富水软土地层深基坑支护结构性状研究

Study on Characters of Supporting Structure for Deep Foundation Pit in Richwater Soft Stratum

研究目的:上海地铁内江路站紧邻黄浦江,站位所处地层主要为流塑状淤泥质黏土,地下水位埋深约1 m,地质条件极差。研究该地铁车站深基坑支护结构的内力、变形特性,对类似工程建设具有一定的参考价值和指导意义。研究结论:以该车站主体深基坑工程为背景,阐述了采用SAP84有限元程序对叠合墙和内支撑组成的支护体系进行增量法计算的过程,研究了基坑施工过程中围护结构水平位移、内支撑轴力、立柱隆沉以及坑外房屋建筑沉降的变化规律。监测结果显示:地下连续墙水平位移实测值约44～71 mm,大于计算结果;钢管支撑实测最大轴力值约占计算最大轴力的64%～80%;立柱最大隆起值约20 mm。实测数据分析表明:基坑施工时,尽量减少超挖,及时安装支撑,尽早浇筑垫层及底板混凝土,减少坑底土体暴露时间,能有效减小围护结构变形和周边建筑物沉降。

Research purposes： The Neijiang Road Station of Shanghai metro is closed to the Huangpu River, with the poor engineering geological conditions, such as flowing mucky clay and lm deep underground water. It is necessary to do the research on the internal forces and deformations of the supporting structure for the deep foundation pit of this metro station for providing the references to the similar works. Research conclusions： Taking the main deep foundation pit of this station as the engineering background, the introduction is given to the calculation process of the incremental method for the laminated wall and the internal bracing system by using the SAP84 finite element program. The research is done on the horizontal displacement of the underground diaphragm wall, the axis force of the steel bracing system, the vertical displacement of laced column and the settlement of the surrounding buildings during the excavation. The monitored result shows the measured horizontal displacements of the underground diaphragm wall are 44 - 71 mm, a bit bigger than the calculated values. The maximum measured axial forces of the steel bracing are about 64 to 80 percent of the maximum calculated value. The maximum heave value of the laced column is about 20mm. The analytical results indicate the deformation of retaining structure and the settlement of surrounding buildings can be effectively controlled if the steel bracing are installed in time and the floor concrete is casted as soon as possible.