无支撑两级基坑支护结构变形影响因素分析

为探究无支撑多级支护结构的不同设计参数对基坑变形的影响，以一个无支撑两级支护的粉质黏土深基坑为例，利用FLAC3D软件建立数值模型，并基于正交试验通过极差、方差分析，就两级支护间距、开挖比以及两级支护结构长度对支护结构位移的影响进行研究。主要结论如下:采用无支撑两级支护结构的粉质黏土深基坑，两级支护结构的顶部最大位移受两级支护间距和开挖比影响的敏感度较高两级支护结构位移之间存在“叠加作用”、“牵引作用”的相互影响，但当两级支护间距不小于总开挖深度的0.5倍时，相互影响不显著当两级支护间距不小于总开挖深度的0.5倍，且开挖比为0.8~1.3时，两级支护结构的顶部最大位移比较接近，且不超过规范的一级基坑下限控制值，处于最合理的工作状态。

Analysis of influencing factors on deformation of retaining structures of unsupported two-stage foundation pits

This study aims to explore the influence of different design parameters of the unsupported and multi-stage retaining structure on the deformation of the foundation pit. With an unsupported two-stage silty clay deep foundation pit as an example, a numerical model was established by using FLAC3D software. Based on the orthogonal experiment, the influence of the distance between the two-stage support, the excavation ratio and the length of the two stages of retaining structure on the displacement of the support structure is studied through the range and variance analysis. Results show that the maximum displacement of the top of the two stages of retaining structure is highly sensitive to the influence of the distance between the two stages of retaining and the excavation ratio for the silty clay deep foundation pit with unsupported two-stage retaining structure. There are mutual influences between the displacements of the two stages of retaining structure, such as “overlay effect” and “drag effect”, but when the distance between the two stages of retaining is not less than 0.5 times the total excavation depth, the mutual influence is not significant. When the distance between the two stages of retaining is not less than 0.5 times the total excavation depth and the excavation ratio is 0.8 ~ 1.3, the maximum displacement at the top of the two stages of retaining structure is close and does not exceed the lower limit control value of the primary foundation pit in the specification, so it is in the most reasonable working condition.