虽然防渗墙在基坑渗流场控制中应用广泛,但是人们对于防渗墙作用效果的认识仍有不足。以武汉市常见的二元结构地基为背景,概化建立建筑基坑渗流场的典型模型,通过数值模拟分析揭示了防渗墙的渗流控制作用规律;以此为基础,结合工程实践,开展了防渗墙应用的研究。研究成果显示落底式防渗墙对基坑渗流场具有显著的控制效果,但必须更加切实防止墙体出现缺陷,确保落底于可靠的防渗依托层之中;悬挂式防渗墙对基坑渗流场的控制作用效果随贯入度增加而得到有限的提升,应结合成本、工期、基坑排水量控制和基坑安全要求,综合研究确定合适的防渗墙贯入度;防渗墙与排水措施相配合才能形成有效的基坑渗流场控制体系,针对具体工程,需要在充分掌握地质条件、地表水文条件、邻近防洪工程、建筑物及其他设施等条件下,论证渗流控制方案,以达到保障基坑安全和有效控制对周边环境不利影响的综合效果。这些结论也可为地铁等市政工程基坑渗流控制提供借鉴。

Cut-off wall is widely used to control the seepage field for building’s foundation pit, but the efficiency of cut-off wall is not known very well. In the background of the common foundation of double layers in Wuhan of China, a model was set up for the seepage field around a typical building foundation pit. Through numerical simulation, the law of seepage field control for cut-off wall was revealed. Then the application of cut-off wall was discussed on the basis of the study results and engineering practices. It is pointed out that cut-off wall of closure type could control seepage field efficiently under the conditions that the cut-off wall is prevented from any defect and is extended into reliable stratum with low permeability. The seepage control efficiency can be promoted to limited extent for the cut-off wall of suspension type with higher penetration rate which should be set reasonably with the cost, duration, water discharge and safety being taken into account. An efficient seepage field control system must be formed by coordinating cut-off wall and drainage measures. The seepage field control system for a building foundation pit should be designed in consideration of adjacent buildings, flood control projects and other facilities in addition to geological and hydrological conditions. Then we can achieve the safety of foundation pit and control its adverse effect on environment. These conclusions are referential for the foundation pit of public works including metro engineering.