 2012Abstract
In this paper, a comparison is made of the axial bearing capacities estimated with pile load tests and empirical methods for seven rock-
socketed single cast-in-place piles constructed in Turkey. The unconfined compressive strength of rock, obtained from pressuremeter
tests, is used in the empirical correlations. It is commonly assumed that axial loads applied at the top of a socketed pile are transferred to
the sides of the socket until a certain displacement is reached and that the end bearing capacity contributes only after this threshold
displacement is exceeded. In practice, however, due to typically small displacements occurring in rock sockets, most, if not all, of the
axial capacity is estimated to derive from the side shear. The limit displacement up to which the side frictional capacity of a socketed pile
governs and the end bearing capacity starts mobilizing is examined, and no such threshold value is observed based on the findings of this
study. Nevertheless, the bearing capacities obtained from the empirical correlations agree reasonably well with those calculated from pile
load tests, when a systematic approach for estimating the threshold value from pile load tests is utilized and the unconfined compressive
strength of socketed rocks can be estimated within reasonable accuracy applying actual field conditions.
& 2012. The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
Keywords: Base resistance; Bearing capacity; Empirical methods; Mobilization capacity; Pile load test; Side shear resistance; Socketed cast-in-place pile;
Vertical load (IGC:E04/G02)1. Introduction
Rock-socketed cast-in-place piles are typically selected
when the large loads of superstructures, such as high-rise
buildings, tower structures and bridge footings/abutments,
need to be transferred to competent bearing strata so as
to restrict deformations within the serviceability limits.
Furthermore, the use of drilled piles socketed into rock as12. The Japanese Geotechnical Society. Production and
ier B.V. All rights reserved.
er responsibility of The Japanese Geotechnical Society
df.2012.01.012
oduction and hosting by Elsevier
ng author.
sses: akguner@yildiz.edu.tr (C. Akgu¨ner),
edu.tr (M. Kirkit).foundation structures is one of the best solutions when
layers of loose soil overlie bedrock at shallow depths. In
these cases, considerable bearing capacity can be ensured
by the shaft friction in rock, even with small pile displace-
ments (Carrubba, 1997). Piles can be classified based on
the expected governing load-transfer mechanism (CFEM,
2006)(a) at the tip of the pile,
(b) on the pile shaft, or
(c) both at the tip and on the shaft.The axial load carrying capacity of rock-socketed cast-
in-place piles can be estimated by applying static analyses,
information/data collected from pile load tests, numerical
methods and empirical approaches. Load tests are con-
ducted to determine the in situ bearing capacity and the
load–deformation behavior of piles. Pile load testing
provides the most reliable information for the design,
because it is a large-scale, if not full-scale, model for the
behavior of a designed pile in actual soil conditions.
Nomenclature
A,B coefficients of bearing capacity
Ap cross-sectional area of pile
C1 slope of straight line for Chin-Kondner,
Decourt and Tolosko methods
C2 value intersects vertical axis for Chin-Kondner,
Decourt and Tolosko methods
D pile diameter (m)
D displacement (mm)
Dmax displacement value at maximum applied test
load (mm)
Ds limiting displacement for end bearing
resistance (mm)
E modulus of elasticity of pile (MPa)
GWL ground water level
L pile length (m)
Ls socket length (m)
qmax unit bearing resistance at base of pile (MPa)
PL
n net limit pressure (PLP0) in pressuremeter
testing (MPa)
Qmax maximum load applied in pile load test (MN)
Q applied load in pile load test (MN)
Q1 bearing capacity calculated by pile load
test (MN)
Q2 bearing capacity calculated by empirical corre-
lations (MN)
Qfs load at commencement of slip on pile side
Qs load carried on pile side
Qu bearing capacity of pile (MN)
RQD rock quality designation
S parameter in Davisson’s method, elastic dis-
placement of pile
S1 slope of elastic region for load–displacement
curve
S2 slope of total load versus displacement curve
sc unconfined compressive strength of rock (MPa)
SPTN measured penetration number
TCR total core recovery
tmax unit bearing resistance at skin of pile (MPa)
X parameter for Davisson’s method
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–6860In this paper, seven pile load tests, carried out on
socketed cast-in-place (bored) piles within a database of
pile load tests from Turkey (Kirkit, 2009), are investigated
in terms of the axial bearing capacity using load test results
and empirical approaches.2. Properties of pile load tests
All of the studied axial pile load tests were conducted
according to the slowly maintained loading procedure
(ASTM D 1143/D 1143M-07, 2007) and none of them
was loaded to failure. Tests were carried out in three cities
in Turkey, namely, Istanbul, Ankara and Mersin. The
unconfined compressive strength of weathered or fractured
rock near the ground surface obtained through laboratory
tests is usually not reflective of the situation in the whole
rock mass. The unconfined compressive strength of rock
for all sockets is measured by pressuremeter tests (ASTM
D 4719, 2007) conducted during the soil investigationTable 1
Data of pile load tests.
