Numerical and Analytical Investigation of Ground Surface Settlement Due to Subway Excavation

Abstract

In the congested urban areas, tunnelling close to existing structures often occurs due to the lack of space. Consequently, tunnelling-induced ground movements may cause serious damage to the adjacent structures. Ground surface settlement caused by tunnel excavation varies in magnitude and trend depending on several factors such as tunnel geometry, ground conditions, etc. There are several emp irical, semi-emp irical equations and numerical methods available to estimateground surface settlement associated with excavation activit ies, however among these methods most of empirical and semi-emp irical based methods do not simu ltaneously take all the relevant factors in the co mplex condition into account. In comp lex conditions, numerical methods can be used for resulting accurate predictions. In this paper, ground movement in a highly populated region of Iran's capital city, Tehran, induced by excavation and construction of 7 th line of Tehran subway has been investigated. It was aimed to analyse the ground displacements and surface settlement which hasbeen induced by tunnelling using Earth Pressure Balance-Shield Tunnel Boring Machine. The analysis was performed by Finite difference Method (FDM) using FLA C 3D FDM package. Results from performed nu merical analysis show good agreement with obtained results fro m analytical and empirical methods. In addition, effect o f some impo rtant factors such as tunnel geometry and ground properties on ground surface settlement has been investigated. Obtained results indicate that ground surface settlement is more sensitive to tunnel geometry rather than height of tunnel placement.