JOURNAL OF INFORMATION, KNOWLEDGE AND RESEARCH IN
CIVIL ENGINEERING
RECENT STUDIES ON PILED-RAFT FOUNDATION:
STATE OF ART
1V.J.SHARMA, 2
1, 2, 3 Applied
S.A.VASANVALA, 3C.H.SOLANKI
Mechanics Department, Sardar Vallabhai National Institute of
Technology, Ichchhanath, Surat-7, Gujarat,India.
nitk.vijay@gmail.com
ABSTRACT : Due to increase of civilization in recent decades the demand of land for construction purpose has
increased exponentially. As most of the time site available consists of weak subsoil conditions, piled raft
foundation has been preferred on large scale due its efficiency of carrying high vertical loads within the
permissible settlement limits and cost effectiveness compared to pile foundation system. This paper presents the
brief review of various studies on piled-raft foundation in last decade. The paper also reveals latest modification
done in conventional piled-raft as per site conditions and loading criteria.
Keywords: Differential Settlement, Total Settlement, Finite Element Method, Non-Identical Piles, Composite
Piled-Raft, Viscohypoplastic
1. INTRODUCTION
In traditional foundation design, it was customary to
consider first the use of shallow foundation such as a
raft (possibly after some ground-improvement
methodology performed). If it was not adequate, deep
foundation such as a fully piled foundation was used
instead. In the former, it was assumed that load of
superstructure was transmitted to the underlying
ground directly by the raft. In the latter, the entire
design loads were assumed to be carried by the piles
[24].In recent decades, another alternative
intermediate between shallow and deep foundation,
what is called piled raft foundation or settlement
reducing piles foundation, has been recognized by
civil engineers. The piled raft concept has been used
extensively in Europe and Asia. In this concept, piles
are provided to control settlement rather than carry
the entire load. Piled raft foundation has been proved
to be an economical way to improve the
serviceability of foundation performance by reducing
settlement to acceptable levels. The favorable
application of piled raft occurs when the raft has
adequate loading capacities, but the settlement or
differential settlement exceed allowable values.
Conversely, the unfavorable situations for piled raft
include soil profiles containing soft clays near the
surface, soft compressible layers at relatively shallow
depths and some others [24]. In the unfavorable
cases, the raft might not be able to provide significant
loading capacity, or long-term settlement of the
compressible underlying layers might reduce the
contribution of raft to the long-term stiffness of
foundation. As we know piled-raft foundation system
is applied in weak subsoil conditions where chances
of foundation settlement play vital and major role in
design of foundation system. This paper presents
review of various studies carried out on piled-raft
foundation in clayey soil, sandy soil and weathered
rocks. Various researchers have worked on piled–raft
foundation system in clayey soil. Their work includes
study related to bearing behavior, composite system,
non-linear FEM analysis, piled-raft system with nonidentical piles, etc. The Studies related to sandy soil
includes separate analysis of pile and raft, case
studies and use of FEM codes. Few works has been
carried out on weathered rock which includes paper
[3,7,10,and 25].Researcher [7] has carried out work
in sand as well as weathered rock.
2 .REVIEW
The review includes various papers published in
various journals such as American society of civil
engineering, Proceedings of the 17th International
Conference on Soil Mechanics and Geotechnical
Engineering ,Proceedings of ICE , etc .They have
been grouped into major areas as:
1.
Study of pile raft system in clay
2.
