The successful retaining of the gob‐side entry under a thick and hard roof stratum is difficult because of the high pressure present and complex construction technology commonly used. To solve this problem, a new type of gob‐side entry supporting system is proposed in this paper. This system is mainly composed of concrete‐filled steel tubular columns (CSTCs), flexible cushion, and gob isolation structures. This new supporting system combines the high‐strength support of CSTCs with the flexible support of cushion bodies and is simple to construct, enabling fast and efficient gob‐side entry retaining under a thick and hard roof stratum. The range of the roof strata controlled by gob‐side support structures is determined for a case study, and a calculation formula for the gob‐side support resistance is established. Through theoretical and experimental research, a reasonable calculation formula for the choice of CSTC is also established. The CSTC structure ultimately selects Φ194 × 8 mm hollow steel tubes and C40 grade concrete for use in a field application, which can provide 4814 kN of supporting force. A simple on‐site construction process is designed for the field application, and the time required for entry retaining per meter is only approximately 40‐45 minutes. This application shows that the new technology controls the deformation of the retained entry very well; the final deformation stabilizes at 412 mm, which meets the engineering requirements.

In order to study the development height of the water-conducting fracture zone in a fully mechanized top coal caving face. The E2311 working face of Gaohe Coal Mine was chosen as the research object, and the combined-strata structure and the rock layer synergistic movement mechanism were determined by combining engineering geological investigation and theoretical analysis. The height of the water-conducting fracture zone at the working face was calculated based on the combined-strata structure, and then the theoretical results were verified by numerical simulation and field measurement. The results show that after the coal seam is extracted from the working face, the movement of the overlying rock layers is in the form of bending and sinking movement of the rock layer group as a unit. Each rock layer group is controlled by a supportive lower layer with greater thickness and strength, driving the upper layers of weaker rock layers to synchronize and coordinate the movement; the sinking curvature is the same, after the lowermost support layer is bent and broken, its overlying weaker rock layers will move and break at the same time. The height of the water-conducting fracture zone of the working face were obtained by theoretical calculation, numerical simulation, and field measurements, which are 83.82 m, 84.3 m, and 86.6 m, respectively. The results are nearly consistent, thus the prediction of the height of the water-conducting fracture zone under the combined-strata structure is more accurate.

The supporting technology of retaining small coal pillars in a double roadway layout can effectively relieve the tension of mining and excavation replacement and improve the coal recovery rate. The critical difficulty is that the supporting structure on both sides of the small coal pillar has not established an effective mechanical connection, and the improvement of the bearing capacity of the coal pillar is limited, so it is difficult to achieve long-term stability control of the small coal pillar. Taking the 301 and 302 working faces of Gaojiapu Coal Mine as the engineering background, this paper first constructs the overburden structure model of the whole process of mining with small coal pillars in a double roadway layout, obtains the load calculation and strength calculation methods of small coal pillars through the analysis of the mechanism of small coal pillars surrounding rock mechanics, and gives the selection design of support parameters of anchor cables and concrete filled steel tubular piers; Secondly, the influence rules of physical and mechanical parameters such as axial load, elastic modulus and residual strength of anchor solid under different reinforcement methods and the lateral reinforcement coefficient of anchor cable are obtained through experiments. Finally, the support parameters and the coal pillar width are reasonably designed. The field monitoring data show that the reinforcement technology of a small coal pillar with anchor cable as the main body can effectively control the deformation of the small coal pillar, which has specific guiding significance and application value for solving the long-term stability control problem of small coal pillar under the influence of mining.

To solve the problem of controlling the stability of small coal pillars under the mining disturbance of the adjacent working face, the fourth panel 403 and 404 working faces of the Gaojiabao coal mine with two mining roadways is taken as the object of this research. The comprehensive research method of combining mechanical theory analysis, coal dynamic disturbance experiments and field engineering practice was adopted. First, the analysis determined the magnitude and frequency of fracture‐related disturbance loading on the overburden roof of the working face; next, the strain and stress threshold indicators of the coal body, sensitive to the external disturbance load of 10³ J magnitude (continuous disturbance deformation), were tested and obtained through a self‐developed rock creep disturbance experimental system, and the stress threshold indicators of coal body specimens sensitive to creep disturbance were defined as the long‐term strength. Then, a coal pillar‐roof mechanics structure model was established in the premining and postmining areas of the working face, and the overlying support pressure on the coal pillar body was analysed. Finally, a small coal pillar composite reinforcement support technology with ‘two‐way buttressing anchor cable for pressure reinforcement + steel pipe concrete pier column + overhead roof break’ was designed to ensuring that the coal pillar body would not be destabilised by cumulative disturbance and large deformation under disturbance. According postmining area support capacity calculations, the support loading acting on the coal pillar is approximately 17593 kN, with the stress being 2.93 MPa; and the factor of safety is approximately 1.23. After engineering practice application of this approach, the vertical deformation of the small coal pillar body and side heave disturbance deformation were effectively controlled during the working face mining disturbance, the vertical deformation of the reinforced coal pillar was only 187 mm, and the side heave deformation was finally stabilised at approximately 124 mm, which maintained good stability.

To solve the ground subsidence problem associated with thick coal seam mining under the railway in the Tangshan Mine, the technology of overburden strata separation-zone grouting (OSSG) was proposed. Based on the analysis of the full height overlying strata structure in the range of the six working face areas of the second mining district, the spatial distribution characteristics of the separation zone within the overlying strata are obtained after fully mining the six working faces. Then, emphasis was placed on the selection ratio of grouting materials and the hydrodynamic properties of different grout types, and grouting grout with a high concentration, slow precipitation rate, and good stability was obtained by taking fly ash and local clay as aggregates. The designed grout concentration was approximately 40%; the bulk density was approximately 1.20; and the clay content in the aggregates was approximately 40–50%. The separation-zone grouting plan was designed for the six working faces, and continuous grouting technology with the characteristics of multiple separation zones within the full-height section with a large flow and a high concentration was proposed to form a complete grouting system and reasonable grouting process. After engineering verification, the technology has an ash injection ratio of 24.2%, a grouting ratio of 100.3%, and a reduction in the ground subsidence ratio of 51.5%, effectively reducing mining damage to the ground surface and ensuring the safe operation of ground surface railways. Simultaneously, this advancement improves the resource recovery rate of coal mines and provides greater benefits for mining enterprises.