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Many coal mines are being abandoned for economic and environmental reasons in China. The repurposing of abandoned open-pit coal mines into pumped storage hydropower (PSH) can help with the storage of renewable energy, improve mine environments, and provide added economic value. Construction of PSH plant will change the water level of the abandoned pit, which is envisaged as the lower reservoir, thus influencing the slope stability. In this study, the Fushun West Open-Pit coal mine was taken as an example. Borehole investigation and tilt photogrammetry were used to obtain the rock mass quality and volume of the abandoned pit. A natural lake, dumps, and another open-pit mine are envisaged as the upper reservoir, which could bring 40, 3,200, and 2,000 MW electricity installed capacity, and −295 m, −200 m, and −150 m water levels in the lower reservoir. The numerical analysis software GeoStudio was used for slope stability analysis considering the hydraulic effect under different water levels. A potential landslide risk may happen in several zones under specific water levels. Further imperviousness and reinforcement work is needed to guarantee slope stability for PSH plant construction in the Fushun West Open-Pit coal mine.

The characteristics and evolution of the geo-stress field are the research bases of overburden migration, roadway surrounding rock stability, and dynamic disaster prevention in deep coal mines. However, the present understanding of mine geological stress mainly depends on measurements obtained at a few discrete points, leading to obviously insufficient knowledge of the geo-stress field in the whole mining area. In this study, a novel optimal inversion analysis model of the geo-stress field was established based on multiobjective constraint technology, solid mechanics, optimization analysis, and stress inversion theory. Then, a 3D numerical simulation analysis model with large-scale general finite element software as the solver was constructed for the optimization of the boundary conditions of the geo-stress field. This simulation model identified the key links between the stress field boundary loads and the actual measurement data by directly solving the multiobjective optimization problem. Six on-site measurement points were selected at the Xinji No. 1 mine, and the magnitude and orientation of the geo-stress at these points were measured with the hollow inclusion strain gauge method. The distribution of the geo-stress and the main influential factors were then analyzed numerically. The results of the study are of great significance for investigating the geo-stress distribution.

Determining a reasonable barrier pillar along gob-side entry of spontaneous combustion coal seam is of great significance to the prevention of spontaneous combustion. In this paper, considering the actual situation of 4301 and 4302 working faces of II-class spontaneous combustion coal seam in Changheng Mine, the characteristics of rock mass collapse and mining-induced stress redistribution of barrier pillar and adjacent area were analyzed, the cusp catastrophe model of coal pillar instability and the theoretical model of limit width of coal pillar air leakage spontaneous combustion were established, and a measurement scheme of side abutment pressure in 4301 working face was carried out. The theoretical model of the coal pillar along the gob-side entry shows that its instability is related to density of overlying strata, physical and mechanical parameters of coal body, dip angle of coal seam and weak face, and buried depth and mining width of working face. And the coal pillar in 4302 working face will be unstable if the width a ≤ 6.8 m . Field measured data shows that 2-8 m is the stress-relaxation area of side solid coal. Then, the width of coal pillar was determined as 7 m. The maximum displacement of rib-to-rib and roof-to-floor of 4302 tailentry was 520 mm and 280 mm, respectively. The coal spontaneous combustion (CSC) observation monitoring results showed that the carbon monoxide volume fraction was in the normal range during the entire process of mining, and no other signs of gas were found. The research results can provide a reference for the barrier pillar designing in the mines under similar conditions.

The cement used in roadway is in the state of long-term compression, and its creep characteristics have been extensively studied. However, the cement paste will be affected by stress after construction and cause early damage, and the creep behavior after damage has not been involved. To solve this problem, 5 groups of 10 cement stone specimens were prepared for early damage and post-damage creep tests. The results show that the damage amount at each stage can be calculated by establishing a complete damage solving equation, and the creep behavior after damage can be effectively characterized by the modified Nishihara model after introducing damage factors. With the decrease of the stress ratio (100% ~ 60%), the axial strain, transverse strain, Poisson's ratio and the damage amount of the cement stone specimen decrease, while the elastic modulus increases. The 80% stress ratio (the damage amount is 0.50) of early cement stone specimen is the damage threshold value, and the effect of early damage below this value on later creep property is far less than that of the damage above the threshold value. The internal cracks of the specimen under the acoustic emission observation increase with the increase of the damage amount from compaction to generation of fine cracks and then gradually penetrate to failure. With the decrease of damage amount, the creep failure strength of cement stone specimen showed a trend of rapid increase at first and then stable, while the primary damage strain and primary creep strain showed a trend of rapid decrease at first and then slow decrease, both of which changed at 0.50 damage amount. The instability modes of cement stone specimens are divided into energy storage instability and dissipative energy instability. The stress concentration of high and low damage specimens occurs at large and small cracks respectively in the creep stage.

Steeply dipping coal seams, which are widespread in western China, are considered to have complex mining conditions. The development of such a seam plays an important role in regional economic development. Some steeply dipping coal seams are distributed at close distances. For closely located coal seam groups, China generally adopts the downward mining method for mining. Aiming at the problems of the appearance of ground pressure such as coal wall spalling and roadway squeezing deformation of a fully inclined working face under a goaf in a close coal seam group, the mining of the 5th and 4th coal at the steeply dipping coal seam in Panbei Mine was established as the engineering background. The mechanical model of the coal zone plastic area in front of the 12124 working face under the goaf and the distribution characteristics of abutment pressure in front of the coal wall were obtained. The working surface layout and coal rock physical and mechanical parameters were derived based on field observation records and indoor rock mechanics experiments. A numerical analysis model based on the fast Lagrangian analysis of Continua 3D software was constructed, and the surrounding rock mechanics during the 12124 working face mining process was simulated. The stress distribution characteristics of the front and back of the 12124 working face under the goaf were obtained, magnitude and location of the stress peak were determined, and superposition mechanism of the support pressure evolution of the fully mechanized thick seam under the goaf was revealed. Through field measurement of the distribution of the working resistance of the supports, the maximum working resistance, position of the supports, and accuracy of the theoretical calculation and numerical simulation were verified within the error range. Furthermore, stability control technology of the surrounding rock of the stope, roof falling, and roadway under this condition was proposed and implemented. Good economic and technical effects were obtained, which ensured safe mining at these working faces.