dc.description.abstract |
Due to the complex nature of the piled raft foundation, its realistic design relies on the
more rigorous computer based methods using either finite element or finite difference
based soft wares. This study develops a numerical method that incorporates the different
interactions which are the main causes of the complexity of piled raft foundation using
a finite difference based software F LAC3D. Both unpiled raft and piled raft foundations
were modeled using F LAC3D. The dimension of raft, pile spacing ,diametere and length
of piles, stiffness of underlain soil were used as parameters. The study includes the study
of piled rafts subjected to lateral loads. The raft thickness is set so that the raft flexibility
is to be in the range of 0.1 to 5 in order to make the raft experiences both bending
moment and settlements. The study presents the load settlement relationship and the
bending moment result of the raft and the piles, which were run in large strain analysis.
For the purpose of checking weather the model developed was in appropriate accuracy,
two validating materials were used for the vertical loading case. One is an experimentally
studied research (used as a verification material) and the second is a study conducted using
different methods of piled raft analysis. The result of both validation materials show
that the model is in good accuracy. Moreover, a centrifuge model was used to validate
the piled raft subjected to lateral load. The interfaces between the soil and the structural
elements(the raft and piles) were appropriately modeled by providing the interface
deformation and strength properties. The deformation properties refers the normal and
shear directed stiffness and the strength properties are the cohesion and angle of friction.
The structural elements (piles and rafts) are assumed to act in the linear elastic range
and hence, elastic isotropic constitutive model is used. However, Mohr-Coulomb elasticperfectly
plastic model is used for soil materials. The p-multipliers of piled rafts for pile
spacing of 3D and 5D were computed. The pile spacing were in both directions and it
has been observed that the pile spacing in the direction transvese to the loading direction
has not effect on the pile pile interactions in the case of lateral load. Application of vertical
load to piled rafts subjected to lateral load decreases the lateral displacement of piles. |
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