Three-dimensional effects on deformation of deep excavations

Abstract

To research the influence of three-dimensional (3D) effects on the deformation of deep excavations, a database of 30 deep excavations of Nanjing metro stations in China was analysed and comparisons with worldwide cases were conducted. It was found that maximum wall deflections in zones influenced by 3D effects are generally less than those in zones not influenced by 3D effects, while the normalised locations of maximum wall deflections are the same in the two zones. The ratios of maximum wall deflection to excavation depth in zones influenced by 3D effects was found to be generally less than those in zones not influenced by 3D effects. 3D effects were also found to influence ground settlement. Three settlement models – for zones not influenced by 3D effects, zones influenced by 3D effects and zones of soil arch springs – are proposed and comparisons are made. The ratio of maximum ground settlement to excavation depth was found to be 0·12% on average and the ratio of maximum ground settlement to maximum wall deflection was 0·64 on average. The findings of this research can be applied to predict deformation and protect surrounding buildings.