Abstract
A prototype loading test apparatus that can imitate situations of a concrete lining of an irrigation tunnel with a hollow behind it was fabricated to investigate the mechanism of cracking commonly observed on spring lines in sidewalls of irrigation tunnels. In addition, effectiveness of a backfill grouting method to prevent further cracking and deformation in concrete lining was examined. In the cases with a hollow behind the arch, test specimens of scaled concrete lining showed outward displacement on their crowns due to the lack of vertical load, as well as inward displacement in side walls by horizontal load. This deformation in side walls led cracking on the spring lines, as in the cases of real irrigation tunnels. It is confirmed that a hollow behind the arch remarkably reduces the load bearing capacity of concrete lining. It becomes smaller with a larger hollow, reducing the difference between the cracking and ultimate loads of the lining. The results of experiments simulating a backfill grouting hollows behind the linings showed a strong possibility to reduce abnormal deformation of linings, as well as to increase cracking and ultimate loads greatly.
