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对卸荷土体工程性质的认识是解决基坑开挖工程中问题的关键,港珠澳大桥连接线珠海拱北隧道处于海相软黏土地层,基坑开挖深度大,断面宽,研究该基坑土体在卸荷应力路径下的土体本构模型及其参数,对工程设计有着重要的意义。取现场土样,选定海相沉积的淤泥质土和可塑状粉质黏土作为研究对象,测定其K0值,采用应力控制式三轴仪,在围压100,200,400,600 kPa状态下进行K0排水固结,对固结完成的土样进行不同应力路径的卸荷试验,根据应力–应变关系曲线的非线性特征,采用邓肯张E–μ模型作为该基坑土体的本构模型,依照试验结果,分别确定邓肯张E–μ模型的8个基本参数,为基坑有限元分析提供重要依据。
The understanding of the nature of unloading soil engineering is the key to solve the problems in excavation of foundation pit. Gongbei Tunnel of Zhuhai-Zhuhai-Zhuhai-Zhuhai-Zhuhai Bridge is located in marine soft clay stratum. The depth of excavation is large and the section is wide. Soil constitutive model and its parameters under unloading stress path are of great significance to engineering design. The soil samples were taken, the silty soil and the plastic silty clay of the marine sediments were selected as the research object, the K0 value was measured, stress-controlled triaxial apparatus was used to carry out K0 drainage consolidation at confining pressure of 100,200,400,600 kPa, According to the nonlinear characteristics of the stress-strain curve, Duncan Zhang E-μ model is adopted as the constitutive model of soil in the foundation pit. According to the test results, Determine 8 basic parameters of Duncan Zhang E-μ model, which provides an important basis for the finite element analysis of foundation pit.