Test
no.
City Rock type D
(m)
L
(m)
Ls
(m)
Ls/
L
sc
(MPa)
Qmax
(MN)
Dmax
(mm)
TP-1 Ankara Marl 0.80 10.0 1.5 0.15 1.6 5.5 42.10
TP-2 Ankara Phyllite 1.65 42.0 6.0 0.15 1.7 12.0 3.53
TP-3 Ankara Schist 0.80 15.0 11.0 0.70 2.2 8.8 13.75
TP-4 Ankara Schist 0.80 20.0 16.0 0.80 2.2 5.9 3.32
TP-5 _Istanbul Graywacke 0.80 11.2 2.2 0.20 0.8 6.0 6.02
TP-6 _Istanbul Graywacke 0.80 11.2 6.4 0.60 0.9 6.0 3.05
TP-7 Mersin Claystone 0.90 20.0 8.5 0.40 1.1 7.0 9.10phase using the method proposed for cohesive soil and
weathered rock by Baguelin et al. (1978). The undrained
shear strength of rock is calculated with Eq. (1), which is
multiplied by two to obtain the unconfined compressive
strength. Np in Eq. (1) is suggested to vary between five
and twelve. A value of 5.5 was used in this study in
accordance with typical Turkish practices. Rotary auger
drilling was used for constructing all of the piles. Test pile
TP-2 is 42 m long and passes through a clayey sand layer
that is 36 m thick. Therefore, bentonite was used to
stabilize the walls of the bored layers during the pro-
duction of TP-2. Pile diameters and lengths, socket
lengths and rock types are summarized in Table 1.
Load–displacement curves for the pile load tests and the
site conditions are presented in Figs. 1–7. PL
n in the figuresFig. 1. Load–displacement curve of TP-1.
Fig. 2. Load–displacement curve of TP-2.
Fig. 3. Load–displacement curve of TP-3.
Fig. 4. Load–displacement curve of TP-4.
Fig. 5. Load–displacement curve of TP-5.
Fig. 6. Load–displacement curve of TP-6.
Fig. 7. Load–displacement curve of TP-7.
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–68 61represents the net limit pressure in the pressuremeter tests:
cu ¼
PLP0
Np
ð1ÞThe load–displacement curves obtained from all the pile
load tests and the empirical methods proposed in the
literature were used for the analysis and the comparison.
The mathematically based graphical methods by Chin-
Kondner (1970), Decourt (1999) and Tolosko (1999) are
Table 2
Bearing capacities of socketed piles.
Test no. Bearing capacity Qu (MN)
Chin-Kondner (1970) Decourt (1999) Tolosko (1999)
TP-1 6.0 6.1 6.2
TP-2 14.7 14.1 14.7
TP-3 11.5 12.1 11.5
TP-4 8.5 11.7 8.6
TP-5 7.8 7.1 7.8
TP-6 10.5 11.0 10.4
TP-7 13.7 13.2 13.7
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–6862used to analyze the bearing capacity obtained from the pile
load tests which have not reached the failure load.
The side friction within the socket of a pile must be
mobilized before base resistance can develop. In the
literature, some limit displacement values for side mobili-
zation have been suggested. In addition, the limit of the
side capacity mobilization of a pile can be evaluated by
utilizing the load–displacement curve obtained from the
pile load tests.
The bearing capacity of rock-socketed piles is calculated
with various empirical correlations, which typically are
obtained by a back analysis of the pile load tests. In these
correlations, the unconfined compressive strength (sc) of
rock is the most commonly considered parameter.3. Interpretation of pile load tests
Many approaches have been proposed in the literature
to determine the bearing capacity of piles using the results
of pile load tests. Mathematically based graphical con-
structions are typically preferred for socketed piles, which
commonly displace a small amount due to several reasons,
such as pile testing conducted for verification, inadequate
loading capabilities and incorrect estimates of the soil
properties.
