地铁明挖区间深浅基坑永临结合支护技术研究

Study on Permanent-temporary Combined Support Technology for Deep and Shallow Pit in Open Cut Tunnel of Subway

某地铁明挖区间深基坑工程中,轨道正线与出入场线共用基坑,由于两基坑功能不同,其底部存在较大高差。通过在深浅基坑过渡时设计排桩支护,桩顶施作钢筋混凝土冠梁,并在浅坑钢筋混凝土底板内设置横向暗梁,将冠梁与地下连续墙连接锚固,形成框架结构,其中部分支护结构永临结合;同时在深浅坑基底分别设置钻孔灌注桩,并对浅坑基底进行水泥搅拌桩加固,改变土体力学性能,以提高基底强度及结构的抗倾覆能力。监测数据分析结果表明,基坑周围土体各技术参数稳定,变化值在允许范围内,该技术有助于解决深浅基坑支护方面的难题。

In a deep foundation pit of open cut tunnel of a subway,the main line of the track is shared with the entrance and exit line of the foundation pit,due to their different functions,there is a large height difference between the bottom of the two foundation pits.Through the design of row pile support during the transition of deep and shallow foundation pit,the reinforced concrete crown beam is applied at the top of pile,and the transverse concealed beam is set in the bottom plate of shallow pit,the crown beam is connected and anchored with the diaphragm wall to form a frame structure,some of the supporting structure is permanent-temporary combined;and bored piles are respectively installed in the foundation of deep and shallow pit,and cement mixing piles are used to reinforce the foundation of shallow pit,so as to change the mechanical properties of soil,to improve the strength of the base and the anti-overturning ability of the structure.According to the analysis of monitoring data,it is shown that the technical parameters of soil around foundation pit are stable and the changing values are within the allowable range,this technology is helpful to solve the problems of deep and shallow foundation pit support.