Numerical Simulation Of Anti-seismic Characteristics Of The Low Cap Pile Foundation In The Liquefiable Soils

The pile foundation is one kind of deep foundation forms which applied broadest, and suitable almost all situation grounds. Study on lateral, the capacity of pile in the soft soil layers has generally became important subject in the aseismic design of Foundation Engineering throughout the world, however, it disasters occur frequent, especially in liquefiable soil layers through all previous earthquakes. Due to some simplified design theory and zonal experience for predicting the bearing capacity of pile under the seismic loading, obvious deficiencies can be found easily in aseismic design method of pile foundation in liquefiable site used at present. Analytical method and indoor experimental for soft soil improved by gravel pile, are two types of settlement computation methods that used widely, however most Research workers often choose one, nevertheless, many valuable material that hard to meet the need of engineering practice has been collected.Based on the review of past research work from domestic or foreign and the system’s summary to predecessor’s results, many useful material got collected before we starting the research which supported by Province Natural Science Foundation of Shanxi in China " The experiment study of joint actiom of pile and soil under the seismic load ".In the paper, indoors experiment about the low cap pile foundation in the liquefiable soils under earthquake action is stimulated completing by the Three-Dimensional Finite Elements Method Program "midas-GTS"(Geotechnical and Tunnel System) through these macroscopic mechanics parameter that obtains from the experiment’s data. Under the same earthquake wave action, to investigate the seismic responses of the bearing capacity of pile foundation with different pile spacing, and with thickness changing of the cap when considering the resistance of the soil liquefaction capacity. Moreover, to compare the working characteristic of piles in different positions during the earthquake. And the results are reached as shown in the following:1) Under the earthquake load, the The smaller the pile spacing, the stronger ability of liquefaction of the pile foundation, at the same time, the pile foundation also slowed down the speed of pore-water pressure dissipation in original location;2) When the number of the piles to be invariable with different pile spacing, the mainly factor to enhances the capacity of the pile foundation is size of cap rather than the pile spacing under the static load;3) Although the smaller pile spacing provided the more sufficient space to improve the aseismic ability of pile foundation, it is the fact that the capacity is losing gradually follow shaking load continuing during the earthquake, just the smaller losing slowly;4) In the pile foundation with low cap, the plate to be thicker, it’s earthquake resistance performance is more obvious during the earthquake than the same one under the static load. The thicker of the piles’cop, the stronger stiffness to improve the capacity of the resistance liquefaction;5) According to the different position in the pile foundation with low cap, the piles could be divided into three kinds:central pile, pile in the most distant place and pile in edge. They show different feature that the aseismic ability of the central pile is strongest than other two, and the pile in edge is next,through the careful contrast of those curves of the Acp got from the numeric model;6) In the process, the earthquake response of the piles in the edge are different, the aseismic ability of those to meet the seism’s wave came is stronger than others’.