Failure process and characteristics of deep concrete-supported arch tunnel under true-triaxial stress

Abstract

In deep underground rock engineering, tunnel structures after concrete support are often subjected to failure because of stress variation. In this study, to understand the failure process and characteristics of deep concrete-supported tunnel, true-triaxial compression tests were conducted on concrete-supported and unsupported tunnel model specimens using a true-triaxial test system. An AE system and a microcamera were used to capture the AE events and failure evolution process of the hole sidewalls in rock specimens, respectively. The test results show that after concrete support, the failure characteristics of the hole sidewalls are converted from dynamic rockburst failure to static spalling failure, and the initial vertical failure stress of the hole sidewalls is significantly increased. The failure of the hole sidewalls in the concrete-supported tunnel model specimen experiences the calm stage, the cracking and buckling of concrete-support layer stage, the spalling of concrete-support layer stage, and the spalling of concrete-support layer and rock layer stage. The cumulative AE counts of the concrete-supported tunnel model specimen are less than those of the unsupported one at any same time during loading. Comparing the failure processes and characteristics of hole sidewalls in the two types of specimens, the curbing effect of concrete support on the failure of tunnel is confirmed. The results of this study contribute to the understanding of the failure behavior of deep rock tunnels with concrete support.