| The geological structure of karst area is special,the development of karst is complex,and the distribution of karst caves has the characteristics of many,staggered and overlapping.Tunnels built in these areas tend to be deeper and have higher in-situ stress in the surrounding rock.The development of karst in deep strata makes the integrity and strength of rock strata around the tunnel poor,and the water pressure in rock fractures is also high.Tunnel is often inevitably close to the karst cave,or even through the karst cave,facing a very high construction risk,water and mud inrush accidents occur frequently,has become one of the most serious disasters in the construction of karst tunnel.In this paper,the failure mechanism and the safety thickness of the outburst prevention structure between tunnel and karst cave are studied by means of the discrete-continuous coupling model.The main research work and results are as follows:(1)The numerical model of triaxial compression is established by using discrete element software,and the influence characteristics of macro and micro parameters of simulated rock mass materials are studied.The influence law of the meso-parameters of the parallel bonding model on the macro-parameters of the simulated rock mass is obtained,and the sensitivity and significance are analyzed.The research results can provide a reference for the rapid matching of the macro-meso-parameters of the parallel bonding model.(2)According to the influence characteristics of macro-meso-parameters of the parallel bonding model,the surrounding rock parameters of the supported engineering site are calibrated quickly,and the discrete-continuous coupling model and continuous model are established for comparative analysis.The matching results are verified from the perspective of displacement field and stress field,which verified the accuracy of the calculation of the coupling model.(3)A discrete and continuous coupling model is established to simulate the failure process of waterproof-Resistant slab.From the perspective of the evolution process of waterproof-Resistant slab,three types of failure modes of waterproof-Resistant slab are summarized: bending failure mode,integral shear failure mode and composite failure mode.(4)By using discrete continuous coupling method to establish numerical model and orthogonal test,the variation rule of the minimum safe thickness of the waterproof-Resistant slab under the influence of various influencing factors is summarized when the karst cave is located on the upper,right and lower sides of the tunnel.The prediction model of the minimum safe thickness of the waterproof-Resistant slab at different positions is obtained by multivariate fitting of the simulation results. |
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