Abstract:During the construction of foundation pit,some characteristic factors about groundwater seepage field,should be investigated for the dewatering,antiseepage and supporting works. Temperature is a natural tracer of groundwater movement. Normal temperature distribution of strata is continuous and regular. Under the influence point of seasonal temperature,strata temperature will increase with depth,but groundwater movement will bring abnormality to this distribution. This abnormality of temperature curve can be used to study the permeability of strata and locate the concentrated leakage passage. Related information about groundwater seepage field is provided by the abnormality of the curve of temperature vs. depth,such as the location of strong leakage layer and the relation of groundwater recharge. As an example,ground water temperature tracer detection is performed in the foundation pit of Sanshanjie Subway Station in Nanjing. The case study shows that the major reason of leakage of foundation pit is the inadequate depth of underground continuous wall and the existence of faults on the wall. Deep confined water is drained out and then this will cause the ground settlement around the foundation pit. Corresponding countermeases are proposed accordingly.