A New Method based on Centrifuge Model Test for Evaluating Ground Settlement Induced by Tunneling

Current methods for evaluating the ground settlement due to tunneling in loess do not fully consider the special engineering properties of loess. This paper first studied the ground settlement due to tunnel construction in loess by conducting a uniquely designed centrifuge model test. Then the ground settlements were calculated using a currently widely used method and compared with the measured values from the centrifuge model test. The results indicated a substantial difference between the calculated and measured settlement profiles. For the stratum at shallow depth, the calculated settlement profiles were flatter with smaller maximum settlement S_max at the tunnel centerline and larger settlement far from the centerline than those from the centrifuge model test; while for the stratum near the tunnel crown, the opposite was obtained. The main reason for the difference is because of the large void structure and high compressibility of loess which causes additional settlement at shallow depth. Based on the centrifuge model test results, a new method which properly considers the special engineering characteristics of loess was proposed to evaluate the settlement due to tunnel construction in loess. The calculated settlement profiles using the new method were in good agreement with those from the centrifuge model test. Finally, the new method was used to evaluate the ground settlement caused by the construction of a Metro tunnel in loess and satisfactory results were obtained.