特大暴雨引起的深基坑变形分析及降水处理

Deformation Analysis and Dewatering Treatment of Deep Foundation Pit Caused by Heavy Rain

降雨通常易导致土体力学性质变化,进而影响基坑的安全性,尤其是在强降雨情况下。以受郑州7.20暴雨影响较大的郑州地铁小南岗站深基坑工程为背景,结合降雨期内工程实测数据,采用MIDAS有限元软件进行分析,以揭示短时特大暴雨导致的地铁深基坑变形的关键因素,分析基坑满蓄水情况下的降水处理方法,并提出基坑工程面对特大暴雨时的一些防范措施。结果表明:特大暴雨影响地铁深基坑的关键因素是内支撑脱落及基坑回灌水的作用,其中内支撑脱落主因是基坑回灌降低了围护结构两侧的水土压力差,从而削弱了围护变形;对满蓄水基坑进行降水时,宜采用基坑内外联合降水的方法,并及时施作钢支撑;面对特大暴雨,应及时加高挡土墙,加固钢支撑与围檩的连接。

Precipitation can alter soil mechanical properties and affect excavation safety,particularly during periods of high precipitation.This study is based on the"7.20"rainstorm that occurred in Zhengzhou,Henan Province.A deep foundation pit of"xiaonangang"station of Zhengzhou was taken as a case study,and MIDAS finite element software was adopted to analyze engineering data measured during rainfall.This work also reveals the key factors of subway deep foundation pit deformation caused by short-term exceptionally heavy rainfall,analyzes the method of precipitation handling in the case of fully storing water in the foundation pit,and proposes some precautionary measures for the foundation pit project facing exceptionally heavy rainfall.The results are as follows.The main factors of the extra heavy rain affecting the deep foundation pit of the subway are the dislocation of the internal support and the role of pit filling,of which the main reason for the dislocation of the internal support is that the pit filling reduces the difference between the soil and water pressure on both sides of the enclosing structure,thus weakening the deformation of the enclosure.When descending the full storage pit,it is appropriate to use the method of joint descending of both the inside and outside of the pit,and timely apply steel support;In the face of extra heavy rain,the steel support should timely raise retaining wall and strengthen the connection between steel support and walings.