Chin (1970), using the general correlation for the stress–
deformation behavior of Kondner, proposed a graphical
method to determine the bearing capacity of piles that
were not loaded to failure. In this method, a curve is
drawn from the pile load tests results for which the
x-axis is the pile head displacement ‘‘D’’ and the y-axis is
the pile head displacement divided by the applied load ‘‘D/
Q’’. A straight line is passed from a selected set of points
that occur in the graph. The first few points may be
scattered due to the elastic displacement of the pile or the
displacements within the loading mechanism. This part is
omitted in the estimation of the pile capacity. In the graph,
C1 is the slope of the straight line and C2 is where the
straight line intersects the vertical axis. The pile bearing
capacity is the inverse of the slope of the straight line,
namely
Qu ¼
1
C1
ð2Þ
Decourt (1999) suggested a method similar to the Chin-
Kondner method. In this method, the load ‘‘Q’’ (x-axis)
versus load over displacement ‘‘Q/D’’ (y-axis) graph is
drawn using the results of pile load tests. A linear line is
established from the set of points. The initial points
are not taken into consideration, which is similar to
Chin-Kondner’s method. C1 is the slope of the linear line
and C2 is the value that intersects the vertical axis.
According to this method, the bearing capacity of the pile
is calculated as
Qu ¼ C2
C1
ð3ÞFor piles not loaded to failure, Tolosko (1999) offered a
new method combining the Chin-Kondner and Davisson
methods. In this method, the bearing capacity of a pile
(Qu) is
Qu ¼
½ðC1XþC2SÞ7
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ðC1XþC2SÞ2
q
þ4C1XS
ð2C1SÞ
ð4Þ
‘‘C1’’ and ‘‘C2’’ in Eq. (4) are the values obtained from
Chin-Kondner’s method. In Eqs. (5)and (6), ‘‘X’’ and ‘‘S’’
are the values obtained from Davisson’s (1972) method
based on the parameters of the pile:
X ¼ 4þ D
120
ð5Þ
S¼ L
EAp
ð6Þ
D and L are the diameter and the length, respectively, E is
Young’s modulus and Ap is the cross-sectional area.
3.1. Bearing capacities from investigated pile load tests
The axial capacities, based on the pile load tests
conducted on socketed cast-in-place piles, are obtained
by the above-described graphical methods and are sum-
marized in Table 2. It is noticeable that, with the exception
of Decourt’s approach for TP-4, the results from all of the
methods vary by only a small amount.
Additionally, the Davisson (1972), De Beer (1967),
Fellenius (1980) and Van der Veen (1953) methods were
also considered in the calculations. However, these meth-
ods were not useful for obtaining the bearing capacity of
the analyzed rock-socketed piles. In Davisson’s method,
the applied load (Q) was large and the corresponding
displacement (D) was very small, i.e., well below the
defined limit displacement value. Likewise, NeSmith and
Siegel (2009) found Davisson’s method to be overly
conservative in evaluating the cast-in-place piles and
questioned its practical appropriateness in such cases.
The bearing capacities calculated by De Beer’s method
were too low, and no unique bearing capacity could be
obtained by Van Der Veen’s method.
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–68 634. Load transfer mechanism of socketed piles
Three of the considered test piles (TP-1, TP-2 and TP-7)
were socketed into strong rock layers underlying much
weaker soil layers, while the rest of the piles (TP-3, TP-4,
TP-5 and TP-6) were penetrated through weathered rock
before reaching competent rock layers. In accordance with
the common practical approach (CFEM, 2006; Das, 2011),
any possible influence from the layers above the socketed
surfaces to the axial capacity is disregarded in this paper
due to the typically large differences in rigidity between
sockets and overlying layers as well as redundancy.Fig. 8. Schematic interpretation of socketed pile test.
Fig. 9. Comparison of tests bThe idealized load–displacement behavior of a rock-
socketed pile may be assumed as in Fig. 8 (Carter and
Kulhawy, 1988), where S1 is the slope of the elastic region
and S2 indicates the slope of the total carried load. The
intersection of these two slopes corresponds to the com-
mencement of slip on the pile skin (Qfs).
