Tianjin Institute of Geotechnical Investigation �� Surveying��Tianjin 300191��China

Taking a foundation pit in Tianjin as the research subject��the authors established a three dimen- sional coupling model between groundwater flow and land subsidence by the Processing Modflow numerical simula- tion software�� The real time change of the underground water level and land subsidence around the pit was simula- ted when the foundation pit dewatered and drained in case of the construction of supporting and water proof curtain: the value of underground water reduction caused by drainage of foundation pit is about between 0. 90 cm and 82. 15 cm around foundation pit within 80 m area�� Within the 80 m area��the land subsidence is between 0. 001 mm and 26. 21 mm�� The results are in good agreement with the latter monitoring data��which can reflect the influence of the precipitation process to the surrounding environment��