桩锚支护体系深基坑开挖的数值模拟分析

Numerical Simulation Analysis of Deep Foundation Pit Excavation for Buildings with Pile-Anchor Support

为预判基坑开挖中可能出现的危险工况,以合理选择基坑支护类型,研究随基坑开挖深度增加时,桩锚支护体系下深基坑的变形与锚索受力变化规律。以实际工程为例,运用MIDASGTSNX有限元软件构建二维基坑模型,对桩锚支护基坑开挖过程中不同工况下的坑底隆起、地表沉降、围护桩顶水平位移及锚索的轴力变化进行数值模拟分析。结果表明:随着开挖深度增加,周围土体产生“挤土效应”,当开挖至坑底时基坑隆起量达最大,为15.4mm;不同工况下地表最大沉降量先减小后增大,地表沉降曲线呈“勺”型;桩顶最大水平位移与开挖深度成正相关;随着开挖深度增加,第二道锚索轴力增长速度远大于第一道锚索。

To predict the danger in the excavation of foundation pit,the type of foundation pit support is properly selected,and a study is conducted on the deformation of deep foundation pit with the increase of excavation depth in the foundation pit,and the law of force change on the anchor cable under the pile-anchor support.Taking a deep foundation pit project in Shenzhen as a case,the MIDAS GTS NX geotechnical finiteness software is used to build a two-dimensional foundation pit model.The bottom uplift,surface settlement,horizontal displacement of the retaining pile top and the axial force change of the anchor cable under different working conditions during the excavation are numerically simulated and analyzed.The results show that with the increase of excavation depth,the surrounding soil produces“soil squeezing effect”,and the uplift of foundation pit reaches the maximum of 15.4 mm when excavated to the bottom.Under different working conditions,the maximum surface settlement first decreases,then increases,forming a spoon-shaped curve.The maximum horizontal displacement of pile top is proportional to the excavation depth.With the increase of excavation depth,the axial force of the second anchor cable grows much faster than that of the first anchor cable.