Effect of the overconsolidation ratio of soils in surface settlements due to tunneling

Construction of urban tunnels requires the control of surface subsidence to minimize any disturbance to nearby buildings and services. Past study of surface subsidence has been limited to mainly empirical solutions based on field studies, and very few analytical studies have been carried out. The available analytical solutions are not sufficient to include complex ground conditions; hence, a comprehensive analytical solution coupled with numerical modeling is necessary to model the effect of surface subsidence due to tunneling. This paper presents the results of modeling of surface settlements due to tunneling using the finite element method. The effect of the overconsolidation ratio of soils expressed in terms of the coefficient of earth pressure at rest (K₀) on surface subsidence due to tunneling is investigated. It is demonstrated that surface settlements appear to be sensitive to K₀ values, and for geotechnical calculations pertaining to overconsolidated sand and clay soil, K₀ values of 0.6 and 0.8, respectively, are proposed.