Abstract With the increase of excavation depth,the zonal disintegration phenomenon in surrounding rock of deep cavern appears,which is quite different from the failure mode of shallow cavity. In order to further study the mechanism of zonal disintegration,an elastic damage softening model for zonal disintegration was put forward based on the strain gradient theory and continuum damage mechanics. The equilibrium equations and boundary conditions of quasi-plane strain problem were deduced considering the out-of-plane stress influence. The numerical solutions of radial displacement and radial strain and stresses in deep surrounding rockmass were calculated using Matlab. The numerical solutions presented an oscillation mode. The theoretical calculated values are in good agreement with the model test data. The applicability of elastic damage softening model for zonal disintegration in the explanation of zonal disintegration was confirmed. The oscillation mode of stress in deep surrounding rock is the critical reason for the formation of zonal disintegration.
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