土钉墙支护及其应力特征数值模拟分析——以长沙中建梅溪湖项目基坑支护为例

Numerical Simulation Analysis of Soil Nailing Wall Support and Its Stress Characteristics—Taking the Foundation Pit Support of Meixi Lake Project of Changsha Zhongjian as an Example

摘要: 本文以长沙中建梅溪一号(3B地块)基坑工程为例，通过前期的地质调查、多方案论证，确定了初步的土钉墙支护结构和放坡挂网素喷的基坑支护方案，应用FLAC3D对支护方案模拟，模拟分析了采用土钉墙支护条件下，基坑开挖过程中基坑土体的应力场分布规律、支护结构受力状况，模拟结果显示：1) 从土钉受力情况来看，土钉轴力基本为拉力。同时，随着开挖工程的开展，土钉受力情况是随之而发生变化的，数值模拟结果显示，开挖过程中，土钉所承受的最大轴力为5.2 t。2) 土钉在长度方向上轴力分布遵循“中性点”原则，即中间数值大、两边数值小。最大轴力位置在潜在滑移面处。靠近坡面土钉段的轴力大于土钉深部段轴力这说明，土钉除了承受土体变形后施加的动力外，还受到喷射混凝土面层施加在土钉上的抗拔力作用。3) 随着开挖的进行，土钉受力逐渐增大。这主要是由于开挖深度增加，基坑边坡土体变形增加，将土体的位移力和土体膨胀力传递给土钉所致。

Abstract: In this paper, taking the foundation pit project of No. 1 Meixi (3b block) of Changsha Zhongjian as an example, through the preliminary geological investigation and multi scheme demonstration, the preliminary soil nailing wall supporting structure and the foundation pit supporting scheme of sloping hanging net and plain spraying are determined. The FLAC3D is used to simulate the supporting scheme, and the stress field distribution rule and supporting structure of the foundation pit soil during the excavation are simulated and analyzed. The results show that: 1) The axial force of soil nail is tensile force. At the same time, with the development of excavation engineering, the stress of soil nails changes accordingly. The numerical simulation results show that the maximum axial force of soil nails is 5.2 t. 2) The axial force distribution of soil nail in the length direction follows the principle of “neutral point”, that is, the middle value is large and the two sides value is small. The maximum axial force is located at the potential slip surface. The axial force of the soil nail near the slope is greater than that of the deep part of the soil nail, which indicates that the soil nail is not only subjected to the force exerted by the deformation of the soil, but also to the pull-out force exerted by the shotcrete surface on the soil nail. 3) With the progress of excavation, the stress of soil nail increases gradually. This is mainly due to the increase of excavation depth and soil deformation of foundation pit slope, which transfers the displacement force and expansion force of soil to soil nails.