It is generally accepted that a significant portion of the
applied loads on the socketed piles are transferred to the
rock–pile interface at the side, since frictional side resis-
tance commonly mobilizes at small relative displacements
between the rock and the pile. Slippage occurs after the
displacement on the pile side exceeds the threshold value,
after which the pile base capacity is mobilized. Conse-
quently, within working loads, the load carried on the base
of a pile may be only as much 10% to 20% of the applied
load on the pile head (Williams et al., 1980; Carter and
Kulhawy, 1988), whereas Crapps and Schmertmann (2002)
concluded that the same amount may increase to an
average of 30% based on Osterberg load tests. There are
many parameters that affect the distribution of loads
carried on the side and base of a vertically loaded pile,
such as the normal stress on the socket, the strength and
quality of the concrete in the shaft and base of the pile, the
amount of loosened material and construction debris
below the base, the drilling shape and equipment (hand/
auger/core), the pile diameter, the pile length, the rock type
and the groundwater (Rosenberg and Journeaux, 1976;
Carrubba, 1997; Pells, 1999; Nam and Vipulanandan,
2008). Among these, surface roughness was found to be
the single most important unknown parameter for side
friction by Johnston and Lam (1989) and Seidel and
Collingwood (2001).
Furthermore, several limit displacements are suggested
to fully mobilize the side capacity derived from the results
of the pile load tests conducted on socketed piles. Horvath
(1982) indicated that large-scale socketed cast-in-placeeyond the elastic region.
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–6864piles should undergo an average relative displacement of
5.0 mm, whereas Rosenberg and Journeaux (1976) sug-
gested a limit value of 6.35 mm (0.25 in.). NCHRP (2006)
found that the side resistance typically reaches a maximum
displacement in the range of 5–10 mm. Additionally, for
socketed piles installed in Turkey, the entire load is, albeit
conservatively, assumed to be carried solely by the side
friction when the displacement is less than 10 mm
(Yıldırım, 2009). Similarly, in the Mumbai Region of
India, where weathered rock such as basalt, breccia and
tuff are common, Basarkar and Dewaikar (2006)Table 3
Relationship between Ds, D and L.
Test no. Ds (mm) Ds/D (%) Ds/L (%)
TP-1 4.2 5.25 0.42
TP-3 6.6 8.25 0.44
TP-5 3.0 3.75 0.27
Table 4
‘‘A’’ and ‘‘B’’ values for side shear resistance.
Method A B
Rosenberg and Journeaux (1976) 0.375 0.515
Rowe and Armitage (1987) 0.45 0.5
Rowe and Armitage (1987) 0.6 0.5
Horvath et al. (1983) 0.2–0.3 1
Meigh and Wolski (1979) 0.22 0.6
Gupton and Logan (1984) 0.2 1
Reynolds and Kaderabek (1980) 0.3 1
Toh et al. (1989) 0.25 1
Carter and Kulhawy (1988) 0.2 0.5
Zhang and Einstein (1998) 0.4 0.5
Zhang and Einstein (1998) 0.8 0.5
Fig. 10. Empirical methodscalculated a ‘‘critical’’ displacement value of 10 mm to
mobilize the maximum side shear.
Four of the seven load tests considered in this study (TP-
1, TP-3, TP-5 and TP-7) exceeded 5 mm. No significant
break point could be located for TP-7. For TP-1, TP-3 and
TP-5, the limit displacements, where slippage is assumed to
occur, were obtained from pile load test results, as
suggested by Carter and Kulhawy (1988) (Fig. 9). Due to
the large variability, it is not possible to recommend a
single limiting displacement for the commencement of the
base resistance. The ratios of the limiting displacement (Ds)
to the pile diameter (D) and the length (L) are given in
Table 3.
5. Empirical methods
Empirical methods generally suggest separate side and
base resistance correlations, although there is also an
analytical approach that incorporates the soil coupling
effect (Seol et al., 2009). The approaches proposed by
various researchers can be generalized, as in Eq. (7), whereDescription Reference
Rosenberg and Journeaux (1976)
R1, R2 and R3 rough sockets Rowe and Armitage (1987)
R4 rough sockets Rowe and Armitage (1987)
A¼0.25 (average) Horvath et al. (1983)
Zhang (2004)
Zhang (2004)
Zhang (2004)
Zhang (2004)
Carter and Kulhawy (1988)
Smooth socket Zhang and Einstein (1998)
Rough socket Zhang and Einstein (1998)
for side shear resistance.
Table 5
Roughness factor for side capacity analysis (Pells et al., 1980).
Roughness class Description
R1 Straight, smooth-sided socket, grooves or indentation less than 1.00 mm deep
R2 Grooves of depth 1–4 mm, width greater than 2 mm, at spacing 50–200 mm
R3 Grooves of depth 4–10 mm, width greater than 5 mm, at spacing 50–200 mm
R4 Grooves or undulations of depth greater than 10 mm, width greater than 10 mm, at spacing 50–200 mm
Table 6
Methods for end bearing capacity (qmax) and ‘‘A’’ and ‘‘B’’ values in Eq. (6).