Study of pile raft system in sand and
weathered rock
2.1
Study of pile raft system in clay :
In situations where a raft foundation alone does not
satisfy the design requirements, it may be possible to
enhance the performance of the raft by the addition of
piles. The use of a limited number of piles,
strategically located, may improve both the ultimate
load capacity and the settlement and differential
settlement performance of the raft. The study on
design of piled-raft system in clayey soils have been
carried by [25, 15, 32, 31, 27, 28 19, 22 and 12].The
design of piled raft system involves basically bearing
capacity of supporting subsoil and permissible
allowable total and differential settlements. Poulos
H.G. [25] had given outline of simplified method of
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carrying out a preliminary feasibility study and
design of a piled raft system. The analysis is
programmed via a spreadsheet program or a
mathematical program such a MATHCAD. The
approach gives a reasonable estimate of the order of
the magnitude of settlement and differential
settlement of foundation when applied to case study
of piled raft on stiff clay and series of centrifuge tests
on reconstituted soil. Liew S. S etal [15] have
designed and presented instrumentation results of
reinforcement concrete piled raft supporting 2500Ton
oil storage tanks on a very soft alluvial clayey soil of
about 40m thick in Riau Province of Sumatra,
Indonesia. The design concept has been validated
with the results of instrumentation Seo Y.K etal [32]
have proposed design charts of piled raft foundations
on soft clay. The design charts were first presented
for the evaluation of both bearing capacity and total
settlement in the raft alone foundation system. Load
settlement relationship curves are used to evaluate the
ultimate soil bearing capacity. The total settlement is
evaluated by applying various traditional safety
factors of the uniformly distributed loads. Then, the
parametric studies were carried out for the piled raft
foundation system. In the numerical analyses, elastoplastic finite elements models are used to present the
foundation response and the design charts, which
enable the determination of the raft size and pile
length and spacing of piles. Sanctis L.D etal. [31] has
proposed a simple design criterion to evaluate the
ultimate vertical load of a piled raft as a function of
its component capacities, which can be simply
evaluated by the conventional bearing capacity
theories. A broad parametric study is carried out
using 3D FEM analysis to define the failure load
coefficients accounting for the interaction between
the raft and the pile group at failure. Also a guideline
has been given to assess the factor of safety of
vertically loaded piled raft. As per Meisam Rabiebi
[27] the maximum bending moment in raft increases
with increase raft thickness, decrease pile number
and decrease in pile length. Central and differential
settlement decreases with increase raft thickness and
uniform increase in pile length. Further Meisam
Rabiei [28] used a computer program ELPLA and
found that pile configuration and load distribution
are very important and effective in piled raft
settlement , maximum moment and pile bearing
factor. Three basic pile configurations and three load
distribution types were considered. Pile configuration
1 has the pile uniformly distributed under whole raft
area. Pile configuration 2 has piles under central
area of the raft as well as under the edge of the raft.
In pile configuration 3 the piles are placed only in the
central area of the raft, the detail is shown in fig.1 .
Novak L.J etal [19] carried out analysis of pile-raft
foundations with 3D finite-element method .They
found following reasons for use of the 3D Finite
.
Element Method (FEM): (1) the problem is so
complex that simplified methods cannot model the
problem correctly; and (2) codes for the FEM are
available, powerful, and capable of being run on the
personal computer. Comparisons were made between
experimental and analytical results for two piled –raft
foundations resting on stiff clay and the FEM has
shown to yield excellent results for the cases
analyzed .Oh E.Y.N etal. [22] have carried out
numerical analysis of un-piled raft and piled raft on
two different soil conditions. The analysis was
carried out in two case studies with three typical load
intensities of serviceability load. The subsoil was
modeled as linear elastic materials, raft as beam
element and piles as element with shear and normal
coupling springs. For case study 1 with sandy soil
condition maximum settlement of piled raft depends
on piles spacing and number of piles. For case study
2 with clayey subsoil, the settlement of un-piled raft
was similar for different raft thickness .Raft thickness
was found to have obvious effect on differential
settlement. The settlement of piled raft at piled area
showed a bowl shape settlement pattern and edge of
the raft strip showed a downward deviation from
the settlement bowl. Lee J H.etal [12] has conducted
series of 3D elasto-plastic finite element analyses to
investigate the bearing behavior of a square piled raft
subjected to vertical loading. In this study, the main
characteristic of these analyses was to permit soil slip
at the pile–soil interface. Pile positions, pile number,
pile length and loading distributions on the raft were
varied, and the effects of pile–soil slip, pile
geometries and loading types were examined.
Furthermore, the proportion of load sharing of the
raft and piles at the ultimate state and the relationship
between the settlement and overall factor of safety
was evaluated. The results show that the use of a
limited number of piles, strategically located, might
improve both bearing capacity and the settlement
performance of the raft. The work related to piledraft foundation resting on over-consolidated clay was
carried out by [8, 29, 30], which includes numerical
study of piled-raft foundation behavior and
comparison with field measured results. Reul O.etal
[30] carried out
comparisons
of in-situ
measurements and numerical analyses for three
piled raft foundations on over-consolidated clay
between overall settlement , differential settlement
and load carried by piles by back analysis. Three
main performance indicators of the piled raft were
proposed: the proportion of load carried by the
piles,and the maximum settlement and maximum
differential settlement, both as a proportion of the
corresponding
quantity for an unpiled raft
foundation. The last indicator suggests that improved
layout of the pile support can lead to a reduction both
in the maximum differential settlement and in the
overall quantity of piles.
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Figure 1. Model configuration and properties used in the analysis
Garcia F etal [8] had applied viscohypo plastic
model to the case history of piled raft
foundation- Messeturm
tower
in Frankfurt
Germany with 3D FEM analysis with ABAQUS
and the user subroutine UMAT developed by A.
