沿江地铁车站基坑支护结构的设计与实测研究

The Research on Design and Field Measurement for the Retaining Structure of Excavation of Along-river Metro Station

沿江地铁车站基坑两侧地形不对称,存在较为明显的偏压效应,对围护结构受力性状产生较大影响。以福州地铁5号线农林大学站基坑工程为依托,利用FLAC^(3D)平台对其开挖与支护全过程进行数值模拟,探讨基坑支护结构的整体偏移规律及基坑两侧围护墙背土压力分布规律。数值模拟结果表明,地形不对称导致的偏压荷载,使得支护结构整体向闽江一侧发生偏移,其最大偏移量可达27mm。相应地,基坑两侧围护墙背土压力存在明显差异,尤其是基坑中下部区域,靠山侧土压力整体比沿江侧偏大30%~50%。同时,施工期间围护墙水平位移和支撑轴力的实测数据,也验证了上述支护结构的施工力学特性。若将第3道支撑改为常规钢支撑,围护墙整体偏移量和倾覆角度明显增大,可见混凝土支撑能有效增强支护结构的整体性,尤其在依山沿江不对称地层条件下是十分必要的。

For the metro station along river,the asymmetric ground pressure due to terrain bias could influence the construction mechanism of retaining and protection structure significantly.Based on the excavations of Nonglin University Station in Fuzhou Metro Line 5,the excavating and propping processes are simulated on the numerical platform FLAC3D.The overall deviation of retaining structure and soil pressure distribution on retaining structure are discussed in detail.The simulation results show that the asymmetric ground pressure due to terrain bias shifts the retaining structure overall towards the river side,and the maximum deviation reaches 27 mm.Meanwhile,the soil pressures on two sides of retaining structure are quite different from each other.Especially,within the medium and deep range of foundation pit,the soil pressure on the mountain side is 30%~50%higher than that on the river side.The monitoring data on the lateral displacement of retaining wall during the construction show the similar mechanism as presented above.If the 3 rd concrete shoring is changed to steel-pipe shoring,the overall deviation and inclined angle of the retaining structure would increase significantly.Therefore,the design of 3 rd concrete shoring could enhance the integrity of the retaining structure,which is very important in case of asymmetric ground condition along mountain and river.