Method A B Description Reference
Coates (1967) 3 1 Zhang (2008)
Rowe and Armitage (1987) 2.7 1 Rowe and Armitage (1987)
Argema (1992) 4.5 1 qmaxr10 MPa Zhang (2008)
Nam (2004) 2.14 0.66 3 pile load tests Nam (2004)
Vipulanandan et al. (2007) 4.66 0.56 21 pile load tests Vipulanandan et al. (2007)
Zhang (2008) 4.93 0.5 50 pile load tests Zhang (2008)
Fig. 11. Empirical methods for end bearing capacity.
Table 7
Side shear resistances of studied socketed piles.
Test
no.
sc
(MPa)
Side shear resistance of socket (MPa)
Rosenberg and
Journeaux (1976)
Rowe and
Armitage
(1987)
Horvath
et al.
(1983)
Meigh and
Wolski,
(1979)
Gupton and
Logan (1984)
Reynolds and
Kaderabek
(1980)
Toh
et al.
(1989)
Carter and
Kulhawy
(1988)
Zhang and
Einstein
(1998)
TP-1 1.6 0.48 0.57 0.40 0.29 0.32 0.48 0.40 0.25 0.51
TP-2 1.7 0.49 0.59 0.43 0.30 0.34 0.51 0.43 0.26 0.52
TP-3 2.2 0.56 0.67 0.55 0.35 0.44 0.66 0.55 0.30 0.59
TP-4 2.2 0.56 0.67 0.55 0.35 0.44 0.66 0.55 0.30 0.59
TP-5 0.8 0.33 0.40 0.20 0.19 0.16 0.24 0.20 0.18 0.36
TP-6 0.9 0.36 0.43 0.23 0.21 0.18 0.27 0.23 0.19 0.38
TP-7 1.1 0.39 0.47 0.28 0.23 0.22 0.33 0.28 0.21 0.42
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–68 65
Table 8
End bearing capacities of investigated socketed piles.
Test
no.
sc
(MPa)
End bearing capacity of socket (MPa)
Coates
(1967)
Rowe and
Armitage
(1987)
Argema
(1992)
Nam
(2004)
Vipulanandan
et al. (2007)
Zhang
(2008)
TP-1 1.6 4.80 4.32 7.20 2.92 6.06 6.24
TP-2 1.7 5.10 4.59 7.65 3.04 6.27 6.43
TP-3 2.2 6.60 5.94 9.90 3.60 7.25 7.31
TP-4 2.2 6.60 5.94 9.90 3.60 7.25 7.31
TP-5 0.8 2.40 2.16 3.60 1.85 4.11 4.41
TP-6 0.9 2.70 2.43 4.05 2.00 4.39 4.68
TP-7 1.1 3.30 2.97 4.95 2.28 4.92 5.17
Table 9
Bearing capacities of socketed piles—graphical versus empirical
approaches.
Test no. Qu (MN) Q1/Q2
Graphical estimation, Q1 Empirical correlation, Q2
TP-1 6.0 5.0 1.2
TP-2 14.7 16.2 0.9
TP-3 11.5 20.1 0.6
TP-4 8.5 23.8 0.4
TP-5 7.8 4.2 1.9
TP-6 10.5 6.1 1.7
TP-7 13.7 10.1 1.4
Fig. 12. Comparison of estimated bearing capacities.
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–6866qmax is the base resistance (MPa), tmax is the skin resistance
(MPa) and A and B are the bearing capacity coefficients
(unitless):
qmax ; tmax ¼AðscÞB ð7Þ
The A and B values in Eq. (6), applied to calculate the side
resistance of a rock-socketed pile, are listed in Table 4 and
compared in Fig. 10. The correlation by Rowe and
Armitage (1987) uses the roughness categories of rock
(Table 5) by Pells et al. (1980).
The unconfined compressive strength of rock in units of
MPa is the main parameter utilized in these correlations.
The proposed correlations for the base resistance are given
in Table 6 and compared in Fig. 11.
5.1. Empirical analysis of socketed piles
The side resistance and the base resistance of the studied
socketed cast-in-place piles, estimated by the empirical
methods, are listed in Tables 7 and 8, respectively. The
socket wall roughness varies based on the method used in
construction as well as on the strength and the joints of the
rock. Sockets may be excavated by hand, producing a very
rough socket wall, whereas more typical methods, such as
rotary augers and corers, present a relatively smooth socket
(Williams and Pells, 1981; Nam and Vipulanandan, 2008).