Niemunis and the geotechnical group of the
Karlsruhe university in Germany. The calculated
results are compared with the in situ measurements
with the purpose to verify the viscohypoplastic law
in a boundary value problem. It was found that
viscohypoplastic model can predict with good level
of agreement the behavior of a piled raft
foundation. Reul O. [29] has carried out numerical
study of bearing behavior of piled rafts in
overconsolidated clay. It is shown that the
interaction between piles and rafts is a major
influence on bearing capacity of piled-raft
foundation.
To mobilize shallow soil in coastal areas to
participate in the interaction of piled raft foundation
sufficiently, the researchers extended the concept of
piled raft to a new type of foundation named
composite piled raft. In the system of composite
piled raft, the short piles made of flexible materials
were used to strengthen the shallow soft soil, while
the long piles made of relatively rigid materials
were used to reduce the settlements and the cushion
beneath the raft was used to redistribute and adjust
the stress ratio of piles to subsoil. Researchers [13,
41, 14, 40] had carried out rigorous analysis on
CPRF system .Liang F.Y. etal [13] have carried out
numerical analysis of composite piled raft with
cushion subjected to vertical load. Influencing
factors such as ratio of length to diameter and
elastic moduli of piles as well as thickness and
elastic modulus of cushion were studied in details.
Load-sharing ratios of piles and subsoil as well as
foundation settlement were also investigated.
Zheng J.J. etal [41] carried out 3D non-linear finite
element modeling of composite foundation formed
by Cement-Flyash-Gravel-lime piles which is a
widely used ground improvement technique. A
CFG–lime multi-pile composite foundation is a
new concept utilizing CFG and lime piles as shown
in fig 2. The parameters studied include the length
and diameter of piles and the thickness of the
cushion. The stress distribution beneath the
composite foundation, the influence of the cushion
on load-settlement behavior, and the ratio of
stresses in the piles to those in the subsoil are also
studied. The results show that settlement is much
more significantly affected by the length and
diameter of the CFG pile rather than that of the
lime pile, thus CFG pile acts as a settlement-
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reducing pile. On the other hand, the load
distribution between piles and subsoil is
significantly affected by the cushion thickness.
Optimization of composite piled raft foundation
with varied rigidity of cushion was carried out by
Liang F.etal [14 ].The analysis model of piled raft
foundation was set up using the fictitious pile
method , and Fredholm’s integral equations of the
second kind were deduced to solve the problems
.By simulating the cushion with wrinkle springs ,
the effect of cushion was taken into consideration.
The method is suitable to analyze the foundation
under working loads and could be applied to solve
problems of different rigidities of piles and cushion.
ZHAO M.H.etal [40 ] have carried out settlement
calculation for long –short composite piled raft
foundation.Based on the shear deformation
method,the Mylonakis and gazetas model was
introduced . Considering the effects of cushion ,
the
flexible
factors
of interaction
were
provided.Then the settlement calculation for
long-short composite piled raft foundation was
developed. The non-linear analyses of piled-raft
foundation have been interesting area of study for
many researchers which include [16, 17, 37, 33,
and 4].Maharaj D.K etal [16] worked on non-linear
finite element analysis of piled –raft foundation
resting on clay soil layers .. In this study the raft
and piles are assumed to be linearly elastic and
Drucker-Prager criterion has been used to represent
soil as elasto-plastic material.Based on threedimensional non-linear finite element analysis, it
was found that the addition of even a small number
of piles increases the load-carrying capacity of a
raft foundation. The axial load distribution shows
that the piles reach their ultimate capacity earlier
than the raft. Maharaj D.K. [17 ] continued his
work in non-linear finite element analysis of piled
raft foundation under the application of uniformly
distributed load .Fig 3 shown below gives finite
element discretization and boundary conditions
applied to pile raft foundation. Load settlement
curves of raft and piled raft foundation have been
provided for different raft and pile stiffness.
Vásquez L.G etal [37] had carried out non-linear
three-dimensional finite element analysis to
estimate capacity of piled raft.
Figure 2. Sketch of CFG –lime pile composite
foundation
Figure 3. Finite element discretization for piledraft
A windows based general-purpose finite element
program (AMPS) was used to carry out the
analyses.A suitable nonlinear model is used to
model the soil behavior ,and contact interfaces are
included to study the interaction between soil and
piles and between soil and slab .Two piled-raft
system were analyzed. It was found that the
contribution of the pile tip in the resistance tends to
increase as the deformation increases.Non-linear
finite element analysis of piled-raft foundation
resting on layers of soil having different stiffness
have been done by [33,4,5]. Small J.C.etal [33] has
developed a method of analysis for piled raft
foundation where piles exhibits nonlinear load –
deflection behavior. The raft is analysed by finite
element methods, while the piles are treated as
springs having a variable stiffness,so as to model
any non-linear behaviour. The soil is treated as an
elastic medium that may consist of layers of soil
having different stiffnesses. The method has been
incorporated into the computer program GARP
(General Analysis of Rafts with Piles). This
program is used to analyse a tall building that was
constructed on a piled raft foundation, and a
comparison is made of the calculated and observed
behaviour. Chen J etal [4] has presented a nonlinear
analysis method for simulating the interaction of
superstructure –pile-raft-soil system in layered
soil.The flexibility coefficients of the pile-pile and
the pile-soil are deduced , the stiffness matrix of
the pile-soil system is established, and interaction
equation of superstructure –pile-raft –soil system is
formulated. The distribution of the settlement of
the foundation ,which was large in the middle and
small in the boundary and like a dish, was
consistent with the measured data in field.
