兰州地铁红砂岩基坑开挖监测与数值模拟分析

Monitoring and numerical simulation analysis of red sandstone foundation pit excavation of Lanzhou subway

以兰州市东方红广场地铁车站红砂岩深基坑为研究对象,对基坑开挖过程中围护桩位移和基坑周边地表沉降进行现场监测,并对实测结果进行分析;采用MIDAS GTS数值模拟软件,分别建立深基坑开挖支护和渗流分析的三维模型,对深基坑在开挖过程中的位移进行模拟计算.结果表明:桩的水平位移随桩体嵌入深度先增大后减小,整体呈“)”形前倾,坑周地表沉降在开挖完成后基本趋于稳定;最大位移均发生在第三道钢筋混凝土横撑设置之前,且位移的变化有明显的空间效应.两项模拟开挖过程中位移变化趋势基本相同,而考虑渗流作用的数值分析的位移结果偏大;孔隙水压力失衡引发的渗流作用在基坑开挖完成后达到最大.

Taking the red sandstone deep excavation at Dongfanghong square subway station in Lanzhou city as the research object,the displacement of the retaining piles and the ground settlement around the foundation pit during the excavation of the foundation pit are monitored on site,and the measured results are analyzed.Using the MIDAS GTS numerical simulation software,three-dimensional models for deep excavation support and seepage analysis were established respectively,and the displacement of the deep foundation pit during the excavation process was calculated.The results show that the horizontal displacement of the pile increases first and then decreases with the depth of the pile body emplacement,and the overall shape is“)”.The settlement of the surface of the pit is basically stable after the completion of the excavation.The maximum displacement occurs before the setting of the third reinforced concrete cross braces,and the displacement has an obvious spatial effect.The trend of displacement change of the two simulation is basically the same,but the displacement result of the numerical analysis considering the seepage effect is o larger.The numerical analysis result of the seepage shows:the seepage effect caused by the imbalance of pore water pressure reaches the maximum after the excavation of the foundation pit is completed.