Since the roughness of the sockets was not measured and
rotary augers were used in the construction of the sockets,
the unit side resistance suggested by Rowe and Armitage
(1987) was used with roughness values R1, R2 and R3
(relatively smooth sockets). Similarly, the socket is assumed
to be smooth for the correlation suggested by Zhang and
Einstein (1998).
6. Comparison of bearing capacities—load tests versus
empirical methods
6.1. Measured bearing capacities by pile load tests (Q1)
The precise cast-in-place pile bearing capacities from load
tests are not known since none reached the failure load. The
bearing capacities calculated by all of the graphical methodswere similar. For convenience, therefore, the estimates
obtained from the Chin-Kondner (1970) approach were
selected for comparison.
6.2. Calculated capacities with empirical methods (Q2)
The correlations by Zhang and Einstein (1998) and
Zhang (2008) are selected for the side resistance and the
base resistance, respectively, to calculate Q2, due to their
nonlinearity, their estimates within a narrow range and
their approximately average results within other consid-
ered correlations.
Only side resistance values are calculated for load tests
TP-2, TP-4, TP-6 and TP-7, since recorded displacements
are less than those necessary for side shear mobilization, in
accordance with Carter and Kulhawy (1988). Loads are
carried at both the side and the base of piles TP-1, TP-3
and TP-5.
The bearing capacities of the piles calculated by load
tests (‘‘graphical’’ using Chin-Kondner’s construction) and
by ‘‘empirical’’ correlations are summarized in Table 9 and
compared in Fig. 12. Q1/Q2 ratios vary from 0.4 to 1.9 with
an average of 1.1. The bearing capacities obtained from a
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–68 67graphical evaluation of the load test measurements are less
than those calculated with the empirical correlations when
the calculated values are larger than 10 MN. In contrast,
the opposite is valid for calculated values less than 10 MN.
7. Conclusions
The following conclusions can be drawn from this
study to estimate the bearing capacity of rock-socketed
cast-in-place piles based on an evaluation of the empirical
correlations utilizing the unconfined compressive strength
of rock and approaches that directly employ pile load
tests:– There is a multitude of suggested methods to determine
the bearing capacity of piles through data collected
from load testing, most of which were utilized for this
research. Very close and acceptable results were
obtained by the Chin-Kondner, Decourt, and Tolosko
approaches. Since none of the tested piles were loaded
to failure, it can be concluded that any of these three
evaluations can be reasonably used to determine the
bearing capacity of socketed piles subjected to such load
tests. However, all of the suggested methods are
sensitive to the selection of points in the graphical
construction. The first few deviating data can be
attributed to errors, such as small deformations in the
loading frame, and the seating of the testing equipment,
which may be ignored.– In this study, a comparison is conducted of the axial pile
bearing capacities from load tests and empirical correla-
tions. While some results were very close to each other
(TP-1 and TP-2), others varied significantly (TP-4 and
TP-5). Nevertheless, the bearing capacities obtained by
the direct (graphical) interpretation of load tests on
rock-socketed cast-in-place piles and empirical correla-
tions, suggested in the literature, are within the accep-
table limits of each other if the unconfined compressive
strength of rock can be estimated within satisfactory
accuracy of the actual field conditions. Thus, empiri-
cism, sample disturbance, difficulties in representing the
samplings of rock and the determination of socket
roughness can be expected to be the main sources of
error when estimating the axial pile capacity through
empirical correlations.– The suggestions in the literature of a specific limiting
displacement, after which the applied axial load is
shared between the side resistance and the base resis-
tance of a rock-socketed cast-in-place pile, are not
supported by the scatter observed in the data obtained
in this study.– The approach suggested by Carter and Kulhawy (1988)
may be used to reasonably determine the limiting
displacement to mobilize the pile base resistance if data
from load tests are available.– Although an approximate ratio of the limiting displace-
ment over the pile length of% 0.4 is found in this study,it should be investigated further for validity.
– In the absence of pile load tests, axial capacity estimates
of rock-socketed cast-in-place piles should be made by
assuming that only the side resistance has mobilized,
which will likely lead to conservative outcomes.Acknowledgments
The authors wish to acknowledge Professor Dr. Kutay
O¨zaydın, Professor Dr. Mustafa Yıldırım, Professor
Dr. So¨nmez Yıldırım, Professor Dr. Turan Durgunog˘lu,
Turhan Karadayılar and Dr. Og˘uz C- alıs-an for their
valuable contributions in preparing this paper.References
Argema, 1992. Design guides for offshore structures: offshore pile design.