Further using nonlinear analysis method and
program of the interaction of superstructure-pileraft-soil system in layered soil ,reaction force on
pile head and displacement characteristic of raft
of the piled raft foundation were analysed when
the thickness of the raft, spacing of piles ,length and
diameter of piles were changed. Recently it has
been found that piled-rafts having non-identical
piles shows efficient performance, researchers
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[36,5,35,6] had worked in the field of piled-raft
with non-identical pile lengths.Tan Y.C etal [36]
has given a design approach in which foundation
of medium rise building is designed using skinfriction piles of different length with longer piles at
the center and progressive shorter pile towards the
edge.For detailed design of foundation two cases
were considered.Case 1 considers
overall
settlement behavior of foundation system to predict
settlement profile for structural design .Meanwhile
case 2 considers interaction between the pile-soilstructure (foundation raft) of foundation system to
determine load distribution and local settlement of
piles and also structuraldesign of
raft to
complement case 1. The foundation system was
monitored and the results obtained showed that
foundation system adopted performed satisfactory.
Chow H.S.W etal [ 5] have used finite layer method
for the analysis of piled rafts with piles of different
lengths and diameters. The soil is divided into
horizontal layers with different material properties
and only vertical loads may be applied to the raft.
Interactions between raft-soil-pile are computed
Comparisons of actual measurements and the
results of finite element calculations have shown
that the finite layer method can provide reasonably
accurate solutions. It is very easy to prepare data
for the finite layer analysis as only the pile
locations and properties need to be specified, and
the piles discretised into linear elements. This
method is more efficient than the conventional
three-dimensional finite element analysis. Tan Y.C
etal [35] discussed methodology of a floating
piled raft foundation system consisting of nonidentical piles with longer piles in central portion
and progressively shorter piles towards edge for
medium rise building (5-storey) on soft clay.Two
major cases were considered for detail foundation
analysis and design. Case 1 of pile-soil-structure
interaction was taken in consideration to determine
stress distribution, deformation and settlement of
raft and piles. Case 2 considers overall settlement
behavior of piled raft (immediate and consolidation
settlement). Chow H.S.W [6] has done her Phd
thesis on behavior of piled rafts supported by
non-identical piles examined by use of computer
program APRILS based on finite layer and finite
element methods.The finite layer method is used
for analysis of layered soil system. This method can
be applied different shape of loadings and has
shown good agreement with the theoretical
solutions.The FEM is used for analysis of raft and
piles. Full interaction between raft, piles and soil is
considered in the analysis.
2.2 Study of pile raft system on sand and
weathered rock:This section of the paper deals
with piled –raft foundation system in sandy soil and
weathered rock conditions. The researchers [2, 18,
and 34] have studied effect of piles and raft in a
piled-raft foundation system founded in sand
separately and find out the behavior of piled-raft
foundation as whole. Cao X.D etal [2 ] have carried
out study on behavior of model rafts resting on
disconnected piles which act as reinforcement in
base soil (sand in this case ) rather than structural
element . By varying factors such as raft stiffness,
pile length, pile arrangement, and pile number,
results of the investigation indicate that structurally
disconnected piles are effective in reducing the
settlement and bending moment in model rafts.
Nemoto H.etal[18] have carried out series of
experimental and analytical
study
on the
behaviors of model pile groups and model piled
rafts in dry sand subjected to static vertical load
and static cyclic horizontal load to establish an
adequate analytical method and seismic design
method . An emphasis was placed on the
influence of the connection condition between
the pile head and raft on the behaviors of the
model foundations .The test apparatus including
model foundations , model ground , loading ,
measuring devices and test procedure were
described in detail. Sonoda R.etal [34] has applied
simple conservative design approach for design of
foundation. As per design approach building and its
foundation were constructed in sandy ground using
a reverse construction method. The main difference
between a reverse construction method and a
conventional construction method is that the piles
are cast in place and are partially loaded by the
superstructure early during the construction
process. It is only later that the raft (mat
foundation) is constructed to combine with the piles
to bear the full building load. To examine the
validity of the design method, settlements of the
foundation were observed during construction. The
measured settlements were smaller than those
predicted in the design stage, satisfying the design
requirements for the building design.
