A proposed methodology for analysis of ground settlements caused by tunneling, with particular reference to the “buoyancy” effect

A new analytical method is proposed in order to realistically estimate the ground settlements caused by shallow tunnel construction. In the estimation of these ground settlements with the finite element method (FEM), the weight of the ground which is removed at the tunnel excavation has a large effect on the value of the settlements, when the ground is assumed as an elastic body. Some problems related to the settlements estimated by FEM are pointed out through the elastic theory, a back analysis, and field measurement results. A new analytical method is proposed, which disregards the weight of the ground removed, at the estimation of the excavation forces acting on the tunnel boundary. The appropriateness of the method is confirmed through a comparison between the analytical and the field measurement settlements.