不同桩撑支护形式的地铁明挖车站基坑变形监测研究

Deformation Monitoring on Foundation Pit of Open Excavated Subway Station with Different Pile-steel Support Forms

为研究不同桩撑支护形式的地铁明挖车站的基坑变形规律,对北京地铁6号线二期2座采用直径800 mm围护桩+3道钢支撑支护形式,1座采用直径1 000 mm围护桩+2道钢支撑支护形式的明挖车站基坑变形监测数据进行分析。研究表明:(1)两种桩撑形式下的基坑外地表沉降、桩顶水平位移和桩体水平位移变化规律接近;(2)基坑外地表沉降、桩顶水平位移、桩体水平位移分别在0.15%H、0.1%H、0.15%H范围以内(H为基坑开挖深度);(3)直径1 000 mm围护桩+2道钢支撑支护形式下的基坑变形更小,同时针对盾构先行过站而后开挖车站基坑的工程,直径1 000 mm围护桩+2道钢支撑支护形式可在综合费用几乎不变的情况下显著缩短工期,因此可为今后类似工程提供借鉴。

In order to study the deformation rule of foundation pits of an open excavated subway station with different pile-steel support forms,the deformation monitoring data of foundation pits are analyzed for two subway stations with 800 mm di-ameter supporting piles and 3 layers of steel support,and one subway station with 1 000 mm diameter supporting piles and 2 layers of steel support.Some conclusions can be drawn:(1)The ground settlement outside of the foundation pit,the hori-zontal displacement of the pile top,the horizontal displacement of the pile body are similar under two forms of pile-steel support.(2)The ground settlement outside of the foundation pit,the horizontal displacement of the pile top,the horizontal displacement of the pile body are respectively in the range of 0.15%H,0.1%H and 0.15%H(H is the excavation depth of the foundation pit).(3)The deformation of the foundation pit with 1 000 mm diameter supporting piles and 2 layers of steel support is smaller.At the same time,in view of the case of shield tunnel excavation passing through foundation pit before foundation pit excavation,this pile-steel support form can obviously shorten the project duration in the case that the compre-hensive cost is almost constant.So this pile-steel support form could be used as a reference for future similar projects.