碎石桩加固可液化场地工程地震响应分析

Seismic response analysis for stone column improved liquefiable ground

以北京顺义区潮白河西岸某工程项目为背景,利用砂土液化大变形本构模型在FLAC3D平台中进行流固耦合动力反应分析,对工程采用碎石桩作为抗液化措施的效果进行评价,研究了可液化场地碎石桩加固复合地基、基础及上部结构系统的地震动力响应、抗液化加固效果以及震后沉降变化规律。该工程场地所处的河滩区域由潮白河改道演变而成,砂土与粉土存在地震液化可能性,加固处理设计方案为振冲碎石桩,主要目的是完全消除地基砂土液化和提高加固后桩间土的地基承载力。所采用的计算分析方法能够考虑土体与孔隙水动力流固耦合过程,本构模型能够考虑循环荷载作用下饱和砂土超静孔隙水压力的累积和土体液化变形。分析结果表明,在未加固区出现液化的情况下,经碎石桩加固场地的抗液化效果得到显著改善,碎石桩加固显著提高了复合地基整体的超静孔压消散速度,大幅降低了可液化场地的震动沉降。

This paper is based on a building project on the west bank of Chaobai River in Shunyi,Beijing.The large deformation constitutive model of sand liquefaction was used to analyze the fluid-structure coupled dynamic response on FLAC 3 D platform.The effect of stone column as anti-liquefaction measure is evaluated.The seismic dynamic response,anti-liquefaction reinforcement effect and post earthquake settlement of composite foundation,foundation and superstructure system strengthened by stone column in liquefiable site were studied.The site was formed due to the Chaobai River diversion.The sand and silt soils at the site exhibits liquefaction potential.The vibro-replacement stone column method was used to mitigate liquefaction and improve ground bearing capacity.The analysis method took the dynamic solid-fluid coupled process into consideration,and adopted a constitutive model that incorporated the generation of excess pore pressure in saturated soil and relevant deformation under cyclic loading.The results indicate that while the non-improved areas suffered intensive liquefaction,stone column improved ground showed significant effects in liquefaction mitigation.The stone column improvement increased the excess pore pressure dissipation rate within the compound foundation,and reduced the seismic induced settlement of the improved ground.