倾斜液化场地桩基地震响应离心机试验研究

 倾斜液化场地中群桩地震响应受液化土层侧向流动和桩土相互作用影响和控制，故倾斜液化场地中桩基抗震性能问题是一个极其复杂问题。基于动态土工离心机试验来探讨考虑倾斜液化土侧向流动特点的群桩地震响应规律。试验设计不同地震强度下2个50 g典型土工离心模型试验，以研究倾斜液化场地中桩土加速度、位移、桩身弯矩和土体超孔隙水压力响应特性。试验提出倾斜饱和土层的制备方法，再现倾斜液化场地中桩基础在强震作用下的破坏程度、状态和机制，并进一步对比分析试验结果，取得较好的成果，此为倾斜液化场地桩基础的抗震设计提供可靠依据，对确保液化场地桩基础的抗震稳定性和安全性具有重要意义。

DYNAMIC CENTRIFUGE TESTS OF SEISMIC RESPONSES OF PILE FOUNDATIONS IN INCLINED LIQUEFIABLE SOILS

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.