折线应力路径条件下粉质黏土力学特性试验研究  

Experimental Research on Mechanical Properties of Silty Clay Under Broken Line Stress Path Condition

作　　者：刘连栋 刘燕[1,2] 李春林 张亮亮[4] LIU Liandong;LIU Yan;LI Chunlin;ZHANG Liangliang(School of Civil Engineering and Architecture,University of Jinan,Jinan 250022,Shandong,China;The Engineering Technology Research Center for Urban Underground Engineering Supporting and Risk Monitoring of Shandong Province,University of Jinan,Jinan 250022,Shandong,China;Jinan City Construction Group Co.,Ltd.,Jinan 250131,Shandong,China;China Railway Siyuan Survry and Design Group Co.,Ltd.,Wuhan 430063,Hubei,China)

机构地区：[1]济南大学土木建筑学院,山东济南250022 [2]济南大学山东省城市地下工程支护及风险监控工程技术研究中心,山东济南250022 [3]济南城市建设集团有限公司,山东济南250131 [4]中铁第四勘察设计院集团有限公司,湖北武汉430063

出　　处：《济南大学学报（自然科学版）》2024年第1期23-28,共6页Journal of University of Jinan(Science and Technology)

基　　金：国家自然科学基金项目(51979122);山东省自然科学基金项目(ZR2022ME042)。

摘　　要：为了探究先基坑开挖后坑边大吨位吊装的特殊应力路径条件下粉质黏土的变形规律、孔压变化以及强度指标,以济南市某隧道附近的粉质黏土原状土样为研究对象,采用K0固结先侧向卸荷后轴向加荷不排水剪切试验,并在卸荷阶段选取3个不同的卸荷比,模拟先基坑开挖后坑边大吨位吊装特殊工况下的应力路径,然后进行等压固结不排水常规三轴剪切试验和K0固结侧向卸荷不排水剪切试验,并对比3种试验结果。结果表明:先基坑开挖后坑边大吨位吊装的特殊应力路径条件下的偏应力-轴向应变试验曲线为非线性曲线,粉质黏土的破坏强度与卸荷量有关,卸荷量越大,则破坏强度越小;减围压阶段产生负孔压,轴向加压阶段孔压随着轴向应变的增加呈先增大后减小的趋势,在同一初始固结围压下,粉质黏土的卸荷比越小,则剪切时产生的最大孔压越大;先基坑开挖后坑边大吨位吊装的特殊应力路径条件下粉质黏土的卸荷比越大,则有效黏聚力越大,有效内摩擦角越小,与等压固结不排水常规三轴剪切试验相比,有效内摩擦角偏小,有效黏聚力随卸荷比的不同而偏大或偏小。To explore deformation law,pore pressure variation,and strength index of the silty clay under the special stress path condition of foundation pit excavation first and large tonnage hoisting at foundation pit side then,taking silty clay undisturbed soil samples near a tunnel in Jinan city as research objects,K 0 consolidation undrained shear test with lateral unloading followed by axial loading was adopted and three different unloading ratios were selected during the unloading stage to simulate the stress path under a special condition of foundation pit excavation first and large tonnage hoisting at foundation pit side then.Isobaric consolidated undrained conventional triaxial shear test and K 0 consolidated lateral unloading undrained shear test were then carried out,and the three experime ntal results were compared.The results show that deviatoric stress-ax ial strain test curves under the special stress path condition of foundation pit excavation first and large tonnage hoisting at foundation pit side then are nonlinear curves.The failure strength of silty clay is related to the u nloading amount.The greater the unloading amount is,the smaller the failure strength is.Negative pore pressure is generated in reducing confining pressure stage.Pore pressure first increases and then decreases with the increase of axial strain in axial applying pressure stage.Under the same initial consolidation confining pressure,the small the unloading ratio of silty clay is,the greater the maximum pore pressure generated in shear is.Under the special stress path condition of foundation pit excavation first and large tonnage hoisting at foundation pit side then,the greater the unloading ratio of silty clay is,the greater the effective cohesion is and the smaller the effective internal friction angle is.Compared with the isobaric consolidated undrained conventional t riaxial shear test,the effective internal friction angle is smaller,and the effective cohesion is larger or smaller according to different unloadin g ratios.

关 键 词：土工试验 应力路径 三轴试验 粉质黏土 吊装荷载 

分 类 号：TU411.3[建筑科学—岩土工程]