临江富含承压水深基坑减压降水现场试验研究

In-Site Test Research on Depressurization Dewatering of Deep Foundation Pit with Rich Confined Water along the River

摘要: 对于临江富含承压水的深基坑，选择合理可行的减压降水方案是深基坑顺利施工的关键。本文依托中俄东线长江盾构隧道工程，通过抽水试验获取承压含水层水文地质参数，采用数值法对比分析了止水帷幕进入含水层不同深度条件下，坑外降水、坑内降水基坑总涌水量的变化规律。结果表明：随着止水帷幕深度递增，坑外、坑内降水水量之比随之增加；坑外井滤管与墙底平齐时，由于坑内下部存在强补给，坑外、坑内降水水量之比约34，表明坑外降水代价巨大；止水帷幕进入承压含水层仅几米时，坑内降水也有明显优势；若需要坑外降水时，降水井滤管深度须超过止水帷幕深度。研究成果可为类似临江深基坑降水设计提供参考。

Abstract: Regarding deep foundation pits along the river with rich confined water, one of the keys is how to choose a reasonable and feasible decompression and dewatering plan to benefit the smooth construction of deep foundation pit. In this paper, based on the Sino-Russian Eastern shield-driven tunnel project to cross Yangtze River, the hydrogeological parameters of the confined aquifer are obtained by pumping tests. And numerical method is used to analyze the total water inflow of the foundation pit for dewatering outside the pit and dewatering inside the pit when the water-stop wall enters the aquifer at different depths. The results show that as the depth of the water-stop wall increases, the ratio of dewatering inflow outside and inside the pit increases fairly. However, when the filter tube of the well outside the pit is flush with the bottom of the wall, due to the strong replenishment in the lower part of the pit, the ratio of the water inflow for dewatering outside to the inside the pit is about 34, which means the cost of dewatering outside the pit is huge. Even if the water-stop wall is only a few meters into the confined aquifer, dewatering in the pit also has obvious advantages. If dewatering outside the pit is required, the depth of the filter tube of the dewatering well must exceed the depth of the water-stop wall. The results can provide a reference for the dewatering design of similar deep foundation pits along the river.