APPLICATION OF BACK ANALYSIS TO A TUNNEL WITH TWO-STEP BENCH

SYNOPSIS Direct back analysis program [1] was applied to a tunnel with two-step bench, and the validity of its application was investigated. Three representative sections were chosen, and back analysis was carried out at the ends of both the upper and the lower bench excavations. Based on the results of the back analysis of the upper bench excavation, conventional Finite Element Analysis was performed to predict the tunnel behavior after the lower bench excavation for the third section. To the first and the second sections elastic and homogeneous back analysis was applicable. On the other hand, nonhomogeneous back analysis was appropriate for the third section.