In order to obtain the characteristics of the effects of cyclic impact loading on the damage of coal-rock in the presence of a local static load constraint, the evolution of the damage factor and the fracture rate during the process and incremental cyclic impact on raw coal and briquettes has been studied. Experimental results show that the presence of local static load restraint improves the impact resistance of the coal-rock, and the damage factor of the coal-rock shows obvious zoning characteristics. When the coal-rock is in an elastic state, the partition with a larger static load restraint area has stronger impact resistance, when the coal-rock is in a plastic state, the partition with a larger static load restraint area has a weaker impact resistance. Increasing impulsive cyclic im- pacts have a higher damage efficiency to coal-rock than constant impulsive cyclic impacts. The difference in rock breaking efficiency between the two cyclic impact methods is mainly reflected in the partition with the largest constrained area. The crack propagation on the coal-rock surface is more consistent with the partition charac- teristics of the damage factor. When the static load constrained zone is in an elastic state, the static load has an inhibitory effect on the crack growth. When the static load confinement zone is in a plastic state, the cracks mainly propagate in the static load confinement zone, and the constrained zone mainly consists of tensile cracks that grow in the vertical direction, while the cracks in the non-constrained zone mainly grow in an oblique direction. Finally, fracture mechanics was applied to analyze the failure type of the sample.

In order to study the mechanism of the dual side roof cutting technology on the composite disaster of gas and coal spontaneous combustion in goaf, a model for the evolution of porosity and permeability in the dual side roof cutting working face was constructed. The location of the occurrence of the compound disaster of gas explosion and coal spontaneous combustion under the double-sided roof cutting mode was studied, and the sensitivity of the evolution pattern of the compound disaster area to the amount of air supply and gas gush was summarized. The results indicate that the top cutting pressure relief technology significantly reduces the permeability of porous media, and the sensitivity of the goaf on the intake side to airflow disturbances is significantly reduced. As the volume of air supply increases, the distance between the gas explosion risk area and the coal spontaneous combustion risk area gradually decreases, and the probability of composite disaster areas is 0. The increase of air supply and gas emission makes the gas concentration in the middle and deep goaf increase in an exponential function, and the width of the gas explosion risk area increases gradually. When the outflow reaches 40 m3/min,there is no composite disaster zone, indicating that the rapid increase in outflow inhibits the occurrence of composite disasters.

Positive pressure effect is the result of rapid urban development in recent years, which leads to over-exploitation of karst groundwater, coupled with the emergence of extreme weather (such as heavy rainfall, the increase in the duration of heavy rainfall), leading to the sharp rise of karst water level, the gas in the karst cavity can not be discharged in time to form a high positive pressure in the soil cavity and promote the destruction of the soil layer, which then induces a series of phenomena, such as karst subsidence. As a new collapse mechanism, the positive pressure effect causes geological disasters that seriously affect the safety of people's lives and properties in karst regions. In order to study the damage characteristics and evolution characteristics of karst soil cavities under positive pressure effect, this study is based on the ASCII text provided by FLAC itself, and the orthotropic simulation computation compilation program, which realizes the finite element analysis in FLAC3D, and focuses on the inhomogeneous change of soil displacement, redistribution of stresses, and plastic damage of karst soil cavities in different evolution stages under the action of positive pressure, and summarizes the characteristics and laws of stress, strain and damage in plastic zone of karst soil cave at different stages of evolution. The results will play a positive role in further investigating the potential mechanical effects, development mechanism and critical warning conditions during the evolution of covered karst soil caves, and also have important scientific research value in deepening the theory of prevention and control of collapse disasters in covered karst soil caves.

Comprehensive research methods such as literature research, theoretical analysis, numerical simulations and field monitoring have been used to analyze the disasters and characteristics caused by the linkage failure and insta- bility of the residual coal pillars-rock strata in multi-seam mining. The effective monitoring area and monitoring design method of linkage instability of residual coal pillar-rock strata in multi-seam mining have been identified. The evaluation index and the risk assessment method of disaster risk have been established and the project cases have been applied and validated. The results show that: ①The coal pillar will not only cause disaster in single- seam mining, but also more easily cause disaster in multi-seam mining. The instability of coal pillars can cause not only dynamical disasters such as rock falls and mine earthquakes, but also cause surface subsidence and other disasters. ②When monitoring the linkage instability of residual coal pillar-rock strata, it is not only necessary to consider the monitoring of the apply load body (key block), the transition body (residual coal pillar) and the carrier body (interlayer rock and working face), but also to strengthen the monitoring of the fracture development height (linkage body). ③According to the principles of objectivity, easy access and quantification, combined with investigation, analysis, and production and geological characteristics of this mining area, the main evaluation indexes of the degree of disaster caused by linkage instability of residual coal pillar-rock strata are determined as: microseismic energy, residual coal pillar damage degree, fracture development height. And the evaluation index classification table was also given. ④According to the measured value of the evaluation index, the fuzzy comprehensive evaluation method was used to calculate the disaster risk degree in the studied mine belongs to class III, that is, medium risk level. The corresponding pressure relief technology was adopted on site, which achieved a good control effect, and also verified the accuracy and effectiveness of the risk evaluation results.

The stability of inclined shaft lining structure (ISLS) in complex water-rich strata is affected by many factors, such as water pressure, joint, soft rock, lining corrosion and so on. The instability of the ISLS will affect the safe and efficient coal mine production. Bathe sed on the geological conditions of the Xiaobaodang coal mine, this paper tested the evolution characteristics of concrete composition in long-term water seepage areas and revealed the influence mechanism of corrosion weakening of shaft lining (SL) in water-rich strata. Meanwhile, transient electromagnetic, ground penetrating radar, and infrared monitoring are used to detect the water-rich zones, and damage zones of surrounding rock and lining water seepage zones, and a three-level safety evaluation model for the instability risk of ISLS is constructed. Water abundance of the surrounding rock, surrounding rock deterio- ration, and shaft lining seepage were the specific indicators in the model. The main inclined shaft (MIS) in the studied coal mine is divided into three levels: non instability risk zone, potential instability risk zone, and high instability risk zone. According to the evaluation results, comprehensive prevention and control measures of “hydrophobic hole drainage” and “back-lining grouting” are adopted for the water inrush source and the sur- rounding rock micro-crack water channel. The precise prevention and control of ISLS is realized. The research results also provide a reference for the stability evaluation of ISLS and the accurate prevention and control under similar conditions.

In order to predict the coal outburst risk quickly and accurately, a PCA-FA-SVM based coal and gas outburst risk prediction model was designed. Principal component analysis (PCA) was used to pre-process the original data samples, extract the principal components of the samples, use firefly algorithm (FA) to improve the support vector machine model, and compare and analyze the prediction results of PCA-FA-SVM model with BP model, FA-SVM model, FA-BP model and SVM model. Accuracy rate, recall rate, Macro-F1 and model prediction time were used as evaluation indexes. The results show that: Principal component analysis improves the prediction efficiency and accuracy of FA-SVM model. The accuracy rate of PCA-FA-SVM model predicting coal and gas outburst risk is 0.962, recall rate is 0.955, Macro-F1 is 0.957, and model prediction time is 0.312s. Compared with other models, The comprehensive performance of PCA-FA-SVM model is better.