Analytical prediction for tunneling-induced ground movements in clays

Current design practice to predict tunneling-induced ground movements is generally based on empirical methods that are subjected to some important limitations. For a ground deformation prediction due to tunneling to be accurate, the prediction methods should account for the effect of a number of parameters, such as tunnel construction method and tunnel-driving details, tunnel depth and diameter, initial stress state, and stress-strain behavior of the soil around tunnel. In this paper, the traditional definition of the ground loss parameter is redefined as "equivalent ground loss epsilon parameter" with respect to gap "g'' parameters and incorporated on to analytical solutions to predict the ground movements around the tunnel in clays. The applicability of these proposed analytical solutions is then checked with five case records, which encompass a range of ground conditions from very stiff to soft clays. Equivalent ground loss parameters predicted on the basis of the new approach are in good agreement with reported empirical ground loss parameters, especially for tunnels in stiff clay. The proposed new approach tends to overpredict the ground loss parameter for tunnels in soft clay, and the predicted surface settlement troughs are slightly wider than the field observations. Nevertheless, in general, the observed and predicted settlement and horizontal movements are in good agreement for tunnels in uniform clay.