Research On The Composite Supporting Effect Of Bolt-Shotcrete And Reinforced Ribs Of Sprayed Concrete

Norwegian Method of Tunneling suggests that the use of bolt-shotcrete and reinforced ribs of sprayed concrete(which consists of steel fibre shotcrete?rock bolt?reinforced ribs of sprayed concrete)as a permanent support obtains remarkable engineering and economic effects.In recent years,many research teams took on studies into the structural style?construction technology?supporting effect of the reinforced ribs of sprayed concrete.The studies show that the structure is a kind of effective support type of underground engineering.However,there are limited researches on bolt-shotcrete and reinforced ribs of sprayed concrete's supporting technology,which affects the spread and application of this technology in our country.For better application of the bolt-shotcrete and reinforced ribs of sprayed concrete's support,this thesis used the finite difference software FLAC3D to conduct further study into the problems involved in the interaction of the surrounding rock and support structure,basing on a weak surrounding rock section(Q=0.01)of a underground traffic tunnel.The main research content is as follows:(1)The reinforcement mechanism of the bolt-shotcrete and reinforced ribs of sprayed concrete's composite support was stated,the interaction between surrounding rock and support structure and the construction technology of the composite support introduced.(2)The finite difference software FLAC3D was used to simulate the tunnel excavation and supporting process.The supporting effects when without support or with different types of support were analyzed from the aspects of steel fibre shotcrete?steel fibre shotcrete and rock bolt?bolt-shotcrete and reinforced ribs of sprayed concrete.The results indicated that the consolidation effect of the surrounding rocks significant improved,when using bolt-shotcrete and reinforced ribs of sprayed concrete.(3)The finite difference software FLAC3D was used to simulate the supporting process of a tunnel.The influence of different support parameters on the consolidation of the bolt--shotcrete and reinforced ribs of sprayed concrete's composite support was studied from the aspects of rock bolt's length?reinforced ribs of sprayed concrete's thickness and spacing.The results indicated that the best supporting effect of the composite support structure was achieved when the rock bolt's length was 3-4m,the reinforced ribs of sprayed concrete's thickness was 0.5-0.6m and the reinforced ribs of sprayed concrete's spacing was 2-3m.The research results of the paper can provide a beneficial reference for the design and construction of the similar composite support structure in the underground engineering.