Aiming at the large deformation instability problem caused by the excavation unloading of a coal roadway in deep-buried slowly inclined jointed rock mass, the geomechanical parameters and deformation failure characteristics of an engineering geomechanical model were investigated. The in-situ stress state of the model was measured with the stress relief method. The geological and mechanical properties of roadway surrounding rock were described. The surrounding rock structure was revealed with the electron microscopy scanning method, micro-fractures and randomly distributed joints highly developed in roadway surrounding rock. Field investigation and monitoring indicated the cross-section of roadway surrounding rock shrank continuously and the deformation distribution was obviously asymmetric. Shotcrete spalling and cable broken failures frequently occurred in the middle and ride side of roof and right rib. Based on the geomechanical conditions of the coal roadway, a discrete element numerical model of coal roadway in gently inclined jointed rock mass was established. The parameters of rock mass in the numerical model were calibrated. The model ran in unsupported condition to restore the evolution process of stress, crack propagation and deformation in roadway surrounding rock due to gradual deviatoric stress release caused by excavation. On this basis, the space-time evolution characteristics and law of stress, crack propagation and deformation were obtained and then the asymmetric large fragmentation and dilatation deformation failure mechanism of roadway surrounding rock in deep-buried slowly inclined jointed rock mass was revealed. The failure reasons of the support structure were analyzed, and the relevant support principles were proposed. The research results can provide scientific references for the stability control of roadways excavated in jointed rock mass.

Rock burst is a common mine disaster often accompanied with casualties and property damage. In order to effectively predict and prevent the rock burst occurrence, an effective and accurate method for predicting rock burst is necessary. This paper first establishes the relationship between the drilling cuttings and the releasable elastic deformation energy. However, the traditional drilling cutting method has the defect that the drilling depth cannot reach the stress concentration area and the drilling cuttings cannot accurately reflect the internal stress variation in the deep part of coal body. So, an improved drill cutting method is presented to make up for these defects. Finally, the combined monitoring method based on the improved drilling cutting method and the microseismic monitoring method is established. It not only overcomes the limitations of a single prediction method but also effectively utilizes the advantages of improved drilling cutting method and the microseismic monitoring method. And this combined monitoring method is applied to the No. 3302 coalface of Xingcun Coal Mine. The obtained results indicate that the combined monitoring method can improve the prediction capabilities of the rock burst and provide novel insights for preventing the rock burst occurrence.

Uniaxial compression experiments were carried out on a combination of 12 different lithology and different coal-rock height ratios to study the effects of lithology and rock-coal height ratio on the mechanical properties and impact effects of the composite. The mechanical constitutive models of coal, rock-coal-rock combination were used to analyze the instability process of the combined body and the evolution of physical parameters such as displacement, acceleration, stiffness, energy of various parts during the loading process. The criterion for the stability and instability of the combined body with the stiffness of post-peak of coal and the stiffness of rock unloading as the basic parameter was proposed. The results show that with the decrease of rock-coal height ratio, the failure types of the combined body are “clastic” complete failure, “Y-type” semi-complete failure, “local” incomplete failure (“clastic”, “Y-type” and “local” refer to the failure form of the specimens, complete failure, semi-complete failure, and incomplete failure refer to the failure degree of the specimens), and the compressive strength and elastic modulus of the combined body are reduced, and the impact energy index of the combined body is increased; the harder the rock components in the combined body are, the greater the compressive strength, elastic modulus and impact energy index of the combined body are; the failure state of the combined body is determined by the post-peak stiffness λ of the coal, and the contrast relationship between the stiffness and the rock stiffnesses k₁, k₂ of the roof and floor. After the peak is unloaded to the point S where the change rate of the stiffness of the coal curve meets ${\lambda }^{\prime }\ge k_1{k}_2\ddot{m}/\left[\left(k_1+k_2\right){\dot{u}}^2\right]$, the combined body changes from stable failure to unstable failure. The release of the roof and floor during the failure of the combined body is proposed. The ratio α of the energy released by the roof and floor to the coal consumption energy is used as an evaluation index of outburst proneness under coal and rock combination, and the criterion is proposed.