In: Tirand, P.L. (Ed.), Edition Technip, Paris, France.
Basarkar, S.S., Dewaikar, D.M., 2006. Load transfer characteristics of
socketed piles in Mumbai region. Soils and Foundations (Japanese
Geotechnical Society) 46 (2), 247–257.
Baguelin, F., Jezequel, J.F., Shields, D.H., 1978. The Pressuremeter and
Foundation Engineering. Trans-Tech Publication.
Canadian Geotechnical Society, 2006. Canadian Foundation Engineering
Manual, 4th edition Bitech Publishers Ltd., Vancouver, BC.
Carrubba, P., 1997. Skin friction of large-diameter piles socketed into
rock. Canadian Geotehnical Journal, Ottawa Canada 34, 230–240.
Carter, J.P., Kulhawy, F.H., 1988. Analysis and Design of Drilled Shaft
Foundations Socketed into Rock. EPRI EL-5918. Ithaca, New York.
Chin, F.K., 1970. Estimation of the ultimate load of pile not carried to
failure. In: Proceedings of the Second Southeast Asian Conference on
Soil Engineering, Singapore, pp. 81–90.
Coates, D.F., 1967. Rock mechanics principles. Energy Mines and Resources,
Ottawa, Canada, Monograph, p. 874.
Crapps, D.K., Schmertmann, J.H., 2002. Compression top load reaching
shaft bottom—theory versus tests. In: O’Neill, M.W., Townsend, F.C.
(Eds.), Proceedings of the International Deep Foundations Congress,
Orlando, FL, 14–16 February 2002. Geotechnical Special Publication
No. 116, vol. 2. Geo-Institute, American Society of Civil Engineers,
Reston, VA, pp. 1533–1549.
D 1143/D 1143M-07 (ASTM), 2007M. Standard Test Method for Piles
Under Static Axial Compressive Load. American Society for Testing
and Materials, United States.
D 4719-07 (ASTM), 2007. Standard Test Method for Prebored Pressure-
meter Testing in Soils. American Society for Testing and Materials,
United States.
Das, B.M., 2011. Principles of foundation engineering, seventh ed. Cengage
Learning, USA.
Davisson, M.T., 1972. High Capacity Piles,. Proceedings of Lecture Series
on Innovations in Foundation Construction, American Society of
Civil Engineers, ASCE, Illinois Section, Chicago, 81–112.
Decourt, L., 1999. Behavior of foundations under working load conditions.
In: Proceedings of the 11th Pan-American Conference on Soil Mechanics
and Geotechnical Engineering, Foz Dulguassu, Brazil, vol. 4, pp. 453–488.
De Beer, E.E., 1967. Proefondervindlijke bijdrage tot de studie van het
grensdraag vermogen van zandonder funderingen op staal. Tijdshift
der Openbar Verken van Belgie, No. 6.
Fellenius, B.H., 1980. The analysis of results from routine pile load tests.
Ground Engineering, London 13, 19–31.
C. Akgu¨ner, M. Kirkit / Soils and Foundations 52 (2012) 59–6868Gupton, C., Logan, T., 1984. Design guidelines for drilled shafts in weak
rocks of South Florida. In: Proceeding South Florida Annual ASCE
Meeting. ASCE.
Horvath, R.G., 1982. Behavior of Rock-Socketed Drilled Pier Founda-
tions. Ph.D. Thesis. University of Toronto, Toronto.
Horvath, R.G., Kenney, T.C., Kozicki, P., 1983. Methods of improving
the performance of drilled piers in weak rock. Canadian Geotechnical
Journal, Ottawa, Canada 20 (4), 758–772.
Johnston, I.W., Lam, T.S.K., 1989. Shear behavior of regular triangular
concrete/rock joints—analysis. Journal of Geotechnical Engineering,
ASCE 115 (5), 711–727.
Kirkit, M., 2009. Establishing a Data Base of Pile Load Tests Conducted
in Turkey and Analysis of Rock-Socketed Piles within Data Base.
Master Thesis. Yıldız Technical University, Institute of Science,
_Istanbul (in Turkish).
Meigh, A.C., Wolski, W., 1979. Design parameters for weak rocks. In:
Proceeding of the seventh European Conference on Soil Mechanics
and Foundation Engineering, vol. 5. British Geotechnical Society,
Brighton, pp. 59–79.
