软土区管廊基坑柔性支护下基坑变形控制标准

软土区基坑工程中,控制基坑变形十分重要。本文对广州南沙柔性支护的管廊基坑进行有限元分析,得到了开挖过程中基坑的变形特征,开挖到基坑底部时,围护结构桩身变形由“悬臂式”变为“内凸型”,围护结构达到最大水平位移值31.92mm；地表沉降与坑底隆起最大值为22.26mm、54.81mm；稳定性计算结果为2.2,基坑变形及稳定性均满足规范要求。继而研究了6个不同基坑断面在临界失稳状态与稳定性满足规范这两种条件下,围护结构水平变形、地表沉降、坑底隆起的变形最大值占基坑开挖深度的百分比,建议将计算结果的平均值作为控制值的参考值。基坑临界失稳状态下,设计安全等级为二级、三级的基坑围护结构水平变形控制参考值分别为基坑深度的2.62%、3.24%。基坑稳定性满足规范要求时,设计安全等级为二级、三级的基坑围护结构水平变形控制参考值分别为基坑深度的0.8%、0.93%。

Research on deformation control standard of pipe gallery excavation with flexible retaining structure in soft soil area

For the excavation in the soft soil area, it is very important to control the deformation. In this paper, the finite element analysis of the pipe gallery excavation with flexible retaining structure in Nansha, Guangzhou is carried out. The deformation characteristics of the excavation during the excavation process are obtained. When excavating to the bottom, the maximum horizontal displacement value of the retaining structure reaches 31.92mm, the maximum value of surface settlement and basal heave is 22.26mm and 54.81mm, the stability calculation result is 2.2, whose deformation and stability meet the requirements of the specification. Then, under the two conditions of critical instability state and stability meeting the specification for 6 different excavation sections, the maximum deformation value of the retaining structure horizontal deformation, surface settlement and basal heave accounted for the percentage of the excavation depth. It is recommended to use the average of the calculated results as a reference value for the control value. Under the critical instability state, the reference values ??for the horizontal deformation control of the retaining structure with the design safety level two and three are 2.62%H and 3.24%H, respectively. When the stability of the excavation meets the requirements of the specification, the reference values ??for the horizontal deformation control of the retaining structure with the design safety level two and three are 0.8%H and 0.93%H, respectively.