Zonal disintegration test of deep tunnel under plane strain conditions

To investigate the zonal disintegration form of the surrounding rock in deep tunnels, model tests were performed in the simulation set-up of fracture mechanism and support technology of surrounding rock in deep tunnel. The test results illustrate that the first fracture of the surrounding rock occurred at the intersection of the tunnel floor and the side wall. After more serious destruction, the side wall and the vault were destroyed. Although the fracture width of each surrounding rock mass was distinct, they were relatively uniform with a nearly continuous fracture form. The width of the split bodies of the model tunnels (i.e., the annular zonal disintegration area) developed with an increasing load. It was observed from the fitting curves of the data that all radial strain values of the surrounding rock were more symmetric with a smooth fitting curve, and the maximum value occurred near the tunnel wall before reducing instantly. The circumferential strain values were dispersed and the data were inconsistent with the fitting curve, which caused some data to be unreliable. The phenomenon of zonal disintegration was primarily caused by radial tension strain of the surrounding rock. This phenomenon would not extend indefinitely as the rupture range would be limited to a certain extent, because the maximum radial tension strain of the surrounding rock was less than the limiting value.