ABSTRACT
It is common that the void is formed behind the tunnel lining on the crown portion of the aged tunnel due to the geological reasons. It is strongly recommended that those void is filled with the grouting material to improve the stability of the tunnel. Authors newly developed the grouting method called “Aqua Grout Method”using the new grouting material consisting of cement, bentonite, super absorbent polymer, set accelerating agent and water. Through its applications into the actual aged tunnels, the Aqua grout method with new material is found to be very effective as the back-fill method for the voids behind the lining of the aged tunnel.
