STUDY ON BACKFILL SCHEMES COMPARISON OF A SURFACE CAVITY CAUSED BY TUNNEL COLLAPSE IN LOESS DISTRICT

A tunnel in loess district collapsed due to heavy rain, resulting in a cylindrical cavity on surface. Two schemes, reinforce-and-cover and cut-and-cover, have been brought forward for backfill, and compared in tunnel structure moment and construction cost to decide which one should be adopted. Tunnel structure moment can be calculated by ANSYS, using load-structure method and strata-structure method, respectively. It comes to conclusion that tunnel structure would be safer and construction more economical if employed the first scheme to refill the cavity.