Statistical analysis of characteristics of ground surface settlement caused by deep excavations in Shanghai soft soils

The characteristics of ground surface settlement caused by deep excavations in Shanghai soft soils are studied based on a database of 35 case histories. The magnitude of the maximum ground surface settlement generally increases with the increase of excavation depth. Values of the maximum ground surface settlement generally range from 0.1% H to 0.8% H, with an average value of 0.38% H, where H is the excavation depth. The maximum ground surface settlements increase with the increase of the thickness of soft soils above wall toe, but decrease with the increase of the factor of safety against basal heave. The maximum ground surface settlement is independent of the system stiffness of the retaining system and the embedded depth ratio of retaining wall. The lower and upper bound values of the ratio between the maximum ground surface settlement and the maximum lateral displacement of wall are 0.4 and 2.0, respectively, with an average value of 0.84. Distribution of the ground settlement is analyzed. The upper bounds of the ground settlement profiles are proposed for the case histories in Shanghai. The maximum ground surface distortion ranges from 0.001 to 0.017. Relationship between the maximum ground surface distortion and the maximum ground surface settlement is also established.