Seismic stability of a long unlined circular tunnel in sloping ground

Abstract

The stability of an unlined long circular tunnel underneath an infinite slope is examined with the inclusion of seismic body forces. The study is carried out by using the lower bound finite element limit analysis. The values of γH/c are plotted as a function of H/D, [Formula: see text], β, and kh in the form of charts. The magnitude of γH/c is found to decrease consistently with an increase in β and kh. With an increase in the magnitude of β and kh, the plastic zone around the periphery of the tunnel becomes more and more asymmetric. The stability charts presented in this note would be useful for examining the effect of slope angle on the stability of an unsupported circular tunnel under seismic forces.