Study On Instability And Water Inrush Mechanism Of Surrounding Rock Caused By Blasting Excavation Of Deep Buried High-risk Karst Tunnel

At present,the design and construction of deep buried karst tunnels is a worldwide problem that plagues domestic and foreign experts.The risk of water inrush should be considered during the process of design and blasting excavation of the deep karst tunnels.Especially during blasting excavation: blasting excavation caused damage to the surrounding rock;Damaged rocks increase the risk of water inrush from karst tunnels.The G577 road is 11.7km long,from Jinghe to Yining County.The tunnel crosses the Boroconu Mountain in the northern Tianshan Mountains.The geological structure is complex.The faults and folds are very developed,and the hydrological conditions are very developed.The thesis focusing on the study of seepage-stress-damage coupling of surrounding rock during blasting excavation of deep karst tunnel in the northern Tianshan Mountains,reveals the propagation law of effective stress of surrounding rock and the damage mechanism of surrounding rock during blasting excavation of deep buried karst tunnel,by using of theoretical analysis,field test and numerical analysis.The thesis studys The variation law of seepage field of surrounding rock under different geostress,different karst water pressure,spatial position and size of different karst caves and revises the traditional calculation method of tunnel water inflow,and proposes a new method for calculating the water inflow of tunnel under the condition of seepage field.Mainly completed the following aspects of work:(1)Studying the hydrogeological conditions and karst space development characteristics of deep karst formation by analysising the engineering case.Studying on the distribution of the structural fracture of surrounding rock between tunnel and cave and the buried depth of tunnel in karst hydrodynamic section on tunnel karst water.Studying the development characteristics of karst in the northern Tianshan Mountains of Xinjiang by means of surface karst investigation.Analyzing the development and characteristics of karst in the northern Tianshan Mountains of Xinjiang and the geological factors of water inrush.(2)Based on the elastoplastic damage constitutive model of rock mass,analyzing the method of solving the damage variable of the water-bearing fractured rock mass under the action of dynamic and static combination(blasting load and ground stress).The coefficient evolution equation of damaged rock is used to establish the seepage-stress-damage coupling model under the combined action of rock and body dynamic and static combination(with blasting load and ground stress).The coupling model is embedded into COMSOL Multiphysics software through secondary development of finite element software.Carrying out the numerical simulation of the excavation process of the Jingyihu railway tunnel in the DK110+500 section by using this model,and comparing with the field measured data.Through data comparison,simulating the feasibility of the coupled model of seepage-stress-damage coupling under the dynamic and static combination of rock mass.(3)Using numerical simulation method to analyze the effective stress variation law and damage range of surrounding rock during blasting excavation of deep karst tunnel under different geostress,different karst water pressure,different karst space locations and different karst cave sizes.The coupling effect of rock damage cracking and seepage field under the action of high internal water pressure in the cave.Under the influence of different factors,the manifestation of seepage field changes is to change the pore water pressure in the surrounding rock,which in turn changes the propagation law of effective stress in surrounding rock and the damage range of surrounding rock.(4)Based on the variation law of seepage field of surrounding rock and the calculation method of tunnel water inflow,correcting the traditional calculation method of water inflow prediction.Analyzing the amount of water inflow in the tunnel by studying the variation law of permeability coefficient of surrounding rock under different geostresses,different cave water pressures,spatial positions and sizes of different caves.Establishing calculation model for water inflow in tunnels under conditions of variation of permeability coefficient of surrounding rock,and comparing The numerical model with the in-situ test in the field.