Nam, M.S., 2004. Improved Design for Drilled Shafts in Rock. Ph.D.
Thesis. University of Houston, Houston, TX.
Nam, M.S., Vipulanandan, C., 2008. Roughness and unit side resistances of
drilled shafts socketed in clay shale and limestone. Journal of Geotech-
nical and Geoenvironmental Engineering (ASCE) 134 (9), 1272–1279.
NCHRP Transportation Research Board, 2006. NCHRP SYNTHESIS
360 Rock-Socketed Shafts for Highway Structure Foundations.
NCHRP, Washington.
NeSmith, W.M., Siegel, T.C., 2009. Shortcomings of the Davisson offset
limit applied to axial compressive load tests on cast-in-place piles. In:
Contemporary Topics in Deep Foundations—Geotechnical Special
Publications No. 185. ASCE, pp. 568–574.
Pells, P.J.N., 1999. State of practice for the design of socketed piles in rock.
In: Proceedings of the Eighth Australia New Zealand Conference on
Geomechanics. Australian Geomechanics Society, pp. 307–327.
Pells, P.J.N., Rowe, R.K., Turner, R.M., 1980. An experimental investi-
gation into side shear for socketed piles in sandstone. Proceedings of
the International Conference on Structural Foundations on Rock,
Sydney, Australia 1, 291–302.
Reynolds, R.T., Kaderabek, T.J., 1980. Miami limestone foundation
design and construction. ASCE, New York.
Rosenberg, P., Journeaux, N.L., 1976. Friction and end bearing tests on
bedrock for high capacity socket design. Canadian Geotechnical
Journal, Ottawa, Canada 13, 324–333.Rowe, R.K., Armitage, H.H., 1987. A design method for drilled piers in soft
rock. Canadian Geotechnical Journal, Ottawa, Canada 24 (1), 126–142.
Seidel, J.P., Collingwood, B., 2001. A new socket roughness factor for
prediction of rock socket shaft resistance. Canadian Geotechnical
Journal, Ottawa, Canada 38, 138–153.
Seol, H., Jeong, S., Cho, S., 2009. Analytical method for load-transfer
characteristics of rock-socketed drilled shafts. Journal of Geo-
technical and Geoenvironmental Engineering (ASCE) 135 (6),
778–789.
Toh, C.T., Ooi, T.A., Chiu, H.K., Chee, S.K., Ting, W.N., 1989. Design
parameters for bored piles in a weathered sedimentary formation. In:
Proceeding 12th International Conference on Soil Mechanics and
Foundation Engineering, Rio de Janerio 2, 1073–1078.
Tolosko, T.A., 1999. Extrapolation of Pile Capacity from Non-Failed
Load Tests. Master of Science in Civil Engineering. University of
Massachusetts, Lowell.
Van der Veen, C., 1953. The bearing capacity of pile. In: Proceedings of
the Third ICSMFE, pp. 84–90.
Vipulanandan, C., Hussain, A., Usluogulari, O., 2007. Parametric study
of open core-hole on the behavior of drilled shafts socketed in soft
rock. In: Proceedings of the Geo-Denver 2007, Geotechnical Special
Publication No. 158. Contemporary Issues in Deep Foundations,
Denver, Colorado, in Cd-Ram.
Williams, A.F., Johnston, I.W., Donald, I.B., 1980. The design of
socketed piles in weak rock. In: Proceedings of the International
Conference on Structural Foundations on Rock, Balkema, Sydney,
Australia, pp. 327–347.
Williams, A.F., Pells, P.J.N., 1981. Side resistance of rock sockets in
sandstone, mudstone and shale. Canadian Geotechnical Journal,
Ottawa, Canada 18, 502–513.
Yıldırım, S., 2009. Site Investigations and Foundation Design. Birsen
Yayınevi, _Istanbul (in Turkish).
Zhang, L., 2004. Drilled Shafts in Rock. A.A. Balkema Publishers, Leiden.
Zhang, L., 2008. Predicting the end bearing capacity of rock socketed
shafts. In: Proceedings of the Third Annual & 11th International
Conference on Deep Foundations, October 15–17, Deep Foundations
Institute, New York, USA, pp. 307–316.
Zhang, L., Einstein, H.H., 1998. End bearing resistance of drilled shafts in
rock. Journal of Geotechnical and Geoenvironmental Engineering
(ASCE) 124 (7), 574–584.