基坑降水开挖对邻近群桩的影响及控制对策

Influence of dewatering and excavation of foundation pits on adjacent pile groups and its control measures

以武汉地铁2号线循礼门车站下穿轻轨桥墩段为依托,采用考虑流固耦合作用的三维数值模拟方法探讨了深基坑降水开挖对邻近桩基的影响规律,并对几种措施的位移控制效果进行了分析;然后着重论述了被动区加固参数对桩基位移的影响.结果表明:通过优化降水方案来控制邻近桩基变形的效果比较明显;隔离桩、主动区加固和被动区加固都能一定程度地抑制桩基的水平位移,相比而言,被动区加固的效果更佳;被动区加固深度存在临界范围,加固体所在深度与最大水平位移出现的深度一致为宜.

Based on the deep foundation pit of Xunlimen Station of Wuhan Metro Line 2, which under- neath passes the viaduct of Wuhan LRT （light rail transit）, a three-dimensional elastic-plastic numerical simulation model, in which the coupling effect of fluid-soil interaction was considered, was established. The influence of the dewatering and excavation of foundation pits on adjacent pile groups was calculated and analyzed. Then the effects of common control measures were compared. This numerical model was employed to analyze the influence laws of the parameters of the passive zone improvement on adjacent pile groups. The results show that it is an effective way to control the pile deformation by optimizing the dewatering scheme. The pile deformation can be also controlled in some degree by means of installing strengthening piles and improving the soil in the active zone and the passive zone. In contrast, the effect of the passive zone improvement is more significant than the other strengthe- ning measures. There is a critical value for the depth and modulus of the passive zone improvement, and the best controlling effect may be obtained when the position of passive zone improvement is consistent with that of the maximum horizontal displacement of the diaphragm wall.