Study On System Rockbolts Supporting Effect For Expressway Tunnel In Weak Surrounding Rock

The rockbolts supporting technique has been applied to every field of geotechnical engineering because of its unique function, and achieved good effect. Especially in the tunnel engineering, the application of the rockbolt supporting technique is more widely. In the process of tunnel construction, people often encounter a variety of weak surround rock, and use system rockbolts in weak surround rock. Domestic and foreign engineering technicians and cholars carried out a large number of test and research on the efficacy of the system rockbolts in the weak surrounding rock. At present, there are two views: some people think that should cancel system rockbolts, but another people think that should be retained. So, the controversy remains to continue about this question.This paper is on the background of Zhangzhuo expressway Duya Tunnel engineering. At first, based on the investigation, this research obtained the real data of the broken pebble ground, and its physical mechanical parameters are obtained by experiment. Then this research used the ABAQUS software for 3D numerical simulation and built two models, one had system rockbolts and another one had no system rockbolts. Deformation of surrounding rock, surrounding rock stress and primary supporting stress were comparatively analyzed in the simulation of tunnel construction. The results showed that deformation and stress was not obvious between two models, and distribution of cloud image also had no obvious difference. It was concluded that effect of system rockbolts was not obvious in weak surround rock.In order to study the stress of the surrounding rock and supporting structure in tunnel construction, deformation of surrounding rock, monitor of the surrounding rock stress and primary supporting stress were carried out in the process of tunnel construction. The analysis of monitoring data about the deformation of surrounding rock, the surrounding rock stress and the supporting structure stress further showed that supporting effect of system rockbolts was not obvious in Duya tunnel, so the system rockbolts should be abandoned in this engineering.