基于HSS模型与MCC模型的深基坑降水开挖变形分析

Deformation of deep foundation pits due to excavation and dewatering based on HSS model and Modified Cam-Clay Model

在施工过程中基础、隧道和基坑周围土体除少数区域发生明显塑性变形外,其他大部分区域土体均处于小应变状态(10-2%~10-1%)。本文采用PLAXIS和ABAQUS有限元软件,土体本构模型分别采用HS-Small模型和MCC模型,模拟基坑降水开挖,对基坑变形结果进行对比分析。结果表明,修正剑桥模型由于未能考虑土体小应变特性,基坑位移变形模拟结果相对HS-Small模型偏大,弯矩模拟结果偏小。在进行敏感环境下的基坑降水开挖问题的数值模拟时,应采用能考虑土体小应变特性的本构模型,如HSS模型。

It is found from field tests data that the stiffness properties of a wide range of soils at low levels of strain often encountered in practice except a limited extent around foundations,tunnels and excavations. To provide more insight into the influence of the stress strain behavior of soils at small strains on the deformation of foundation pit displacement due to excavations and dewatering,the finite element software ABAQUS and PLAXIS were used in this study. Meanwhile,Modified Cam Clay model and HSS model were adopted for the soil,respectively. The following conclusions can be obtained. The values of deformation gained from the former are much more than the corresponding values gained from the latter due to the features of the behavior of soils at small strains cannot be described by Modified Cam Clay model. But the bending moment gained from the former is smaller than the corresponding value obtained from the latter. It is show that soil constitutive model considered the characteristic of non-linear variation of soil stiffness at small strains should be selected for numerical analysis of deep excavations in close proximity to sensitive properties.