GROUND SUBSIDENCE DUE TO TUNNELING AND EFFECTS ON PILE FOUNDATIONS

Abstract

Tunnels are essential components of infrastructure development projects. But, tunneling in urban areas essentially brings its interaction and hence conflict with existing deep foundations. The stage by stage construction of tunnel below the ground surface causes the settlement of the subsoil and ground surface and also induces axial stresses, moments, settlement etc. on the embedded foundation systems. The amount of settlement and stresses generated again may depend on a number of factors viz. the properties of soil considered, distance of pile foundation system to the tunnel, the tunnel construction phase (tunnel length) etc. The study aims at exploring the characteristics of subsoil profile under the influence of tunneling and feasibility of finite element analysis in studying the effects of variations of soil (sand; as considered here), proximity of tunnel to the pile and the tunnel staged construction. Results showed trends of sagging down subsurface settlement profile affecting the settlement behavior of pile. Also the phase by phase construction of the tunnel also influences the overall soil-pile behavior. Again as the friction angle increases, the deflection of the soil and hence the embedded pile foundations for all the considered cases were found to decrease.