During the mining process of impact-prone coal seams, drilling pressure relief can reduce the impact propensity of the coal seam, but it also reduces the integrity and strength of the coal mass at the side of the roadway. Therefore, studying the mechanical properties and energy evolution rules of coal samples containing holes and filled structures has certain practical significance for achieving coordinated control of coal mine rockburst disasters and the stability of roadway surrounding rocks. To achieve this aim, seven types of burst-prone coal samples were prepared and subject to uniaxial compression experiments with the aid of a TAW-3000 electro-hydraulic servo testing machine. Besides, the stress–strain curves, acoustic emission signals, DIC strain fields and other data were collected during the experiments. Furthermore, the failure modes and energy evolutions of samples with varying drilled hole sizes and filling materials were analyzed. The results show that the indexes related to burst propensity of the drilled coal samples decline to some extent compared with those of the intact one, and the decline is positively corelated to the diameter of the drilled hole. After hole filling, the strain concentration degree around the drilled hole is lowered to a certain degree, and polyurethane filling has a more remarkable effect than cement filling. Meanwhile, hole filling can enhance the strength and deformation resistance of coal. Hole drilling can accelerate the release of accumulated elastic strain energy, turning the acoustic emission events from low-frequency and high-energy ones to high-frequency and low-energy ones, whereas hole filling can reduce the intensity of energy release. The experimental results and theoretical derivation demonstrate that hole filling promotes coal deformability and strength mainly by weakening stress concentration surrounding the drilled holes. Moreover, the fillings can achieve a better filling effect if their elastic modulus and Poisson’s ratio are closer to those of the coal body.

Numerical simulations have often been used in close-distance coal seam studies. However, numerical simulations can contain certain subjective and objective limitations, such as high randomness and excessively simplified models. In this study, close-distance coal seams were mechanically modeled based on the half-plane theory. An analytical solution of the floor stress distribution was derived and visualized using Mathematica software. The principal stress difference was regarded as a stability criterion for the rock surrounding the roadway. Then, the evolution laws of the floor principal stress difference under different factors that influence stability were further examined. Finally, stability control measures for the rock surrounding the roadway in the lower coal seam were proposed. The results indicated the following: (1) The principal stress difference of the floor considers the centerline of the upper coal pillar as a symmetry axis and transmits radially downward. The principal stress difference in the rock surrounding the roadway gradually decreases as the distance from the upper coal pillar increases and can be ranked in the following order: left rib > roof > right rib. (2) The minimum principal stress difference zones are located at the center of the left and right “spirals,” which are obliquely below the edge of the upper coal pillar. This is an ideal position for the lower coal seam roadway. (3) The shallowness of the roadway, a small stress concentration coefficient, high level of coal cohesion, large coal internal friction angle, and appropriate lengthening of the working face of the upper coal seam are conducive to the stability of the lower coal seam roadway. (4) Through bolt (cable) support, borehole pressure relief, and pregrouting measures, the roof-to-floor and rib-to-rib convergence of the 13313 return airway is significantly reduced, and the stability of the rock surrounding the roadway is substantially improved. This research provides a theoretical basis and field experience for stabilizing the lower coal seam roadways in close-distance coal seams.

In order to reveal the impact mechanical properties and their key influencing factors of the bolted rock under the lateral impact load, through the lateral drop hammer impact test, the time-history curve of impact force, axial force of the bolt, and surface strain of the sample under different combination types of influencing factors is obtained, and the whole process of deformation and failure of the bolted rock is recorded. The test results show that the material of the bolt has a significant influence on the impact force and axial force of the bolt. There is a positive correlation between bolt strength and impact peak and impact attenuation slope and a negative correlation between bolt strength and impact action time. The effect of prestress on the impact resistance of the bolted rock was also evaluated by the test which suggested that prestress of the bolt can significantly reduce both impact time and bolt axial force of the bolted rock but has limited effect on the impact force. It was also found that the time-history curve of the impact force of anchoring rock mass had significant difference with full-length anchoring and nonanchoring. Compared with the nonanchoring bolt, the full-length anchored rock mass has a larger impact peak and shorter action time, which means that the impact resistance of the full-length bolted rock has a certain degree of weakening. Through scientific research, determining the reasonable bolt material, prestress value, and anchorage style can improve the impact resistance of the sample.

The mining area in western China is ecologically sensitive. Coal mining can cause the formation of ground fissures, leading to geological disasters and further accelerating the process of land desertification. In this study, the working face of non-coal-pillar mining in the aeolian sand area was considered as the research object. The movement and deformation law of overlying strata were investigated through field measurements, theoretical analysis, and numerical simulation, and the mechanism governing the self-healing characteristics of ground fissures was revealed. The results demonstrated that the surface angular parameters were lower. This implies that the surface movement and the degree of deformation in non-coal-pillar mining in the aeolian sand area are significant, with a large mining influence range and rapid surface subsidence speed. After the mining of the working face, the resulting failure form of the overlying rock was asymmetric. Boundary ground fissures are typically located within the boundary of the working face, and no outward expansion is primarily observed. Dynamic ground fissures have “waviness” morphological characteristics and asymmetric “M” type development characteristics. A location model as well as a development cycle model of dynamic ground fissures were established for the first time, which can be used to predict the location and period of ground fissures. Based on the motion characteristics of hinged rock block structures, the mechanical mechanism of the self-healing phenomenon of dynamic ground fissures was revealed. A partition monitoring mode of working faces without coal pillar mining was proposed for the first time, which can reduce a lot of manpower and material resources. The coal mining subsidence basin is divided into a natural restoration area and an artificial restoration area. The combination of natural restoration and artificial guidance was used to control the ground fissures and reduce the associated costs. The research conclusions can provide a basis for mining damage evaluation and ecological environment protection in the aeolian sand area.