碎石桩复合地基三维地震响应分析

将饱和砂土视为土—水两相介质,以Biot动力固结方程为基础,编制了完全耦合的三维排水有效应力动力反应分析程序。利用该程序对碎石桩复合地基进行了动力反应分析。结果表明:在地震荷载作用下,碎石桩具有明显的减震效应,碎石桩复合地基表层的最大水平振动加速度与天然地基相比明显减小,并且碎石桩对地基的沉降变形有明显的抑制作用;碎石桩的排水效应十分显著,随着输入地震加速度的减弱,在孔压达到峰值以后,由下到上出现了明显的孔压消散现象,碎石桩排水效应的影响范围为上窄下宽的圆台形;碎石桩的加密效应显著;考虑碎石桩各效应的耦合作用比仅考虑其单一效应,计算得到的孔压比要小,因此在进行碎石桩复合地基抗液化判别时,应该综合考虑碎石桩各效应的相互耦合作用。

BIOT'S CONSOLIDATION THEORY BASED THREE-DIMENSIONAL NUMERICAL ANALYSIS FOR EARTHQUAKE RESPONSE OF STONE COLUMNS COMPOSITE FOUNDATION

Saturated sand was looked as a soil-water two-phase medium. A fully coupled three-dimension effective-stress dynamic analysis software was developed on the basis of Biot's consolidation theory. Stone columns composite foundation was analyzed using software. The research shows that the reduced vibration effectiveness of stone columns is very remarkable, and the surface maximum horizontal vibration acceleration of stone columns composite foundation is bigger than that of natural foundation. Moreover, the stone columns can restrain settlement of foundation. The drainage effectiveness of stone columns is very remarkable. With decreasing of input earthquake acceleration, the dissipation of pore water pressure starts after the peak value has reached. The effective influence domain of stone columns is a circling platform with narrow upside and wide underside. The densification effectiveness of stone columns is remarkable. The excess pore water pressure ratio considering coupling effectiveness is smaller than that only considering some effectiveness or other. So the coupling effectiveness of stone columns should be considered when judging of anti-liquefaction capability of stone columns composite foundation.