In recent years analysis of piled-raft foundation in
sandy subsoils using finite element code has
increased exponentially. The researchers [23,22, 20,
21, 1, 11, 42 and 9] had carried out extensive
research in the same. They have used various finite
element codes to incorporate the exact field
conditions.Paranmoyes etal [ 23] have illustrated
the process of design of a piled raft foundation for a
large residential development using a three stage
procedure, consisting of an initial assessment of the
feasibility of the design, a middle stage of refining
pile locations and depths, and a detailed design
stage of assessing the behaviour of the foundation
under various loading cases using GARP8
computer program. The utilization of a piled raft
foundation versus a conventional piled only
foundation delivered the required serviceability
performance with regard to total and differential
settlements while providing cost savings estimated
to be of the order of 30% versus the original pileonly solution Oh E .Y. N.etal[20] have carried out
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parametric study on piled raft foundation in sand
using numerical modeling with three typical load
intensities of serviceability load. The maximum
settlement of the piled rafts depends on the pile
spacing and the number of piles; while the raft
thickness does not have a significant effect. The
increase in raft thickness reduces the differential
settlement in the foundations. The raft-soil
stiffness
(Krs) is shown to influence the
differential settlement and has the largest influence.
Oh E .Y. N.etal[21] have studied analysis of unpiled and piled raft foundations with sandy soil
conditions similar to those found in Surfers
Paradise of Australia. For the unpiled raft, the
normalized settlement parameter (IR) for the raft
sizes of 8m×8m and 15m×15m ranged as 1.02-1.15,
and 0.64-0.81 respectively. In the case of the piled
raft with raft thicknesses of 0.25, 0.4,0.8, 1.5 and
3m, the corresponding maximum settlements are
64, 63.3, 62.6, 62.3 and 62.2 mm, and the bending
moment values are 107, 160, 321, 446 and 485
kNm. The piles are 0.7m diameter and 16m length.
Three values of intensity of loading as 215, 430 and
645kN/m2 were studied. Figure 4 illustrates the
symmetric idealization of the piled raft problem.
Baziar M.H etal [1] have investigated bearing settlement behavior of combined pile-raft
foundations on medium dense sand Numerical
simulation was also carried out on the model test,
using FLAC-3D, to show compatibility of the
numerical analysis with the test.Fig 5. Shows
numerical model mesh for piled raft and its
surround soil in simulation of 1g physical test.
`
Figure 4: Finite element dealization of pile raft
system
Obtained results showed very good accuracy of the
numerical method used in this study as long as the
applied load does not exceed the working load,
while the performance of numerical model was
relatively good for the loads beyond working load.
Justo J.L etal [11 ] have studied structure of a
copper concentrate store founded on reinforced
concrete raft supported by 697 piles. The piles are
fitted on a dense sand layer , but there are clay
layers of medium consistency along the shaft
and below the support soil.Owing to this , the
piles are subjected to negative skin friction , the
raft has suffered important settlements , the
structure has been damaged and the upper
conveyor belt has experienced problems.A 3-D
finite element (FE) calculation has permitted
calculation of the displacements and stresses in the
piles, raft and structure. A 3-D finite element (FE)
calculation has permitted calculation of the
displacement and stresses in piles, raft and
structure.
