土钉加固基坑开挖性能的拉格朗日元分析

基于理想弹塑性本构模型的Mohr-Coulomb准则,运用岩土力学理论、快速拉格朗日元(FLAC3D)数值方法,考虑土钉的加固作用及土钉与土体的相互作用,模拟土钉支护施工过程。选择能够反映开挖特点的土体本构关系、开挖支护模拟过程和双弹簧土钉单元,建立数值分析方法。通过计算研究了土钉支护的工作机理、变形和受力性能,以及基坑的力学和变形响应。结果表明:(1)第4、5步开挖引起的土体扰动最大;(2)滑裂面附近剪应变增量梯度比较大,土钉长度范围内土体已经成为一个整体;(3)土钉轴力沿长度的分布是不均匀的,上部土钉轴力表现为中间大而两边小的规律;下部土钉呈现端头轴力最大,沿土钉方向逐渐减小。

Lagrangian Analysis on Excavation Properties of Soil-nailed Foundation Pit

Based on Mohr-Coulomb rule about ideal elasto-plastic constitutive model and rock and soil mechanics theory,the simulation on the excavation process of foundation pit reinforced with soil nail was carried out by using the numerical simulation technique of fast Lagrangian analysis of continua(FLAC3D),which considering the reinforcement effect of soil nail and the interaction between soil and soil nail.The soil constitutive law which can reflect the excavation characteristics of soil,the process of excavation and reinforcement simulation,and the double-spring elements used to simulate soil nail are chosen to establish a numerical calculation model.By calculating,the working principle,strain and stress performances of soil nail,as well as the mechanical and deformation responses of foundation pit are analyzed.The results of analysis show that,(1) the fourth and fifth excavation steps make the largest disturbance to the soil;(2) the incremental gradient of shear strain near slip plane is larger than that of other areas,with the reinforcement of soil nails the soil mass in the length of soil nails has become a whole;(3) the axial stress distribution of along the length of soil nail is asymmetrical,the magnitude of stress is larger in the middle of soil nails and is lower at the both ends of soil nails in the upside of foundation pit,but the larger axial stress is at the end of soil nails near the surface of foundation pit,and decreases along the bar of soil nails in the underside of foundation pit.