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 freezing and thawing of liquid nitrogen on the mechanical and seepage characteristics of coal rock with different water content values, conventional triaxial loading tests on freeze–thawed coal samples with different water content values were carried out using non-contact digital image processing technology. The research results showed that with the same water content, the peak strength of a liquid nitrogen freeze–thawed coal sample was smaller than that of a non-freeze–thawed coal sample, and the Poisson’s ratio was larger than that of the non-freeze–thawed coal sample; compared with the non-freeze–thawed coal sample, the strain fluctuation and concentration in the stages of compression density, elasticity, yield, and damage were weakened after freeze–thawing by liquid nitrogen, but the local stress concentration was more obvious; the non-freeze–thawed coal sample mainly showed single shear damage, and the damage fissures were inclined fissures with small openings. The higher the water content, the more obvious the tensile damage; with the increase in water content, the permeability of non-freeze–thawed coal samples showed a linear decreasing trend, and the permeability of coal samples was 0.03 × 10^–3 μm² when the water content reached 9%. The permeability of freeze–thawed coal samples showed a non-linear increasing trend, and the higher the water content under the effect of expansion, the faster the permeability growth rate; the permeability of coal samples could reach 6.30 × 10^–3 μm² when the water content was 9%. The results of the study can provide a theoretical guidance for gas permeation enhancement in deep low-permeability coal seams.

This paper is devoted to solving the problem of how to comprehensively control coal seam gas and hydrogen sulfide in the mining face, distributed from the coal seam in abandoned oil wells in coal mining resource areas. The abandoned oil wells of Ma tan 30 and Ma tan 31 in the No. I0104₁05 working face of the Shuang Ma Coal Mine were taken as examples. Through parameter testing, gas composition analysis, field investigation at the source distribution, and the influence range of gas and hydrogen sulfide in coal seam in the affected range of the abandoned oil wells were studied. The results show that the coal-bearing strata in Shuang Ma coal field belong to the coal–oil coexistence strata, and the emission of H₂S gas in the local area of the working face is mainly affected by closed and abandoned oil wells. Within the influence range of the abandoned oil wells, along the direction of the working face, the concentration of CH₄ and H₂S gas in the borehole increases as you move closer to the coal center, and the two sides of the oil well show a decreasing trend. In the affected area of the abandoned oil well, the distribution of the desorption gas content in coal seam along the center distance of the oil well presents a decreasing trend in power function, particularly the closer the working face is to the center of the oil well. The higher the concentration of CH₄ and H₂S, the lower the concentration when the working face moves further away from the oil well. The influence radius of CH₄ and H₂S gas on the coal seam in the affected area of Ma tan 31 abandoned oil well is over 300 m. The results provide a theoretical basis for further understanding the law of gas and hydrogen sulfide enrichment in the mining face and the design of treatment measures within the influence range of abandoned oil wells.

A new algorithm is developed to fuse a high-resolution panchromatic (PAN) image and a low-resolution multispectral (MS) image based on wavelet transform. Firstly, this paper clarifies the concepts of and relationship between image fusion rule and operator based on wavelet transform; secondly, we propose a new strategy of calculating spatial frequency in accordance with wavelet decomposition characteristic. We adopt activity level comparison based on the spatial frequency to fuse the detail coefficient and weighted average method to fuse approximate image. Finally, this paper compares the fused results based on various wavelets, and presents objective and quantitative evaluation and analysis for the fused images

The effect of porous flexible polyvinyl chloride (PVC) barriers on the kinetic properties of propane explosions is investigated based on fluid dynamics and combustion-related theory. Furthermore, using small-sized cylindrical pipes, separate experimental studies on propane deflagration are conducted with different types of flexible PVC barriers placed in the pipeline. The results show that when the conditions of the same nature as the obstacles appear at the outlet end of the pipeline and the blocking rate is low, the presence of porous flexible PVC barriers counteracts the effect of tail-end barriers on propane deflagration. In the tail-end opening experiment, the porous flexible PVC obstacle has a significant effect on the flame pattern passing through it but has a weaker effect on the flames before they pass through it. Furthermore, it only affects the degree of “fingertip” sharpening of finger-shaped flames; the fewer the number of holes in the obstacle, the higher the sharpness of the fingertip flame. The porous flexible PVC barriers can reduce the rate of flame propagation and creasing of propane deflagration. The porous flexible PVC barriers have a lifting effect on the overpressure of the blast and a delaying effect on the onset of peak overpressure; the larger the number of holes in the barrier, the stronger the delaying effect.