2652
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
centrifuge test data. Conclusions are: The load carried by the
piles is higher for a rigid raft (K
f
> 10) due to the minimal
interaction between the raft and subsoil compared to the
perfectly flexible raft (K
f
< 0.01). The spacing between piles
can be used to evaluate the raft flexibility instead of its width
(Eq. 2 in this paper). The load carried by piles increases as pile
diameter increases. However, the rate of increase is higher for
small size piles and diminishes as the pile diameter increases.
Ashlock and Fotouhi performed full-scale pile vibration test
for steel HP piles installed to a depth of 6 m in a soft clay
profile, with one pile being surrounded by a cement-deep-soil-
mixed (CDSM) improved zone. Authors conducted multi-modal
tests with vertical and coupled lateral-rocking vibrations using a
shaker mounted on a rigid pile cap. It was observed that the
improved soil zone significantly increased the stiffness of the
measured vertical response, but had little effect on the lateral-
rocking mode. Results of the forced vibration tests were
analyzed using methods reported in the literature and it was
found that the simplified model was able to capture the vertical
response reasonably well in both the improved and native
unimproved soil profiles along with the lateral response in
unimproved soil.
Balakumar et al. developed a new design method for pile
raft foundation in cohesionless soil for different densities. This
design procedure constitutes two stages; First stage of design
procedure regarding to determination of the optimum number of
piles, pile length and diameter required to be placed in a
strategic manner to produce the required settlement reduction
along with the load shared by the pile group. Second stage of
design procedure was developed a 3D model in ANSYS finite
element analysis based software and performed an extensive
parametric study. Authors were also performed 1g small scale
model test on circular and square shaped pile raft foundation
and concluded that that the equivalent pier theory could be used
in combination with the pressuremeter test results to predict the
load settlement and load sharing behavior of the piled raft
foundation.
Basile described a practical analysis method for determining
the response of piled rafts. Validity of the analysis was
demonstrated through comparison with alternative numerical
solutions and field measurements. The author suggests that the
negligible computational costs make the analysis suitable not
only for the design of piled rafts supporting high rise buildings
(generally based on complex and expensive 3D FEM or FDM
analyses) but also for that of bridges and ordinary buildings.
Basu et al. presented an approach using the variational
principles of mechanics to analyze torsionally loaded piles in
elastic soil. The total potential energy of the pile-soil system is
minimized to obtain the differential equations governing the
pile and soil displacements. The analysis explicitly takes into
account the three-dimensional pile-soil interaction in multi-
layered soil. The authors found that the soil layering does have
an effect on the pile response, particularly for short, stubby piles
with low slenderness ratio.
Berthelot et al. presented the necessary site investigations
for continue flight auger piles in firm sites. The penetration in
the grounds can be made only with a tool of specific attack
extended by an experimental retractable point in the concreting.
It also requires an important couple of rotation and the means of
vertical pushes. These tests were implanted right adapted soils
investigations highlight well the strong resistances and the very
high modulus of this hard soil. They can validate the anchoring
and help the specificities of each project to bring successful
construction at the sites.
Bilfinger et al. adopted new approach to evaluate safety
assessment of pile foundations which uses Bayesian inference
to combine bearing capacity and field controls which may lead
to economic design. Ultimate load prediction method was used
for bearing capacity determination. Field controls methods were
used to ensure pile settlement within limit. Bayesian inference
which is statistical approach which consider local soil condition
as variable and reported it in terms of equation. This approach
provided sound justification to field operational rules that may
lead to economical foundation solution while maintaining the
same safety level as required by code.
Biswas and Manna conducted a comparative study on
vertical vibration tests of full-scale single piles with three-
dimensional FE analysis using Abaqus/CAE. The resonant
frequency and amplitude obtained from 3D FE analysis were
found compatible to field test results. The resonant frequencies
are decreased with the increase of eccentric moments whereas
the changes of resonant amplitudes are opposite. It increases
gradually with the increase of eccentric moments, and stops
below the ground water table.
Bouafia presented a practical method to construct the P-Y
curves for analysis on lateral load-deflection behavior of single
piles using data from pressuremeter test. Full-scale pile tests
were conducted to validate the predictions. With the
correlations between soil reaction modulus/resistance and
pile/soil stiffness ratio via the parameters from PMT test, a step-
by-step method was suggested to define the parameters of P-Y
curves for single pile under in multi-layered soils. Formulations
of the P-Y curves, methodology to construct the P-Y curve and
the analytical features can be found in this paper.
Bretelle compared the French (Fascicule 62) and Australian
(AS2159) approaches on pile design methodology and shows
their difference with an example. French standard provides the
relationship between measured characteristics and design
parameters as well as a unique set of reduction factors on
resistance. Australian standard leaves the choice to the
engineers and defines different reduction factors on resistance
depending on site geotechnical risk. The ways to account for
pile testing is described is this paper with the example showing
optimization opportunity when pile testing is undertaken on site.
Cannon described the high strain and low strain dynamic
pile testing for assessing the foundation of Messa A Rail Bridge
at Western Australia, which have caused a change in foundation
type from bored pile foundation to a driven pile foundation.
Cross – hole sonic logging (CSL) test was performed at the
required site for testing the test pile statically in tension.
However, during construction, serious problem with the
constructability of the bored pile was detected by both high
strain and low strain dynamic testing. Thus the bored pile was
changed to a driven pile, after its integrity was tested using a
Pile Integrity Tester. Hence, the dynamic pile testing confirmed
the pile resistance, providing high level of confidence in the
foundation.
Carvaldho and Albuquerque presented the test results of
uplift behavior of bored piles in unsaturated sandy soil found in
Southern central region of Brazil. Tests were conducted in on
the campus of the University of São Paulo, located in the city of
São Carlos on three bored piles having length of 10m and
diameter of 0.35m, 0.4m and 0.5m respectively to ascertain load
transfer mechanism to subsoil as well as ascertaining the
applicability of the methods for calculating ultimate load that
are available within the technical milieu. The ultimate loads
(Q
ult
) obtained on the three piles were 387kN, 440kN and
478kN respectively. The determination of the ultimate load
using CPT demonstrates good results when the LCPC Method is
adopted.
Christin et al. introduced the timber pile load test
instrumentation with removable extensometer. As the timber
piles become popularly used in France for retrofitting and reuse
of all historical structures and sustainable development, the load
test on such pile receives attentions. The authors present a
research project “Pieux Bois” (2010-2013) to establish a
database necessary for design methods on timber piles. The first
pile loading test campaign was carried out in Rouen on piles
instrumented with removable extensometers. Interesting results
are discussed in this paper.