Figure 5: Numerical model of pile-raft Foundation
under 1g physical test using FLAC-3D a) Total
mesh b) pile raft mesh
Ziaie-Moayed R.etal[42] have evaluated piled raft
foundations behavior with different dimensions of
piles.element program. They found that piled raft
foundation with different pile diameters may be a
good solution to reduce total and differential
settlements if the bottom layer is dense soil but if
bottom layer is soft soil then in that case piled raft
system with different pile lengths can control
differential and total settlements. Giretti.D [ 9] has
done
Phd work in Modelling of Piled raft
foundations in sand. The main aim of thesis was to
highlight the effects of the raft–soil–pile
interactions on the resistance sand. Researchers
[38,39 and 7] have carried out work on case studies
comparing the values of design settlement with the
measured values after
execution of the
projects.Yamashita K etal [38] have studied a case
history of design and performance of piled raft
supporting a 162 m high residential tower.Field
measurements were performed on settlement and
load sharing of a piled raft supporting a 162m
high isolated residential tower from beginning of
construction to eight month after the end of
construction.At eight months after the end of
construction, the measured settlement was 24mm
and the ratios of the load carried by the piles to
the effective load were estimated to be 0.88-0.94,
which were consistent with the design values of
the foundation settlement and load sharing
between raft and piles. Yamashita.K etal [39] have
studied a case history of seven-storey building of
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piled raft on loose sand underlain by soft silt
layers .In order to reduce consolidation settlement
of the soft silt and to cope with liquefiable loose
sand, a piled raft combined with gird –form
ground improvement was adopted. The design of
the foundation was found appropriate by field
measurements which concerned settlement ,axial
forces of the piles and earth pressures and pore –
water pressure beneath the raft from the
beginning of construction to time about four
years
after
the end
of construction. ElMossoallamy Y. etal [7] have done general over
view on recent innovative applications (case
studies) of piled rafts in Germany on Frankfurt
clay, Berlin sand and Marl and weathered rock for
highway bridges .The piled raft foundation provides
a new geotechnical concept not only for high rise
buildings but also for residential buildings and
bridges, which allow a high grade technical and
economical optimization of construction. Any kind
of eccentric construction can be safely founded on
soft to stiff clay and also on loose to medium
dense sand by appropriate location of piles
,staggering the pile length and suitable pile
diameter .The number and length of piles, the pile
load share ,total bearing capacity of piled raft and
its settlement are main criteria that should be
investigated during a feasibility study to check
the validity of piled raft. Sometimes geological
conditions at site consist of weathered rocks on
which piled raft foundation has to be laid. Recently
high rise buildings are founded on weathered rock
especially in Middle east countries. This has lead to
development of interest of group of researchers [3,
7, 26, and 10] in field of piled- raft foundation on
weathered rocks. Chaudhary M.TA [ 3 ] have
investigated application of a group of 1072 piles for
controlling settlement of an important and sensitive
structure founded on weak rock.2D axisymmetrical and 3D finite element models were
employed to model the 9.0 m thick and 76 m
diameter circular raft, underlying soil/rock and a
mix of annular and orthogonal pile layout.
Effectiveness of pile foundation in reducing
settlement was assessed by comparing the results
with the case of raft foundation alone. Poulos H.G
etal [26] have outlined the processes followed in
the design of the foundations for the Burj Dubai
and the independent verification of the design. The
maximum settlement predicted by ABAQUS for
the tower and podium foundation compares
reasonably well with the maximum settlement
estimated by the revised PIGS analysis carried out
during the independent verification process.
Ibrahim K.etal [10] have carried out piled raft
foundation design analysis of Pentominium tower
in Dubai,UAE in local carbonate soils and rock.
Geotechnical investigations were outlined along
with effect of proposed tower on neighboring
structures, single-pile
response and impact of
cyclic degradation were assessed. Numerical
analyses was used to evaluate the overall piled
raft response under various static and wind
loading combination as well as some techniques
were used to optimize the foundation design,
including preliminary pile testing.
3. CONCLUSIONS
Following conclusions can be drawn from the
various research studies:

Piled-raft foundation can be successively
applied in weak sub-soil conditions i.e. clayey,
sandy and weathered rock .Piled –raft foundation
proves to be cost effective compared to other type
of foundation systems

Finite element method is most efficient
method to analyze complex nature of piled-raft
foundation behavior in clay, sand and weathered
rock. The composite piled-raft, piled-raft with nonidentical piles, etc are the latest modification in
conventional piled-raft system and found to be
efficient with respect to geological and loading
4. REFERENCES
[1]
M.H Baziar, A Ghorbani, R Katzenbach.
Small-Scale Model Test and Three-Dimensional
Analysis of Pile-Raft Foundation on MediumDense Sand. International Journal of Civil
Engineering. Vol. 7, No. 3, pp 170-175, 2009.
[2]
X D Cao, H. Wang and M F Chang
.Behavior of Model Rafts Resting on PileReinforced Sand, Journal of Geotechnical and
Geoenvironmental Engineering Vol. 130, No. 2, pp.
129-138, 2004.
[3]
M .TA Chaudhary. FEM modeling of a
large piled raft for settlement control in weak rock
Engineering Structures 29, 2901–2907, 2007.
[4]
J Chen, Y Chang and Y Zou. Key
engineering
Materials
(Volumes
400
402):Advances in Concrete and Structures, pp. 651658
[5]
H.S.W Chow and J.C Small. Behavior of
Piled Rafts with Piles of Different Lengths and
Diameters under Vertical Loading. Advances in
Deep Foundations (GSP 132), 2005.
[6]
H.S.W Chow. Analysis of piled-raft
foundation with piles of different length and
diameter ,Phd
Thesis, 2007.
[7]
Y.El-Mossoallamy, B.Lutz and T.Richter.
Innovative application of piled raft foundation to
optimize the design of high-rise buildings and
bridge foundations,10th International Conference
on piling and deep foundations, Amsterdam 2006.
