城市轨道交通地下车站深基坑降水设计施工探讨

Discussion on Precipitation Design and Construction of Deep Foundation Pit of Urban Rail Transit Underground Station

福州市轨道交通地下车站设计多采用明挖深基坑,地质多以砂层、淤泥质土等软土地层为主。深基坑开挖范围内多遇砂层、淤泥质土层及全风化花岗岩等地质渗透性能差异较大的地层上下错开分布,当地下水位出现异常时会导致潜水与承压水汇流。深基坑开挖过程中坑内外出现较大的水头差极易产生围护结构流砂、管涌和基底突涌等渗漏破坏事故,最终导致开挖边坡或基坑失稳,造成周边地表沉降,严重时会影响周边道路、建(构)筑物的安全。本文以福州市城市轨道交通某高富水厚砂层地下车站深基坑降水为例,总结本工程深基坑降水设计方式及参数选择和现场施工经验,为类似地质的城市轨道交通地下车站的降水工程施工提供参考的技术参数和施工工法。

The design of underground railway stations in Fuzhou City mostly adopts open-cut deep foundation pits,and the geology is mostly sandy,silty soil and other soft soil layers.In the excavation area of deep foundation pits,there are often sand layers,silty soil layers,and fully weathered granites that are staggered up and down.When the local water level is abnormal,it will cause the confluence of phreatic water and confined water.During the excavation of deep foundation pits,there is a large difference in water head between the inside and outside of the pit.It is easy to cause leakage and damage accidents such as quicksand,piping and base surge of the containment structure,which will eventually lead to instability of the excavation slope or foundation pit,resulting in surrounding surface settlement.In severe cases,it will affect the safety of surrounding roads and buildings(structures).This paper takes the precipitation of a deep foundation pit of an underground station with high water-rich and thick sand layer in Fuzhou urban rail transit as an example,summarizes the precipitation design method and parameter selection of the deep foundation pit of this project and on-site construction experience,providing referential technical parameters and construction methods for the construction of precipitation engineering of urban rail transit underground stations with similar geology.