Evaluation of Surface Displacement Equation due to Tunneling in Cohesionless Soil

Abstract

Construction of tunnels in soft ground induces soil movement, which could seriously affect the stability of existing structures. Evaluation of the effect of tunnel construction on the soil movement requires the solution of a complex soil–structure interaction problem. Finite element method (FEM) is considered as a good numerical tool to model tunnel systemperformance. The soil stresses and the soil displacements around a tunnel system are affected by the tunnel construction. The influence zone depends on subsoil properties, tunnel depth, tunnel size, and tunnel support system. In the present study, finite elements analysis (FEA) is used to model soil-tunnel system performance based on a case study to investigate surface displacement due to tunneling. The Greater Cairo metro tunnel (Line 3) is considered in the present study as case study. The surface displacements obtained by surface displacement equation (SDE) proposed by Peck(1969) and Schmidt (1969) are presented and discussed. The main objective of this study is to examine surface displacements obtained by the FEA with those obtained by the SDE based on different sand soil types. However, the SDE does not consider the impact of different sand soil types on the surface settlement due to tunneling. The study focuses on the parameters used in the SDE based on different sand soil densities. The limitation of the parameters used in the SDE is discussed and established to predict the surface displacement due to tunneling at different sand soil densities.