| With the rapid development of water conservancy and high-speed railways in China,more and more deep and long tunnels are being built.And owing to the deep burial depth and high ground stress,the geological disasters,such as rockburst,during the construction procedure are more and more serious.Based on the previous research on rock burst,and combined with field survey,site investigation,and site rockburst statistics from Qinling diversion tunnel,the rockburst mechanism is studied in this paper.The occurrence law of rock bursts in the tunnel diversion of the Qinling Mountains is summarized by the statistical analysis of site records of rock burst in addition,electron microscope scans on rock fracture and micro-damage mechanism of rockburst were analyzed.Further more,the rockburst phenomenon under different buried depths was simulated by the discrete element software UDEC to investigate the mechanism of rockburst for different buried depths,and the rockburst mechanism in the Qinling tunnel was exposited.The main conclusions are as follows:(1)On the basis of field surveys and statistical analysis of on-site rockburst records,through analysis of rockbursts in intensity scales,formations,lithology,surrounding rock joints and fractures,groundwater,hole axis,tunnel cross-section,ground stress,depth of burial,As well as the distribution and development of space,the law of occurrence of rockburst in the excavation section of the Qinling Diversion Tunnel has been obtained.(2)Through electron microscopy scanning and microscopic analysis of rockbursts in the tunnel section of the typical rockburst in the Qinling Diversion tunnel,it can be concluded that the rockburst rock fracture patterns are tensile fracture pattern and shear fracture pattern.(3)Through the micro-fracturing analysis of rock burst,it can be seen that the micro-fracture mechanism of the rock burst rock in the Qinling diversion tunnel is: tensile fracture,micro fracture mode is cleavage and intergranular fracture,shear fracture is along the crystal plane fracture,cut Crystal fractures and scrubber shear failures and their complex coupled fracture modes.(4)Through the analysis of rock mechanics mechanism of rock burst,the micro-damage mechanism of rock burst rock in the Qinling diversion tunnel is mainly tensile failure,tensile shear coexistence damage,and local shear failure.And the microscopic mechanism of rockburst with different intensity levels is different.(5)According to the fracture micro-morphology and micro-damage mechanism,the micro-mechanism of the rock burst in the Qinling diversion tunnel is obtained.Under the effect of the secondary stress re-adjustment and distribution,various micro-cracks or micro-holes in the tunnel surrounding rock itself are also Under the action of tensile stress or shear stress,micro-fractures occur between grains or crystals,and they expand,intersect,and penetrate.Eventually they evolve into macroscopic cracking and rockburst.(6)Through discrete element UDEC software,the rockburst failure process in different buried depths is numerically simulated and analyzed.Through displacement,velocity tracking of broken rock,plastic failure zone distribution,maximum principal stress analysis,and joint failure status,different depths are obtained.Rock burst mechanism.With the increase of burial depth,the more energy accumulated in the rock body,the more frequent the rock burst,the secondary stress distribution and stress concentration position are different,and the secondary stress value increases with the burying depth.(7)According to the microscopic mechanism analysis and UDEC numerical simulation of the Qinling diversion tunnel,the process of rockburst is a process of energy accumulation—crack formation—energy release.The specific stage is energy accumulation—the formation of a burst body—the rupture surface penetrates—formation rock Explosion phenomenon — Stabilize these five phases. |
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