Study On Performance Of Shotcrete Under Heat Harm Tunnel And Structure Behavior Analysis

With the rapid development of China railway and the progress of tunnel construction technology,tunnel construction gradually develop to the direction of long and deep buried, meanwhile,high temperature geothermal problem is encountered, but the present research mainly confined to through the external measures or temporary measures to improve the thermal damage problem But did not do research of mechanism inquiry and long-term high temperature material thermal damage performance. Based on the national natural science fund project (51008253) and DaRui railway gaoligong mountains tunnel project, this paper studied the heat harm performance of shotcrete direct bonding with rocks through the experimental study and numerical simulation.The main research work and results were as follows:(1) The effect of heat harm on bond strength of shotcrete with rock is studied.The eaperi-ment study on shotcrete bond strength with rock for two kinds of strength grade (C25and C30) was carried out by selection of rock slab, simulating heat harm environment design,wet shotcr-ete technology,bond strength determination method (splitting method and pull method) and mi-croscopic test.Test results show that, hot air environment and hot humid environment both refl-ected the the pour shrinkage phenomenon of bonding strength caused by thermal damage, the drying shrinkage of bond strength of shotcrete and rock in hot air environment relative to the drying shrinkage in hot humid environment is more obvious, and the drying shrinkage intensif-ies with the temperature, especially70℃condition more significant.(2) The effect of heat harm on deformation performance of shotcrete is studied. The expe-riment was measured by contact method,the deformation performance of shotcrete on the heat harm condition and70℃-dry conditions with different dosage of fly ash,slag powder,1.0%steel fiber,0.1%polypropylene fiber and hybrid fiber is researched. The test results show that,theshotcrete in hot and humid environment is intumescent, drying shrinkage in the enviro-nment of hot air is more serious, while jet concrete shrinkage can be prevented with the join of steel fiber.(3) The improve study of bond strength of shotcrete with rock under heat harm environm-ent is carried on. The experiment research is mainly on the content of bond strength of shotcr-rete mixing slag,fly ash,1%steel fiber,0.1%polypropylene fiber and double doped fiber under70℃-dry and wet two kinds working condition,and compared with datum shotcrete for anal-ysis.Test results show that, when the shotcrete mix fly ash alone in hot and humid environment, the bond strength of shotcrete and rock is significantly improved, single steel fiber is mixed can improve the bonding strength of shotcrete and rock in the dry environment.(4) Numerical simulation adopt ANSYS method and based on V surrounding rock of tunnel in Gaoligong mountain as the backing, and the temperature distribution and the stress of the tunnel under the coupled action of surrounding rock stress and geothermal were analyzed. The analysis results show that, the thermal insulating layer in tunnel have significantly reduced effect on temperature of secondary lining concrete, and insulation coefficient is smaller, the reduction of temperature is more obvious; the temperature stress distribution of the tunnel having thermal insulating layer is more uniform than the tunnel having no insulating layer.