With the increasing mining depth, the dynamic disaster of coal and gas outbursts in coal mines has become increasingly prominent, and the bursting liability of coal and rock mass in deep coal seam mining is a necessary condition for the occurrence of rock burst and an important index to measure the failure of coal and rock mass. Thermal damage leads to rock instability and failure, which seriously influences the safe and efficient operation of coal mines. To investigate the effect of thermal damage on the bursting liability of deep coals, the burst tendency index of standard coal was measured after subjecting it to thermal damage at different temperatures. The effects of different thermal damage temperatures on the uniaxial compressive strength index, dynamic failure duration, stiffness ratio index, effective impact energy index, residual energy index change rate, and impact energy velocity of the coal and the influence of the post-peak failure mode of the coal were evaluated. The results revealed that the uniaxial compressive strength of the coal generally decreased with increasing thermal damage temperature. At temperatures above 200 °C, the strength significantly decreased. The comprehensive impact property index indicated that, with increasing thermal impact temperature, the burst tendency first increased up to the peak value at 200 °C and then gradually decreased. With the increase in the thermal damage temperature, the burst tendency decreased and disappeared in the temperature range of 250–300 °C, and the failure mode of the coal changed from brittle failure to brittle plastic failure, and finally ductile failure. The influence of thermal damage on coal bursting liability is studied, which provides a theoretical basis for preventing and controlling coal impact ground pressure hazards.

In order to study the effect of a double-machine parallel circulation air curtain in intercepting wind flow in a mine roadway, the air curtain jet angle and full fan pressure were analyzed. Taking a metal mine roadway as the engineering background, Fluent numerical simulation technology was used to establish an equi-proportional physical model of the original roadway, and a K45-6 axial flow fan was selected to numerically simulate the flow field inside the original roadway, which was analyzed from three aspects: isolation pressure difference, air leakage volume and wind choke rate. The results show that when the full pressure of the fan is fixed, with an increase in the jet angle of the air curtain, the separation pressure difference and the wind choke rate show a trend of first increasing and then decreasing, and the air leakage volume shows a trend of first decreasing and then increasing. With an increase in the air curtain jet angle, the air curtain convergence gradually forms a complete air curtain, but when the air curtain jet angle continues to increase, the air curtain cannot effectively block the wind flow due to the transverse pressure from the roadway. When the jet angle is too small or the full pressure of the fan is too large, the phenomenon of induced air flow will occur, and the two-machine parallel air curtain will direct the air downstream of the roadway to upstream and no longer intercept the roadway air flow. After comprehensive analysis, the effect of wind control is obvious to set up a double-parallel air curtain in the roadway, and the optimal combination of the roadway air curtain is 30° for the full pressure blade of the fan and 30° for the jet angle.

Aiming to investigate the seepage-mechanics coupling characteristics of coal under complex stress conditions and their impact on coal mine engineering safety, and providing theoretical and experimental support for key issues such as gas disaster prevention, efficient coalbed methane development, and surrounding rock stability control, a high-precision triaxial fluid-solid coupling test system was independently developed based on advanced image measurement technology, By integrating multi-physical field sensing modules and a real-time data acquisition system, this system enables synchronous monitoring and analysis of the dynamic mechanical responses and seepage characteristics of coal samples under coupled axial pressure, confining pressure, and seepage loading. The research first elaborates on the core components and working principles of the system, including the triaxial loading device, seepage pressure control system, digital image acquisition unit, and data processing algorithms. Subsequently, through coal failure tests designed under different stress paths and seepage conditions, combined with the non-contact strain measurement and full-field deformation visualization capabilities of image measurement technology, the study reveals the synergistic evolution laws and disaster mechanisms of coal deformation and seepage. The experimental results demonstrate that the system can accurately capture the changes in seepage-mechanics parameters during the entire process of coal fracture initiation, propagation, and penetration, quantitatively characterizing key indicators such as effective stress coefficients and dynamic permeability evolution. This provides an experimental basis for establishing a more comprehensive fluid-solid coupling theoretical model. Furthermore, the intelligent analysis method based on image measurement technology significantly improves data acquisition efficiency and reliability, overcoming the limitations of traditional point-based measurements. This study not only provides an important technical approach for the safe mining of deep coal resources and the optimization of gas extraction but also offers a referential methodology for research on fluid-solid coupling issues in similar underground engineering projects.

To investigate the effects of barrier spacing gradients on gas explosions in confined spaces, a large eddy simulation (LES) based on the Charlette turbulent combustion model was employed to simulate the coupling process of explosion flame, turbulent flow, and pressure wave under multi-stage obstacles with spacing gradients of 0, 0.005, 0.010, and 0.015. The results indicate that vorticity increases on the obstacle surfaces as the flame passes through them, accompanied by backflow vortices. When the spacing gradient reaches 0.010 and 0.015, the flame front becomes sharper, and both the flame propagation velocity and the rate of change in flame surface area are higher in the later stages of the explosion. The peak values and corresponding areas of flame propagation velocity, as well as the peak rate of flame surface area change, follow the descending order of conditions: 0.015, 0.010, 0.005, and 0. Furthermore, a higher obstacle spacing gradient enhances combustion efficiency and promotes pressure accumulation, leading to an increase in the maximum overpressure with larger spacing gradients.

Liquid nitrogen freeze-thaw has a positive effect on increasing the permeability of coal and rock.In order to study the pore characteristics and mechanical characteristics of water-saturated coal rock under liquid nitrogen cycle freezing and thawing, nuclear magnetic resonance, triaxial loading and seepage experiments were carried out on water-saturated frozen coal rock.The results show that: (1) After the freeze-thaw cycles, various types of pores in the coal and rock gradually develop. This is because liquid nitrogen freeze-thaw can promote the generation and development of micro-pores, and expand and fuse them into medium and large pores, thereby forming a fracture network; (2) After five freeze-thaw cycles, the porosity of the coal and rock increased from 1.089% to 2.571%, and the permeability increased from 0.771 mD to 19.884 mD. Compared with the initial freeze-thaw, the number of adsorption pores in the coal and rock increased from 1.15 times to 2.82 times, and the number of seepage pores increased from 1.80 times to 6.23 times; (3) After multiple freeze-thaw cycles, the internal fracture structure of the coal and rock gradually expands and fuses to form new fractures. The generation of new fractures releases the bound water in the adsorption pores to larger pores and transforms it into free water, resulting in a significant increase in the porosity and permeability of the coal and rock; (4) With the increase in the number of freeze-thaw cycles, the rate of energy accumulation in the coal and rock before the peak gradually decreases.