深厚透水性地层中大型深基坑降水方案设计探讨

Design of Dewatering Plans for Deep Excavation Pit in Thick Permeable Strata

结合南水北调中线工程中深厚透水性地层中深基坑的降水方案设计范例,对纯井点降水、截水法以及帷幕+排水法等深基坑降水方法的特点进行了分析。认为:①这3种方法均能达到有效降低基坑地下水位的目的,在方案比选时,要对不同方案的技术经济进行比较,选择经济合理、技术可靠的方案,既降低地下水位,又保证基坑边坡及环境安全;②方案设计时,应进行现场抽降水试验以获得准确的水文地质参数;③在工程施工中必须做好监测工作,发现问题及时采取补救措施,以保证工程安全。

The engineering characteristics of three foundation pit dewatering plans for the South-to-North Water Diversion Project are compared. The result manifests that the three plans, namely by well point dewatering, by seepage cut-off walls, and by grouting curtains are all feasible for large scale and deep excavation pits in deep permeable strata. During the project design, worksite dewatering test is recommended to obtain the accurate hydrogeology information. Moreover, the plans must be compared based on 3-D numerical calculation in terms of cost and technique to ensure the safety of the foundation pit slope and the environment. Safety monitoring is indispensible for making emergency measures in case of problems during the dewatering.