Survey and cause analyses of ground surface deformation near a foundation pit slope: a case study in the Three Gorges area, China

It is common that the deformation of an excavation slope leads to the displacement or even destruction of the surrounding buildings. An effective way to put an end to such accidents is to have adequate knowledge on the trigger factors of the deformation and failure of excavation slopes. Herein, taking the foundation pit slope at the Cultural Square in Badong County, China as an example, we carried out a site survey, including the engineering geology condition, the terrain change process, the spatial distribution characteristics of the surface crack and the construction process of the foundation pit. A further study was performed on the trigger factors, such as geological environment, earthquake, rainfall, fluctuation of reservoir level, human engineering activities, on ground surface deformation. The results show that the complex engineering geological condition and weak geological environment are the internal factors that lead to the deformation of the foundation pit slop. Earthquakes and fluctuations of reservoir level have little effect on this deformation, while rainfall and the excavation have a significant influence on it. The excavation process destroys the original geological environment and is thus the critical external factor inducing the formation and growth of crack, and rainfall intensifies the deformation.