承压水隔层对某地铁车站基坑降水效果的影响

利用离心模型试验、Biot固结理论的有限元和现场观测数值相结合的方法,对上海地区⑤-2层浅承压水和⑦层深承压水间的⑥层隔水层的存在或缺失对基坑变形和降水影响的研究表明,承压水隔层将对基坑开挖时的变形产生较大的影响。基坑开挖深度14．4～18 m、承压水位降低4 m 以内、承压水隔层厚度为5．8 m时,承压水隔层缺失将导致地表沉降最大值增加10％～20％,连续墙墙脚水平位移、基底最大隆起增加30％左右。基坑开挖较深时,不能用单一的抗突涌安全系数来控制承压水的降低程度;当承压水隔层缺失时,深层承压水降对浅层承压水位、地面沉降有影响,但影响主要发生在后期。

Influence of Separation Layer on Foundation Pit Dewatering

This paper is mainly concerned with the foundation pit deformation due to dewatering and excavation, in which a separation layer between two layers of confined water exists or not. The results of a centrifuge test and numerical analysis indicate that the existence of separation layer will cause a smaller foundation pit deformation compared with the case without it. If the foundation pit is deep enough, a uniform safety coefficient of piping shouldn' t be used. Dewatering of deep confined water will reduce the water level of upper layer and induce deformation of soil, but it will often occur at the late period of dewatering.