Centrifuge Study of Faulting Effects on Tunnel

Abstract

If a tunnel crosses a geological fault which is considered to be active, the possibility of a displacement in the fault must be accounted for in the tunnel design. When the tunnel is embedded in soil, the assessment of the effect of the fault movement is not easy to assess. As a guide to analysis, a series of correctly scaled model experiments in a centrifuge is undertaken. The deflections and stresses induced in a tunnel crossing a fault caused by: (a) Fault displacement; and (b) differential earthquake motions across the fault are quantified by a series of centrifuge tests on a finite length model tunnel. The centrifuge results are used to calibrate a one‐dimensional finite element model of the tunnel for soil‐tunnel interaction effects. The numerical model is then used to predict the response of an essentially infinite length tunnel for design purposes. Bending movements, displacements and shears are displayed. Surprisingly small changes in the bending movements from the finite‐length to the infinite tunnel case are obtained.