饱和砂土液化刚度变化规律预测与离心模型试验观测  

Stiffness evolution of saturated sand during liquefaction process in centrifugal model test

作　　者：周燕国[1] 周致亮 摄宇 ZHOU Yanguo;ZHOU Zhiliang;SHE Yu(MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering,Institute of Geotechnical Engineering,Center for Hypergravity Experiment and Interdisciplinary Research,Zhejiang University,Hangzhou 310058,Zhejiang,China;Power China Zhongnan Engineering Corporation Limited,Changsha 410014,Hunan,China)

机构地区：[1]浙江大学软弱土与环境土工教育部重点实验室,浙江大学岩土工程研究所,浙江大学超重力研究中心,浙江杭州310058 [2]中国电建集团中南勘测设计研究院有限公司,湖南长沙410014

出　　处：《地基处理》2024年第6期540-546,共7页Journal of Ground Improvement

基　　金：国家自然科学基金项目(51988101,52278374);高等学校学科创新引智计划(B18047)。

摘　　要：土体的剪切模量是地基处理质检的主要力学指标之一。饱和砂土地基在地震作用下发生超静孔压上升和液化的现象,导致土体的剪切模量和地基承载力降低,震后随着孔压消散而逐渐恢复。这种地震液化过程中土体模量的变化对认识地基动力响应规律和评价地基承载力及变形具有重要意义,但在实际工程场地中很难被直接观测到。首先,本文在忽略振动引起土体结构性变化的假设下,根据有效应力原理和Hardin公式提出了饱和软弱土振动液化过程中小应变剪切模量预测方法;其次,开展了一组倾斜饱和砂土场地超重力振动台模型试验,监测了振动过程中模型地基的加速度、超静孔压和地表沉降响应,并利用高速相机和压电弯曲元波速测试系统实时采集砂土振动液化过程中的剪切波动信号,采用视频分帧识别技术获得不同时刻的剪切波速。研究表明,本文方法的剪切波速预测值与压电弯曲元实测值基本一致,振动过程中的饱和砂土小应变剪切模量随着超静孔压的累积而降低,振后又随孔压消散而逐渐恢复。本文研究可为振动作用下饱和软弱地基的刚度监测和检测提供科学依据。The shear modulus of soil is one of the primary mechanical indicators for quality check in ground treatment.The liquefaction of saturated sand ground may occur during earthquake,which results in the decrease of the soil stiffness and the ground bearing capacity.With excess pore water pressure gradually dissipating and effective stress increasing,the soil stiffness gradually recovers to the pre-earthquake level.The degradation of soil stiffness during soil liquefaction is of great importance to understand the dynamic responses of the liquefiable ground,as well as the bearing capacity and deformations of the ground.However,it is difficult to monitor the soil stiffness during shaking directly in engineering practice.In this study,based on the effective stress mechanism and Hardin’s equation,the prediction method of small-strain shear modulus of the saturated sand during cyclic loading was proposed.Centrifugal model test of inclined sand slope was carried out to monitor the acceleration,excess pore water pressure and settlement of the model ground during shaking.In addition,the piezoelectric bender element system and high-speed camera were used jointly to collect the triggering and receiving shear wave signals during shaking.The shear wave velocities at different moments were processed by video recognition technique.The test results show that the predicted shear wave velocity is in agreement with the measurements of piezoelectric bender elements.They both tell the fact that the small-strain shear modulus of saturated sand decreases with the accumulation of excess pore water pressure during shaking,and gradually recoveres with the dissipation of excess pore water pressure after shaking.This study provides a scientific basis for monitoring and detecting the stiffness of saturated soft soil foundations under seismic loading.

关 键 词：超重力离心模型试验 压电弯曲元 剪切波速 小应变剪切模量 实时监测 质检 

分 类 号：TU411[建筑科学—岩土工程]