考虑软土低应变性态的深基坑变形分析

Deformation Analysis of Deep Excavation Considering Small-strain Behavior of Soft Soil

由于土体的低应变性态对深基坑施工引起的变形问题影响显著,采用常规三轴试验指标进行数值模拟得到的基坑变形一般较实测数据要大。采用最常用的摩尔库伦模型来描述软土的变形行为,以现场剪切波速试验来测定软土在低应变时的弹性模量,采用数值模拟方法研究了深基坑开挖引起的连续墙变形和地表沉降问题,研究结果表明:采用低应变强度指标(Es)得到的数值模拟成果要较采用常规三轴试验指标(E)得到的成果更符合现场监测成果;采用Es指标得到的地表沉降的最大值及出现位置与实测非常一致,但变形规律存在差异;采用Es指标得到的连续墙变形在坑底以上较实测值稍小,而以下则偏大。研究结论对软土深基坑变形的数值分析有一定的参考价值。

Because of obvious effect of clay behavior at small-strain levels on deformation of excavation, the result obtained by numerical simulation using parameters taken from traditional tri-axial tests is usually larger than that observed in the field. Using Mohr Coulomb model to describe behavior of soft soil, and shear wave field test to determine stiffness of soft soil at small-strain levels, a numerical analysis was carried out to predict lateral wall movement and surface settlement of deep excavation. The results show： the predictions by numerical analysis using small strain stiffness （Es） match better observations than those using stiffness { E } derived from traditional triaxial tests. The predicted maximum value of surface settlement and its location using Es is consistent with observed results, but the deformation regularity is different. The Es prediction of lateral wall movement above base of excavation is relatively smaller than observed results, but the value under base of excavation is larger than observed. This study can provide reference for numerical analysis of excavation responses in soft soil.