基坑土体侧向卸荷变形特性的研究

Deformation Characteristics of Foundation Pit Soils under Lateral Unloading

利用GDS三轴仪对深基坑周边主动区粉质黏土进行了平面应变条件下的k0固结侧向卸荷试验和常规三轴压缩试验,试验结果表明:两种应力路径试验的应力–应变关系曲线均呈双曲线型,均表现为非线性,且全部呈应变硬化现象;卸荷破坏主应力差均小于加载破坏主应力差。针对卸荷产生的侧向应变采用有限元软件模拟土样的侧向卸荷,确定了粉质黏土Δε22和Δε32之间的比例范围,进一步推导出侧向卸荷条件下切线弹性模量的计算公式。

The ko consolidation - lateral unloading plane strain experiment and conventional triaxial expen- ment are made with the GDS triaxial apparatus using the silty clay from a deep foundation pit peripheral active area. The results show that ： the stress - strain curves of two stress paths tests are similar to a hyperbolic type ; they are non-linear and show the phenomenon of strain hardening, the principal stress difference of unloading test is less than that of loading test. For the lateral strain generated by the unloading test, the finite element software is used to simulate lateral unloading test. The ratio between △ε22 and △ε32 of the silty clay is determined. The expression of tangent modulus of the silty clay under lateral unloading is further deduced.