天津地铁基坑降水工程地下水越流特性

Characteristics of groundwater leakage in dewatering engineering of Metro foundation pit in Tianjin City

天津位于地下水位较高的软土地区,地下潜水的流失对地表及建(构)筑物沉降影响较大,而承压水对工程威胁较大且对沉降影响形式与潜水不同,因此在基坑开挖前摸清各层地下水的水力联系、渗透系数和含水层涌水量等是至关重要的。本文结合天津地铁4个站点的工程实例,深入分析了地铁工程基坑降水过中所产生的地下水越流特点,基于基坑开挖前的降水试验结果,建立三维渗流模型预测长时间降水对基坑周边地下水水位的影响,并与现场实测结果进行对比,结果比较吻合,其数据基本上反映了在目前止水帷幕设计条件下,正式开挖状况下的降水(减压)规律,对判断环境影响和制定应急预案有指导价值。

Tianjin is in a soft soil area with high groundwater level,and the loss of unconfined water has a great influence on the settlement of the surface and structures.The confined water has a great threat to the project and its influence on settlement is different from that of the unconfined water.Therefore,it is very important to find out the hydraulic relationship,permeability coefficient and water inflow of aquifer before the excavation of foundation pit.Based on the engineering examples of four stations in Tianjin subway,the characteristics of groundwater overflow caused by the dewatering in the foundation pit of the Metro project are analyzed.Based on the dewatering test results before the foundation pit excavation,a three-dimensional seepage model to predict the influence of the long-time dewatering on groundwater level around foundation pit is established,and compared with the field measurement results.The results are consistent,and the data basically reflect the law of the dewatering(decompression)of foundation pit under the condition of the formal foundation pit excavation and under the current design condition of the water-stop curtain,which has the guiding values for judging the environmental impact and formulating the emergency plans.