DYNAMIC CENTRIFUGE TESTS OF SEISMIC RESPONSES OF PILE FOUNDATIONS IN INCLINED LIQUEFIABLE SOILS
WANG Mingwu1，TOBITA T2，IAI S2
(1. School of Civil Engineering，Hefei University of Technology，Hefei，Anhui 230009，China； 2. Disaster Prevention Research Institute，Kyoto University，Kyoto 611–0011，Japan)
Abstract：The problem of seismic performances of pile groups found on the inclined liquefiable soils is a nonlinear and complicated problem because the seismic responses of pile groups are influenced by the pile-soil interaction and lateral spread. Two cases of 50 g centrifuge tests are conducted to investigate acceleration，displacement，bending moment and excess pore water pressure responses of pile groups on the inclined liquefiable soils during earthquake. The scenario input motions with peak shaking amplitudes of 3.64 and 9.68 m/s2(at prototype scale) are adopted in centrifuge tests. A rectangular rigid container is used in two cases. The inclined soil profile is comprised of saturated silica sand resting on stiff bedrock. The fluid material is simulated by deaired motolose solution of 50 times of the viscosity of water such that the deposit has the prototype permeability of sand. The model of pile foundations consists of structure supported by a 2 row×2 row piles，10 times in diameter spacing pile group. Moreover，the results from centrifuge cases are compared. The failure mechanism of pile groups in laterally spreading soils during earthquake is also discussed；and a good result is achieved. It is found that the lateral displacement and bending moments of pile groups are much larger in laterally spreading soils than those in non-liquefiable soils. The location for the maximum bending moment during shaking and residual bending moment transfer further down with the liquefaction and lateral spread of soils. The proposed dynamic centrifuge test is applicable and reliable for simulating seismic performance of pile groups on the inclined liquefiable foundation. These results for insuring the aseismic stability and aseismic safety of pile group in the inclined liquefied soils are potentially very significant.
