Equation for Maximum Ground Surface Settlement due to Bored Tunnelling in Cohesive and Cohesionless Soils Obtained by Numerical Simulations

Abstract

Estimation of tunnelling-induced surface settlements requires empirical, analytical, or finite element analysis methods to be applied. Tunnelling method and construction sequence highly influence the surface settlements and require appropriate consideration in the analyses. In this research, the effect of single tunnel construction in soft clays, stiff clays, loose sand, and dense sand was simulated using Plaxis 2D finite element software. The results were interpreted to obtain maximum settlement at the ground surface. The effect of varying tunnelling depth, diameter, and volume loss on the maximum ground surface settlement and the location of inflection point along the ground surface settlement curve was investigated. Based on the results obtained, a set of equations for maximum surface settlement and inflection point were developed that provides a method of evaluation for maximum surface settlement and inflection point variation with respect to the tunnel diameter, depth, and volume loss. The multivariable prediction equation for maximum surface settlement is validated to be very successful overall for tunnelling in most soils, and the analyses were calibrated using field data from various tunnelling projects presented in the literature.