软土深基坑单井回灌参数优化与现场测试分析

为解决因深基坑降水和基坑渗漏引起的地表沉降问题,通常在坑外进行地下水回灌,而回灌参数会影响地表沉降控制效果。为了选取合适的回灌参数,采用ABAQUS有限元程序进行滤管长度、回灌井井径、井深、回灌压力对地表沉降影响的敏感性分析,得到如下结论:回灌压力和回灌井井深为控制地表沉降的关键因素,对控制基坑周边的沉降变形相对敏感,在设计回灌井时应首先考虑;而滤管长度和回灌井井径对控制地表沉降变形不敏感。回灌压力越大,控制地表沉降的效果越好,但不能无限制增加回灌压力,应根据回灌井周围密封强度计算回灌压力上限值。回灌井越深,基坑周边地表沉降越小,但应结合地质条件选取合理的井深。将选取的回灌参数用于现场回灌试验,回灌后坑外地下水位明显抬升,有效地控制了基坑周边地表沉降。

Parameters Optimization and Field Test Analysis on Recharge Well in Deep Foundation Pit of Soft Soil

In order to solve the problem of surface subsidence caused by dewatering and seepage of deep foundation pit, the method of the groundwater recharge is usually carried out outside the pit, and the parameters of recharge will affect the effect of surface subsidence control. In order to select suitable recharge parameters, ABAQUS finite element program was used to analyze the influence of filter tube length, recharge well diameter, well depth, and the recharge pressure on surface subsidence. The following conclusions are drawn: the recharge pressure and the recharge well depth are the key factors to control surface subsidence, and they are relatively sensitive to control settlement and deformation around foundation pit. These two factors should be considered first in designing recharge wells. The length of filter tube and the diameter of recharge wells are not sensitive to controlling surface subsidence and deformation. The greater the recharge pressure, the better the effect of controlling surface subsidence, but the recharge pressure can not be increased indefinitely. The upper limit of recharge pressure should be calculated according to the sealing strength around the recharge well. The deeper the recharge well is, the smaller the surface settlement around the foundation pit is, but the reasonable depth should be selected according to the geological conditions. The selected parameters of recharge were used in the field recharge test. After recharge, the groundwater level outside the pit rose obviously, which effectively controled the ground settlement around the pit.