Abstract: The integrity of the foundation pit enclosure structure is key to ensure the safe excavation of the foundation pit. In this study, the pumpingtracing method is proposed for detecting underground diaphragm wall leakage, and a case study is conducted on a foundation pit project of Hudian road station on Suzhou railway line 8 to validate its applicability in practical projects. First, a joint leakage detection method of pumping and tracing is applied by placing boreholes on both sides of the underground diaphragm wall. Second, the location of the hidden leakages in the underground diaphragm wall is investigated according to the test data under natural and pumping conditions. Finally, a twodimensional finite element numerical model is established to simulate the observation well flow rate under different seepage depths, and the results are compared with the actual measured results. The study results demonstrate the feasibility and effectiveness of the proposed method in underground diaphragm wall leakage detection.

Key words: underground diaphragm wall, leakage detection, pumpingtracing method, finite element simulation