悬挂式止水帷幕基坑降水控制措施研究

为了优化深基坑降水控制技术,以天津某地铁换乘站基坑降水为背景,利用有限差分软件Visual Modflow,对基坑开挖降水引起的基坑内外地下水水位变化进行数值模拟计算,模拟计算结果与监测数据基本吻合。同时,在此模拟计算基础上对止水帷幕插入深度、降水井的抽水速率、滤水管插入承压含水层深度及降水时间等几种控制措施在降水控制中所发挥的作用进行深入研究。结果表明,降水过程中止水帷幕深度插入比宜达到1:0.9～1:1之间,滤水管插入承压含水层深度宜控制在0.5～0.7倍含水层厚度区间范围内,降水井抽水速率的大小需根据以上两种措施确定后再进行优化。此研究结果不但能有效减少基坑降水对周围环境的影响,还能保护地下水资源,节约工程造价。

Research on Control Measures Unclosed Curtainfor Cutting off Drains on Dewatering of Foundation Pit

In order to optimize the control technology of deep foundation dewatering,taking a foundation pit dewatering engineering of a subway transfer station in Tianjin,the numerical simulation was conducted by using finite differential code Visual Modflow to calculate the change of groundwater level of inside and outside foundation pit due to dewatering in deep excavation.The numerical results were consistent with actual monitoring data.At the same time,the role of several control measures such as the depth of curtain for cutting off drains,pumping rate of dewatering wells,depth of filter tube into the confined aquifer and pumping time in the dewatering process of foundation pit were deeply studied based on the above simulation calculation.The results showed that the insertion ratio of curtain for cutting off drains is 1:0.9-1:1 during foundation dewatering for proper,and the insertion depths into confined aquifer of filter tube should be controlled with a range within 0.5-0.7 times of the confined aquifer thickness.The pumping rate of dewatering wells should be optimized in accordance with the two measures above.This research results can not only minimize the influence of surrounding environment during the foundation dewatering,but also protect the groundwater resources and decrease the construction cost.