Abstract: The safety hazards induced by the artesian groundwater beneath the soil strata is one of the factors that posting safety hazards in the deep excavations. The case history of a piping accident occurred in a deep excavation project in Jiangbei New District in Nanjing City is presented in this paper. The vertical and horizontal limits of the piping disturbed zone were evaluated through the Cone Penetration Test (CPT). The CPT test result comparisons before and after the accident can have the following conclusions: the mechanical properties of the ④_2a silty fine sand lens with silty soil around the piping points are close to that of worst soil area outside the excavated area. The CPT results are consistent with the failed conditions; It is feasible to use the CPT test to analyze the stratigraphic disturbance zone after the piping; which provides some reference for the remediation of the excavation piping hazards induced by the artesian groundwater below the excavation zone.

Key words: Deep Excavation, Piping, Cone Penetration Test, Strata Disturbance