降水井错位布置对基坑预降水引发围护结构侧移的影响

Behavior of retaining wall during dewatering before soil excavation under layout of staggered wells

基坑开挖前预降水是富水地层中深基坑施工的一项重要施工步骤,其引起的围护结构及周边地层变形可以达到cm级。然而,传统基坑设计理论与相关研究未提出基坑预降水引发基坑变形的控制方法。本文提出了一种降水井错位布置的方法用于控制预降水引起的围护结构变形,指出可使距离围护结构越近的降水井相对越深、相邻降水井间距相对越小。数值计算结果表明,这种方法相对于常规抽水方式(等间距等长布置降水井,同时或随意开启)而言,可以改变预降水过程中坑内渗流场分布,使得在围护结构附近出现指向围护结构的渗流迹线,从而限制了预降水过程中背离围护结构的坑内土体水平位移的发展,最终起到减小围护结构侧移的作用。若合理地对降水井进行错位布置,可较大程度限制基坑预降水引发围护结构的侧移。

The dewatering conducted before soil excavation is an important stage in deep excavation.This dewatering construction is proved to be able to induce considerable deflection of retaining wall.However,how to control this type of deformation has not been proposed.A method called layout of staggered wells is proposed to control the dewatering-caused wall deformation.In this method,the uniformly-spaced and uniformly-buried layout of wells(i.e.,the conventional layout of dewatering wells in practical engineering)is not advocated.It is recommended that(1)deeper wells should be employed near the retaining structures,and when the distance to the retaining structures increases,the wells depth should decrease gradually,and(2)smaller spacings of neighboring wells should adopted near the retaining structures,and when the distance to the retaining structures increases,the spacings of neighboring wells increase gradually.The numerical results show that the proposed method can lead to a smaller seepage flow velocity around the wall.Hence,the horizontal deformation of soil induced by seepage force will be relatively smaller,which eventually limit the deformation development of the retaining structures.