Analysis of the mechanism and failure mode of landslides subjected to transient seepage in a Piedmont region of Nanjing area

The landslide mechanism and failure mode of the gently sloping Piedmont region are analyzed in Fangshan and Zhutoushan hills in the Nanjing area of Jiangsu Province, China. These hills are underlain by volcanic rocks and have a distinctive stratigraphic structure composed of fill or clay at the surface, coarse-grained soil or fully weathered rock in the middle, and highly or moderately weathered rock at the bottom. Landslides occurred during or after heavy rainfall, and the monitored displacements of the slope surface indicated that sliding had not stopped after a long period of continuous rainfall. Through monitoring of groundwater and simulation, we found that the low-permeability highly weathered rock can restrict the activity of the lower aquifer, resulting in a rapid rise of pore pressure and formation of confined water in response to rainfall, which can lead to slope failure. We discuss the mechanism and avulsed–drifted failure mode of the landslides considering seepage deformation and pressure balance. Finally, we propose appropriate control measures for these landslides. The results of this paper will contribute to prevention of similar landslide geological hazards.