2654
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
ratio defined as a ratio between the column length and the
mobilized length for skin frictions.
Jeong and Cho studied the settlement behavior of piled raft
foundations by 3D numerical analysis on case studies. Attention
is given to the improved analytical method (YSPR) and
interactive analysis considering raft flexibility and soil
nonlinearity. It was found that the proposed method in present
study is in good agreement with general trend of the field
measurements. Conclusions are:. Proposed analytical method
produces a considerably larger settlement than the results
obtained by the conventional methods (GSRaft). The proposed
method is shown to be capable of predicting the behavior of a
large piled raft. Nonlinear load-transfer curve and flat-shell
element can be used to improve the existing numerical methods.
Jung et al. introduced a new development of multiplexed
Fiber-optic Bragg Grating (FBG) sensors to measure lateral pile
displacements. With the pile displacement calculated under
lateral load, the data were compared with the measured ones.
Three optimization strategies—positioning sensors at regular
intervals, positioning sensors at projected Gaussian points but
not following the Gaussian rule, and positioning sensors exactly
based on the Gaussian rule—were implemented. In both cases
for the 1st and 2nd strategies, the measurement error decreases
as the number of sensors increases. Moreover, positioning the
sensors rigorously based on the Gaussian quadrature rule
enhances the accuracy more than just using the Gaussian points.
Kaneda et al. presented the numerical simulation of field
tests on bearing capacity of pile, raft, and piled raft foundations.
The SYS Cam-clay model developed at Nagoya University was
used. Material parameters were determined by laboratory tests
considering the state of stress in the field. Agreeable results
were found between predictions and field tests. Furthermore, it
is found that the total bearing capacity of the raft and the piles is
equal to that of the piled raft foundation. This was also
confirmed via the simulations. The authors explained the reason
of such phenomenon.
Kang et al. introduced the Fiber Reinforced Plastic (FRP)
pile and applications. To improve axial and lateral load
capacities, a Hybrid Concrete Filled FRP Pile (HCFFP) is
suggested. The load-strain relation of CFFP was compared with
finite element solutions. The confinement effect between FRP
Pile and CFFP are shown. Load capacity of HCFFP member is
increased if confining pressure and concrete strength are
increased. In addition, the equations to predict the compressive
and flexure strengths of the HCFFP member are proposed. It
was confirmed that HCFFP is suitable to apply as the structural
elements with the comparisons of CFFP member. It’s suggested
that the structural performance of connection between the
segments of HCFFP, and constructability of HCFFP pile should
be explored in the future for more practical applications.
Korff and Mair investigated the ground displacements
related to deep excavations on a case study of North South
Metro Line in Amsterdam. It was found that the response of
buildings is governed by soil displacements resulting from the
excavation. It is concluded that the surface displacement behind
the wall is 0.3~1.0% of the excavation depth, if all construction
works are included. The largest effect on the ground surface
displacement (55~75%) can be attributed to the diaphragm wall
construction, jet grout strut installation and construction of the
roof and took in total about 4 years. The actual excavation stage
caused only about 25-45% of the surface displacements. At
larger excavation depths the influence zone is found
significantly smaller than 2 times the excavation depth.
Lehtonen introduced the use of steel piles in retaining wall
construction and energy transfer. Open section drilling for new
micropile inventions is discussed. Drilled pile walls and energy
transfer applications extend the use of drilled piles to sites
where conventional piling is rarely seen as an option and where
the drilled piles can be installed as hybrid structures,
functioning as vertically loaded piles, or retaining structure, or a
heating/cooling energy reservation system.
Levy and Richards confirmed that base suction may
contribute significantly to footing performance. Field tests on
full scale footings were carried. The suction developed is
similar to physical model tests using centrifuge. The design
uplift performance is not reached before the ultimate limit state
displacement criterion set by UK design guidance. In the case
where suctions did not develop, the uplift performance of the
footings was extremely poor. Such a poor performance will
require a re-evaluation of the use coarse granular material, when
used in excavations bounded by London clay.
Look and Lacey implemented two land based test piles
fitted with Osterberg cells for testing the shaft capacity of the
sedimentary bedrock at the Gateway Bridge site. Based on the
test data, the required magnitude of the input unconfined
characteristic strength (UCS) of the rock were back calculated
for various pile design methods. It was concluded by the authors
that five of the examined methods produced results which
matched the observed shaft capacities by adopting a design
UCS value close to the UCS lower quartile “characteristic”
value.
Lorenzo et al. described how to find out bearing capacity of
piled raft foundation at ultimate stage which governs the design
of PRs with a raft width between 6 to 14m using limit state
approach. Author proposed the relation to find out ultimate
bearing capacity of PR with the help of numerical model. To
apply limit state method, floating piles behaviour is considered
under ultimate or limiting capacity and design equation were
presented. Global factor of safety considered in the design.
Partial safety coefficient of resistant load was found out. Taylor
series method was adopted to find bearing capacity of PR. This
analysis is generalized method for the calculation for
determining the bearing capacities of raft and pile groups
separately.
Mayne and Woeller suggested a closed-form elastic
continuum solution for upper and lower segment responses of
bored piles subjected to bi-directional Osterberg load testing.
Seismic piezocone tests (SCPTu) are used to provide data for
assessing the capacity, while the shear wave velocity provides
the fundamental stiffness for displacement analyses. A load test
case study involving two levels of embedded O-cells for a large
bridge in Charleston, South Carolina is presented to illustrate
the approach. Results from the seismic piezocone testing
provide the necessary input data to evaluate axial side and base
resistances of the deep foundations, as well as the small-strain
stiffness (G
max
) needed for deformation analyses.
Mendoza et al. discussed the observations learned from
Metro-Line 12 overpass in Mexico City soft clay. A pioneer
foundation of footing or foundation slab with long skirts was
used first time in the city. Geotechnical sensors and
accelerometers were installed to monitor during the construction
and long term operations as well as strong earthquakes A first
earthquake of low intensity caused a sudden, reduced and
transitory horizontal pressure decrease on the walls, but a rapid
recovery of the sustained loads was observed. The Metro trains
impose no significant changes in vertical pressure under the
footing, nor on lateral pressures or pore water pressures on the
sides of the perimeter walls.
Miller et al. discussed the applications of shaft grouting to
improve pile foundation capacity in Georgia. Poor ground
conditions and high loads were encountered and the deep bored
piles were installed. Results from the strain gauges showed
differences in the behaviour of the piles in different strata
depending on the granular content of the material. It was found
the shaft grouting improved the skin friction of the strata with a
high sand and gravel content by a factor of 2.2~2.4. Some
improvement was achieved in material with as little sand
content (<10%). It was reported that the shaft grouting
improved the load-displacement behaviour of the test pile with
settlements reduced by approximately 50%.
Perälä presented a new technology called as polymer pillar.
The product is patented and mainly made by injecting
