Computation method for long-term surface and subsurface settlements induced by excavation of tunnels in clays

Based on the Mair's theory of immediate settlement of soil due to tunneling, and the results of finite element simulation, a computation method for the long-term settlement of the soil at surface and subsurface is proposed. Ong’s centrifuge test is simulated first to verify the validity of the finite element model, then a numerical study on the long-term settlement of the soil at different depths is carried out. The relationship between ground losses under immediate and long-term conditions is established. Formulas for width parameter and the maximum settlement of settlement trough at different depths are also given, and the profile of settlement trough can be determined. Compared with the field measurement and numerical simulation, the validity of the proposed method is demonstrated. It can be employed in practical projects.