[8]
F.Garcia,A.Lizcano,
and
O.Reul
Viscohypoplastic Model Applied to the Case
History of Piled Raft Foundation. Geotechnical
Engineering in the information Technology Age,
Atlanta,GA 1-6,(2006).
[9]
D. Giretti .Modelling of piled raft
foundations in sand ,Phd thesis (2009)
[10]
K
.Ibrahim,
G
Bunce
and
C.Murrels.Foundation design for the Pentominium
ISSN: 0975 – 6744| NOV 10 TO OCT 11 | Volume 1, Issue 2
Page 44
JOURNAL OF INFORMATION, KNOWLEDGE AND RESEARCH IN
CIVIL ENGINEERING
tower in Dubai,UAE,Proceedings of ICE , Civil
Engineering 162, pp 25–33, 2009.
[11]
J.L Justo, A .Jaramillo, M .Vazquez, E
.Justo and M.T. Perez .The performance of piled
raft foundations, Proceedings
of the
17th
international conference on Soil Mechanics and
Geotechnical Engineering (ICSMGE 2009): 12281231.
[12]
J Lee, Y .Kim, J .Sangseom Threedimensional
analysis of bearing behavior of
piled raft
on soft
clay. Computers and
GeotechnicsVolume 37 Issue 1-2, pp. 103-114
,2010,
[13]
F.Y.
Liang, L.Z. Chen, X.G.
Shi.
Numerical analysis of composite piled raft with
cushion subjected to vertical load. Computers and
Geotechnics 30 (2003) 443–453
[14]
F. Liang, J Li and L. Chen .Optimization
of Composite Piled Raft Foundation with Varied
Rigidity of Cushion. Proceedings of Sessions of
GeoShanghai 2006 .Foundation Analysis and
Design –Innovative methods (GSP 153) 29-34.
[15]
S.S Liew, S.S Gue and Y.C Tan Gue &
Partners
Sdn
Bhd,
Kuala
Lumpur,
Malaysia.“Design and Instrumentation Results of A
Reinforcement Concrete Piled Raft Supporting
2500 Ton Oil Storage Tank On Very Soft Alluvium
Deposits”, Ninth International Conference on Piling
and Deep Foundations, Nice, 3rd – 5th June, 2002.
[16]
D.K Maharaj and S.R Gandhi .Non-linear
Finite
element
analysis
of
piledraft
foundations.Proceedings of the Institution of Civil
Engineers Geotechnical Engineering 157, 2004
Issue GE3 Pages 107–113.
[17]
D.K.
Maharaj.
Three
DimensionalNonlinear Finite Element Analysis to
Study the Effect of Raft and Pile Stiffness on the
Load-Settlement Behaviour of Piled Raft
Foundations.Electronic Journal of Geotechnical
Engineering ,Volume 9 , Bundle A ,(2004).
[18]
H. Nemoto Yaegashi K, Takeuchi
Y,Nishimura N,Matsmoto T and Kitiyodom P.
vertical load tests of model piled rafts withdifferent
pile head connection conditions,Proceedings of the
Sixth International Conference on Physical
Modelling in : Geotechniques, Hongkong 2006 pp
853-859 .
[19]
J Novak, L.C. Reese, and S.T.Wang.
Analysis of Pile-Raft Foundations with 3D FiniteElement Method. Proceedings of the 2005
Structures congress and 2005 Forensic Engineering
Symposium,New York.
[20]
E.Y.N Oh , Q.M Bui , C. Surarak, R
.Adamec and A.S. Balasurbamaniam Parametric
Study on Piled Raft Foundation in Sand Using
Numerical Modeling ,www.griffith.edu.au
[21]
E.Y. N Oh, M. Huang, C Surarak, R.
Adamec and A.S. Balsurbamaniam. Finite element
modeling for piled raft foundation in sand. Eleventh
East Asia-Pacific Conference on Structural
Engineering
&Construction
(EASEC-11).
“Building a Sustainable Environment” November
19-21, 2008, Taipei, Taiwan.
[22]
E.Y.N Oh, D.G Lin., Q.M Bui. , M.
Huang, C.Surarak andA.S. Balasubramaniam
Numerical analysis of piled raft foundation in
sandy and clayey soils.Proceedings of the 17th
International conference on Soil Mechanics and
Geotechnical Engineering (ICSMGE 2009): 11591162
[23]
Paranmoyes , H.G. Poulos , J.C. Small
and F. Badelow . Piled raft design process for a
high-rise building on the gold coast, Australia.
TALL BUILDINGS from Engineering
to
Sustainability: 6th International Conference on Tall
Buildings, Mini Symposium on Sustainable Cities,
Mini Symposium on Planning, Designand SocioEconomic Aspects of Tall Residential Living
Environment,Hongkong , pp241-249.China 2005.
