To study the stability control of stope mining roadways below remaining coal pillars, the present study investigates the destabilization mechanism of coal pillars and roadways in sections under the dual action of supporting pressure on the floor of the remaining coal pillar in the overlying coal seam and the mining at the working face of the lower coal seam and clarify the principle of surrounding rock stability control based on theoretical analysis, numerical simulation, and industrial testing. The results yielded the following findings. After the stope mining of the overlying coal seam working face, the stress transfer of the T-shaped remaining coal pillar significantly increased the vertical stress of the lower coal seam. The lateral support pressure generated by the stope mining at the lower coal seam working face further aggravated the stress concentration in the coal, leading to severe compression-shear failure of the surrounding rock. As the sectional coal pillar becomes wider, the roadway gradually avoids the area of peak superimposed support pressure. The vertical stress curve of the sectional coal pillar shifts from single-peaked to asymmetrically double-peaked, and the stress difference between the two roadway ribs and the stress concentration coefficients decrease continuously. A stability control method of long anchor cable reinforcement support is proposed. In-situ industrial testing showed that the surrounding rock deformation was basically stable during the service period of the 42202 stope mining roadway, thus achieving the stability control of the stope mining roadway.

In order to effectively address stability control technology issues of soft surrounding rock roadways in deep mines. This study analyses the deformation and failure characteristics of the surrounding rock of a −962 m horizontal track roadway with original support conditions based on a severe deformation case that occurred in a mine. Upon establishing a mechanical model of surrounding rock failure zoning for circular roadways, which is based on the relationship between the stress–strain curve of soft rocks and the secondary stress distribution and strength of surrounding rock, this study explores the influence of rock strength indicators, disturbance degree, and support resistance on the stress distribution of the surrounding rock. The failure or instability mechanism of high-stress soft and weak surrounding rock is revealed on this basis. A multi-stage strengthening combined support technology is proposed, which consists of “high-strength prestressed anchor bolt (cable) supports as the core, deep and shallow hole groutings as the foundation, bottom angle, and floor anchorage grouting reinforcements as the key.” Moreover, numerical simulation and engineering practice optimize and verify the support scheme. The results show that after adopting the multi-stage strengthening combined support technology, the deformation of the surrounding rock of the roadways was only 12.6~14.3% of that under the original supporting parameters, and the deformation rate was still less than 0.2 mm/d even after 40 days. The proposed surrounding rock support method realizes the stability control of the roadway, which also has specific reference significance for similar projects.

To investigate the mechanical damage characteristics and energy evolution laws of primary coal–rock combinations with different coal–rock ratios, uniaxial compression tests were conducted. Combined with acoustic emission monitoring results, a comparative analysis was performed on the yield strength, elastic modulus, acoustic emission signal characteristics, failure characteristics, and energy accumulation–dissipation characteristics of five different coal–rock ratio specimens. The study reveals the following: (1) Defect structures and dimensions of coal bodies influence the strength of specimens, with the peak stress and elastic modulus of specimens showing a decreasing trend with an increasing coal–rock ratio. (2) The transitional zone of primary coal–rock composite exhibits distinct interface effects on coal and rock components. Coal-derived stresses manifest as horizontal tensile stresses, promoting deformation at the interface between coal and rock, whereas rock-derived stresses at the interface manifest as horizontal compressive stresses, restricting deformation at the coal–rock interface. Moreover, positions closer to the interface experience stronger limitations due to the interface effects. (3) Coal–rock interface cracks are more developed in the primary coal–rock composite, with multipoint cracking occurring at the interface during failure, and a feedback mechanism between coal and rock failure exacerbates the damage and dynamic manifestation intensity of coal bodies. (4) The acoustic emission signals from single-rock samples indicate shear failure of the specimens. Conversely, the acoustic emission signals from single-coal samples and combinations suggest that tensile failure is the primary destabilizing factor. Moreover, with an increase in the proportion of coal, specimens transition from tensile failure to tensile–shear composite failure.

Based on the comprehensive analysis of wellbore characteristics in a deep shale gas field, the in-situ stress state of the shale reservoir was assessed in this study for the Longmaxi formation in the Dingshan area, Southwestern China. The data obtained from hydraulic fracturing, drilling-induced fractures, and in-situ core testing were used to determine the magnitude and direction of the maximum principal horizontal stress in five wells. Besides, hydraulic fracturing and cross-multipole array acoustic logging (XMAC) were employed to determine the vertical variation of the in-situ stress. Based on the logging interpretation and mechanical test results, the spatial distribution of rock mechanical parameters in the Dingshan area was assessed by the amplitude variation versus offset (AVO) seismic inversion. A 3D heterogeneous mechanical inversion model was realized via the ANSYS and CATIA3D finite element software packages, providing the area in-situ stress field simulation. The depth, fault strike, and position change effects on the main stress, horizontal stress difference, and horizontal stress difference coefficient were numerically simulated. The results show that the maximum principal stress azimuth was mainly concentrated in the NE20°-NE80° sector. Moreover, the development zone of natural fractures was related to the area with the highest principal stress differences. The maximum principal stress variation in the study area was mainly in the compressive range from −135 to −45 MPa, gradually increasing from east to west and south to north. The stress type mainly depended on the depth, fault strike, and rock mechanical parameters, while the stress difference and stress difference coefficient near the fault structure were relatively small. This study’s findings are considered instrumental in improving the borehole stability, determining the casing setting point, and optimizing the well location in deep shale reservoirs with similar geological conditions.

The strong disturbance of upward mining of the short-distance multiseam results in frequent fractures in the coal seam to be mined, jeopardizing the operation safety due to the instability of the surrounding rock of the overlying stope and risks of coal and gas outburst. A lucrative alternative is the downward mining of multiseam, which wide implementation is limited by the lack of reliable data on stress evolution characteristics. In this paper, the evolution, nonlinear interaction, and superposition characteristics of mining-induced stress after multiple pressure relief in the short-distance multi-seam were investigated by the numerical simulation and physical simulation, taking the endowment and mining technology characteristics of group B short-distance multiseam in Pan’er Coal Mine in Anhui Province of China as an example. The numerical and physical models of multiple (2—5 times) mining activities in pressure relief multiseam (with five main coal layers) under downward mining are constructed and implemented with the FLAC3D software and 1 : 100 scaling, respectively. The results showed that a pressure relief arch, which bears and transfers stresses, is formed on the coal seam’s roof and floor. In downward mining, the local arch expands to the long arch, which bearing capacity within the influence range of multiple mining disturbances is weak, and the arch structure is prone to instability. If a coal pillar is left in the upper coal seam after its mining, the lower coal seam mining will switch from the large-scale low-stress area under the goaf to the small-scale high-stress area of nonlinear interaction of the multiple mining stresses with the stress under the coal pillar.