The Research On The Lateral Bearing Behavior Of The Pile Foundation In Liquefiable Soil

The study on the lateral bearing capacity of the pile foundation inliquefying sand under seismic loading becomes a research hotspot ingeotechnical engineering in these decades. There are some simplifieddesign methods for predicting the lateral bearing capacity of the pilein liquefied ground under seismic loading, but these methods have notbeen verified by physical data during the real earthquake or the modeltest. So the lateral bearing capacity of the pile in liquefied ground wasinvestigated through the shake table test in this dissertation. Somemain achievements of this dissertation are described as follows: Shaking table model tests on the pile and the liquefied groundinteraction were implemented to study the mechanism of the change ofthe lateral bearing capacity of the pile in liquefiable ground underseismic loading. By changing the frequency of the input loading, theamplitude of the input acceleration and using the sand with differentparticle size distribution, the model pile with different diameter andthe soil box with different sizes, the effect of these factors on thelateral bearing capacity of the pile in liquefied ground was studied.Some basic results on the pile and liquefied sand interaction were got. Pseudo-static analyses of the model pile system were performedbased on the "Beam on Nonlinear Winkler Foundation (BNWF)" model.In the BNWF model, baseline sets of p-y springs were established foreach test for static loading. The analysis was repeated with differentscalar multiples of the baseline p-y springs (scalar multiplier appliedto the p values) until a reasonable match between calculated andmeasured moments of the pile was obtained. So the method is proposedwhich evaluates p-y springs after the sand has liquefied. A method for back-calculating dynamic p-y curve of liquefiedsand is proposed through the measured moments of the pile, themeasured acceleration at the top of the pile and the measuredacceleration of the soil layer. And by comparing the static anddynamic p-y curve, the change of the lateral bearing capacity of thepile after the sand has liquefied is analyzed. The relationship between the strength of liquefied sand and thep-y curves of liquefied sand was explored. And the tests on thestructural residual strength of liquefied sand were proposed, so thestructural residual strength index of liquefied sand was got. Using theindex and the method recommended by API for p-y curves, the p-ycurves of liquefied sand were got. So a method using the structuralresidual strength to develop the p-y curve of the liquefied sand isproposed.