粉质砂土土钉墙水平位移与土钉轴力的FLAC3D研究

以物理模型土钉墙的破坏性试验获得的土体的基本参数和模型的尺寸为基础，应用FLAC3D软件建立土钉墙数值模拟模型。通过数值模型模拟基坑开挖与支护过程，并监测该过程中的土钉墙墙体沿深度方向水平位移情况和各层土钉的轴力变化情况以及它们之间的关系。支护过程结束后，在墙顶分级施加竖向荷载直至墙体产生较大变形，研究了土钉墙在超载状况下的工作状况以及破坏过程，并与物理模型土钉墙的破坏性试验结果进行对比。研究发现，开挖过程中墙体水平位移底部大于顶部，呈“勺形”分布；墙体水平位移最大处附近的土钉轴力也最大；粉质砂土土钉墙变形超过基坑开挖深度的4‰后，墙体的稳定性会极大降低；粉质砂土土钉墙没有下卧软弱层时，在地面超载作用下其破坏形式为体内破坏，表现为部分土体沿滑裂面向下滑动。

FLAC3D simulation of horizontal displacement and axial force of soil nailing in silty sand soil nailing wall

FLAC3D software is used to establish numerical simulation model of soil nailing wall based on the basic parameters and dimensions of the model obtained from the physical model of soil nailing wall destructive test. The excavation and supporting process of the foundation pit are simulated by the numerical model, the horizontal displacement along the depth direction of the wall and the axial force of each layer soil nailing as well as the relationships between them are monitored. After the supporting process, vertical loading are exerted on the coping until large deformation of the wall appears in order to study the working conditions and the damage process of the soil nailing wall under the overload conditions, then compared with the results from the destructive test of the physical model for soil nailing wall. The study results show that the bottom horizontal displacement of the wall during the excavation stage is larger than at top, and in a spoon-shaped distribution; soil nailing axial force in the vicinity of maximum horizontal displacement of the wall is also the largest. If deformation of silty sand soil nailing wall is more than 4 ‰ of excavation depth, the stability of the wall would reduce greatly. When there is no soft substratum under the silty sand soil nailing wall, under the overload on the ground, the destruction form is the damage in the wall, and shows that a part of the soil slids down along the slip face.