Compared with shallow buried tunnel,the high stress caused by the increase of buried depth makes the safety evaluation of deep buried tunnel more complicated.Therefore,this paper designs and optimizes the bolt support mode of deep buried tunnel under impact load with the premise of in-situ stress balance by combining the finite and infinite elements.This paper not only studies the deformation characteristics of surrounding rock under impact load,but also analyzes the influence of length,density,length interval arrangement and key support of arch foot on the safety of tunnel.The results show that the Mises stress has almost no change before and after the in-situ stress balance,but the displacement is highly affected.When impact wave is loaded,the Mises stress first increases slightly with the increase of bolt length and density.When the length and density of the bolt increase to a certain value,the Mises stress no longer increases.The displacement and plastic strain of the cavern wall reach their minimum.In this case,the surrounding rock of the tunnel reaches a relatively safe state.Regarding to the bolt spacing,reasonable arrangement of short dense bolts is beneficial to the safety of tunnel,and the increase of the number of long anchors can improve the safety of the tunnel.This is due to the wide reinforcement range of long anchor to the surrounding rock.A high strength bearing layer is formed above the tunnel.It can withstand a large load,and transfer the load to the bottom of the straight wall.When the arch foot of the cavern is mainly supported,the displacement of the arch foot as well as the whole wall is reduced.
deep tunnelin situ stress balancebolt supportstress of surrounding rock
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