Providing support for deep soft rock roadways under dynamic pressure is a major technical challenge. In this study, the distribution characteristics of surrounding rock-bearing structure of such roadways were systematically examined using theoretical analysis and numerical simulation. Based on the control effect of different support methods on the surrounding rock-bearing structure; a reinforcement scheme for deep dynamic soft rock roadway was proposed and applied. The results indicate that: (1) by increasing the supporting strength of the internal bearing structure, cohesion, and internal friction angle of the surrounding rock, and by reducing the influence of mining, making the external bearing structure close to the roadway and reducing the thickness of the bearing structure, can improve the bearing capacity of the shallow surrounding rock in the roadway; (2) under the conditions of dynamic load and creep of the surrounding rock; the deformation of the rock increases significantly; external bearing structure is far away from the roadway, and thickness of the bearing structure increases; anchor cable support and floor pressure relief effect better control over the roof and the roadside deformation and floor heave, respectively; and the thickness of the corresponding external bearing structure is reduced by 30.84% and 41.50%, respectively; and (3) based on the application, the zonal reinforcement scheme of “fix cable to shed, floor pressure relief, deep-shallow composite grouting” is proposed and put into practice, with good results. The results of this study can provide theoretical support and reference for the determination of supporting parameters in deep roadways.

Pingdingshan mining area is one of the typical deep mining areas in China, and most of the mines in this area are troubled by the difficulties of the deep-soft-rock roadway support. Based on the concept of synergistic interactions of the interior and exterior bearing structure of the surrounding rock and, considering the specific geological conditions of the research site, we establish the mechanical model of the interior and exterior bearing structure of the roadway. Based on numerical simulation, we reveal the influence of main factors, such as support strength and mechanical characteristics, of surrounding rock on the distribution and evolution of the interior and exterior bearing structure. We found that increasing the support strength and mechanical parameters of surrounding rock can make the exterior bearing structure close to the roadway enhance the bearing characteristics of the interior and exterior bearing structure and improve the roadway stability. The distribution characteristics of the interior and exterior bearing structure of the roadway under six different support strengths and six different grouting parameters were systematically investigated by field measurements. According to the field test results, an effective strategy for controlling the deep-soft-rock roadway is proposed, which provides a good reference for surrounding rock control of the deep-soft-rock roadway in the Pingdingshan mining area and mines with similar mining conditions.

In order to investigate the effects of elliptical defects on rock failure under ultrasonic vibrations, ultrasonic vibration tests and PFC^2D numerical simulations were conducted on rocks with single elliptical defects. The research results indicated that the fracture fractal dimension, axial strain, and crack depth of specimens with elliptical defects at 45° and 90° were the smallest and largest, respectively. The corresponding strain and fractal dimension showed a positive linear and logarithmic function relationship with time. The maximum crack depth of 46.50 mm was observed on the specimens with an elliptical defect angle of 90°. Specimens with elliptical defects at 0°, 30°, 75°, and 90° exhibited more dense and frequent acoustic emission events than those with elliptical defects at 15°, 45°, and 60°. During the ultrasonic vibration process, the maximum total energy (87.86 kJ) and energy consumption coefficient (0.963) were observed on specimens with elliptical defect angles of 30° and 45°, respectively. The difference in the stress field led to varying degrees of plastic strain energy in the specimens, resulting in different forms of crack propagation and triggering differential acoustic emission events, ultimately leading to specimen failure with different crack shapes and depths. The fractal dimensions of elliptical defect specimens under ultrasonic vibration have a high degree of consistency with the changes in axial strain and failure depth, and the fractal dimension of defect specimens is positively correlated with the degree of failure of defect specimens.

Coal seam mining induces disturbances in underground floors, leading to plastic failure, which presents significant safety risks, particularly in areas with underlying pressurized water. Accurately assessing the maximum depth of such floor failure is crucial for ensuring safe mining operations. This study investigates the evolution of apparent resistivity in the floor of the 4,301 working face using the network parallel electrical method. The observed maximum failure depth was found to be 19.3 m. Based on these measurements, the plastic slip theory for a homogeneous rock layer was applied, incorporating mining parameters such as burial depth and mining height. Five mechanical models for plastic slip failure in multi-layer composite floors were developed, with the maximum failure depth calculated to be 18.26 m. The study also explores the impact of factors such as mining height, burial depth, and the internal friction angle of the rock layers on floor failure depth. The results demonstrate that multi-layer composite floors exhibit a 23.1% reduction in failure depth on average compared to homogeneous floors. Numerical simulations confirmed that the maximum failure depth under mining disturbance is 19.2 m, with shear failure identified as the predominant failure mode. The findings from the theoretical analysis, numerical simulations, and field measurements align closely, validating the applicability of the plastic slip theory for multi-layer composite floors. This research provides critical theoretical support for safe mining operations in coal seams above confined aquifers and effective water control strategies.

As a key sustainable green-mining technology, ultra-high-water backfill mining is widely used to control surface subsidence and sustain extraction of constrained coal seams. Focusing on the Hengjian coal mine in the Handan mining area, this study uses physical modeling and industrial tests to clarify surface subsidence under different filling rates and identify the rock layers that hydraulic supports must control at various equivalent mining heights. A method is proposed to improve the filling rate by optimizing the thickness of the hydraulic support canopy through topological analysis. Results show that, compared with a filling rate of 85%, a 90% filling rate reduces subsidence of the basic roof, key layer, and surface by 51%, 57%, and 63%, respectively, while the industrial practice results have verified that the filling rate can significantly control surface subsidence. The equivalent mining height thresholds for instability of the immediate roof and high basic roof at the 2515 working face are 0.44 m and 1.26 m. Reducing the trailing beam thickness by 10 cm can theoretically raise the filling rate of the 2515 working face by about 2%, offering guidance for similar mines.

This study aims to address the pronounced stress concentration in roadway-surrounding rock under conditions of multiple thick and hard roof strata at Xiao jihan coal mine, China. The work was carried out on the 13216 working mining face as the engineering background. A systematic investigation was conducted using a combination of theoretical analysis, numerical simulation, and field experiments. Under double mining disturbance, the lower thick hard roof behaves as a cantilever beam and the upper hard roof strata form a masonry beam structure, producing strong stress transfer to the roadway. The mechanical model indicates a peak stress of 28.90 MPa, 18.34 MPa higher than the in situ stress. Hydraulic roof cutting was designed at the upper thick hard roof horizon. UDEC simulations show that the vertical stress decreases from 26.10 MPa to 13.20 MPa. Field monitoring confirms pressure relief: the non-cutting zone shows a peak of 30.75 MPa, while the roof-cutting zone drops to 22.51 MPa, a 24.62% reduction. The findings of this study provide practical guidance for lateral structure regulation under similar geological and mining conditions.