The application of active support technology of prestressed anchor rod in tunnel engineering is increasing;however,its applicability and mechanism of action for shallow-buried large-span rock tunnels are not yet clear.Taking the underground excavation station project in Qingdao Metro as the background,the contrastive investigation,numerical calculation and model experiment were carried out,and the comparative analysis of the supporting effect of prestressed bolt and non-prestressed bolt on massive surrounding rock was conducted.The active support mechanism and theoretical model of shallow-buried large-span rock tunnel were studied from three aspects,namely,rock stress compensation,arching compression of blocky rock mass,and dangerous block controlling.Then the on-site application was further carried out.The results show that the original scheme for the support mainly followed the concepts of soil tunnel support,and the understanding and utilization of the self-supporting capacity of the surrounding rock was insufficient.The tensile stress zone of the surrounding rock disappeared and the plastic zone was significantly reduced,the normal compressive contact stress increased about 0.2-0.3 MPa on the rock joints.The sliding displacement at the joints of the key block was effectively controlled,and the overall stability of the tunnel surrounding rock was effectively improved when the rock bolt worked with prestress(100 kN).The established theoretical model for active support of rock tunnels internalized the stress compensation object from the excavation surface to the rock mass structural plane;and the support material consumption of the optimized support schemes was reduced by about 30％,the construction period was shortened by 17％and the tunnel settlement was reduced by about 50％compared with the original scheme.
关键词
预应力锚杆/主动支护/地铁暗挖车站/硬岩/大跨隧道
Key words
Prestressed rock bolt/Active support/Underground excavated subway station/Hard rock/Large-span tunnel
维普
万方数据