[24]
H. G Poulos,. Piled raft foundations:
design and applications, Geotechnique 51(2001),
No. 2, 95- 113
[25]
H.G Poulos Simplified design procedure
for piled raft foundation .Deep Foundation
2002:441-458.
[26]
H.G Poulos and G.Bunce. Foundation
design for the burj dubai – the world’s tallest
building. Proceedings of the 6th International
conference on Case Histories in Geotechnical
engineering, Arlington, VA, 2008
[27]
M. Rabiebi.Parametric Study for Piled
Raft
Foundations ,Electronic journal of
Geotechnical Engineering Volume 14 ,Bundle A
,2009.
[28]
M. Rabiebi .Effect of Pile Configuration
and Load Type on Piled Raft. Proceedings of
Sessions of Geoshanghai 2010 : Deep Foundations
and Geotechnical Insitu testing
Geotechnical
special publication no. 205:34- 41
[29]
O. Reul .Numerical Study of the Bearing
Behavior of Piled Rafts . International Journal of
Geomechanics, Vol. 4, No. 2, 2004, pp. 59- 68
[30]
O. Reul and M.F Randolf . Piled rafts in
overconsolidated clay: comparison of in situ
measurements
and
numerical
analyses,
Geotechnique 53, No. 3, 301–315, (2003).
[31]
L.D Sanctis and Alessandro, A Mandolini
Bearing Capacity of Piles Rafts on Soft Clay soils.
Journal
of
Geotechnical
and
GeoenvironmentalEngineering, Vol. 132, No.12,
2006, pp. 1600-1610,
[32]
Y.K
Seo, K.S Choi and S.G Jeong
Proceedings of the 13th International Offshore and
Polar Engineering Conference: Design Charts of
Piled Raft Foundations on Soft Clay: Honolulu,
Hawaii, USA, May 25–30,2003
[33]
JC Small and HG Poulos.Non-linear
Analysis of Piled Raft Foundations. Proceedings of
Sessions of Geo-Denver: Contemporary Issues In
Deep Foundations (GSP 158) 2007.pp 1-9
ISSN: 0975 – 6744| NOV 10 TO OCT 11 | Volume 1, Issue 2
Page 45
JOURNAL OF INFORMATION, KNOWLEDGE AND RESEARCH IN
CIVIL ENGINEERING
[34]
R Sonoda, T Matsumoto, P Kitiyodom, H
Moritaka, and T Ono. Case study of a piled raft
foundation constructed using a reverse construction
method
and
its
post-analysis,
Canadian
Geotechnical Journal. 46(2): 142–159 (2009).
[35]
YC Tan, SW.Cheah and M R Taha
Methodology for Design of Piled Raft for 5Storey Buildings on Very Soft Clay. Proceedings of
Sessions of GeoShanghai 2006 Foundation
Analysis and Design – Innovative Application
(GSP153) 226-233
[36]
Y.C Tan, C.M Chow and C.M Gue
Gue & Partners Sdn Bhd, Kuala Lumpur, Malaysia
.Piled medium-rise buildings on very soft clay
2004.
[37]
L.G Vásquez, S.T Wang, and W.M
Isenhower Estimation of the Capacity of Pile-Raft
Foundations by Three- Dimensional Non-Linear
finite Element Analysis Geo Congress 2006:
Geotechnical Engineering in the information
Technology Age (2006) 1-6 .
[38]
K.Yamashita,J.Hamada
and
Y.Soga.
Settlement and Load Sharing of Piled Raft of a 162
m High Residential Tower. Proceedings of Sessions
of
Geoshanghai
Deep
Foundations
and
Geotechnical Insitu testing. Geotechnical special
publication no. 205:26-33
[39]
K.Yamashita and T. Yamada Settlement
and load sharing of a piled raft with ground
improvement on soft ground, Proceedings of the
17th International Conference on Soil Mechanics
and Geotechnical Engineering 2009: 1236-1239
[40]
M.H Zhao, L. Zhang, M.H Yang.
Settlement calculation for long-short composite
piled raft foundation. Journal of Central South
University of Technology, Volume 13 No.6 749754,(2006).
[41]
J.J Zheng, S.W Abusharar,and X.Z Wang.
Three- dimensional nonlinear finite element
modeling of composite foundation formed by
CFG–lime piles. Computers and Geotechnics 35
(2008) 637–643
[42]
R. Ziaie-Moayed, M. Kamalzare and
M.Safavian .Evaluation of piled raft foundations
behavior with different dimensions of piles. Journal
of applied sciences 10(13):1320-1325,2010
ISSN: 0975 – 6744| NOV 10 TO OCT 11 | Volume 1, Issue 2
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