Based on thermal–fluid–solid coupling law in coal and gas outburst, a multi-physical field numerical analysis model is built for the whole outburst process. The response laws of stress, gas pressure, temperature, and seepage in different areas and different time nodes around coal and rock mass in the coal and gas outburst under high stress condition are discussed. Research results show: Firstly, the stress response law of the coal and rock mass around the burst hole is initial vibration–sudden attenuation–late stability. Secondly, the gas pressure response law in different areas is that the gas pressure response rate decreases gradually with the increase of the distance from the outburst. Thirdly, the adsorbed gas contained in the broken coal near the outburst port is desorbed rapidly and expands to do work, and the temperature changes dramatically after outburst occurs. In contrast, with the increase of stress, the proportion of elastic potential in total coal and gas outburst energy increases, and the proportion of elastic potential is positively correlated with stress. The critical gas pressure under the energy condition of coal and gas outburst decreases with the increase of stress. It illustrates that the lower gas pressure can also meet the energy condition of coal and gas outburst under high stress.

This study comprehensively combines physical analog modeling, numerical simulation, on-site monitoring, and other methods to explore the overburden rock fissure development characteristics under double-roof-cutting (DRC) with retained roadway conditions. The analysis of performed tests, simulations, and on-site monitoring proves that under the above mining conditions, the stress transfer between the roof plates of the open area and the roadway on both sides of the cut top is interrupted, the overburden load being retained in the middle of the open area. The stress in the middle of the open area of the former is increased by 5% compared with that of the latter, with a higher degree of stress increase. The amount of overburden rock subsidence in the open area of the former is reduced by 45–80% compared with the latter. Under DRC, heights of the overlying rock collapse and fissure zones are 18 m and 40 m, respectively, versus 15 m and 46 m of those without roof-cutting. Fissures in both zones are the most developed, turning into gas transportation channels. This study findings provide theoretical basis for exploring the gas transportation patterns in double-cutting top tunnels.

The behavior of gas migration in goaf under double roof cutting conditions directly influences the effectiveness of gas control measures. This study employs a combination of numerical simulation and field verification to investigate the patterns of gas migration and accumulation in goaf and to develop coordinated gas control methods under the conditions of double roof cutting and retained roadway. The results indicate that with double roof cutting, goaf permeability generally increases from the interior towards the exterior, with significantly higher porosity in the separation range compared to other areas. High permeability channels form along the sides of the open-off cut, the working face, and the two roadways, subsequently becoming areas of gas accumulation. High-level directional long borehole drainage achieves the best gas drainage at the bottom of the goaf on the working face and belt roadway sides, reducing gas concentration in the working face space to below 0.5%. Pipe jacking extraction along the retained roadway effectively reduces gas concentrations on the working face side and both roadway sides, maintaining working face gas concentrations consistently below 0.3%. Supplementary cutting hole drilling and extraction post-goaf formation show optimal gas extraction results on the working face side and near the two roadways, with gas concentration in the upper corner and return airflow remaining below 0.3% and trending downward. Field data validate the numerical simulation experiment theory.

Double-cutting top-retention mining is one of the important directions for sustainable coal development, and its mining-induced overburden fissure evolution law determines the response of unloading gas extraction projects. This paper used physical analog modeling experiments to compare and analyze the overburden fissure evolution laws induced by double-roof-cutting and conventional mining methods. The results show that double-cutting roof alley mining has a significant controlling effect on roof decompression, settlement, and fissure development, and the basic roof subsidence of the interlayer after cutting the roof is small, with the maximum subsidence of 9.85 mm; the rock layer after the roof collapse in conventional mining is more fragmented, and the range of fissure development is larger than that in double-roof-cutting with retained roadway conditions, having the maximum subsidence of 13.65 mm. The latter achieves a more uniform overall settlement by decompressing the roof and making the angle of collapse, fissure development height, and width smaller than under conventional mining. The double-roof-cutting mining reduces the degree of stress concentration in the surrounding rock, promotes the settlement of the roof and the time of the first pressure, improves the stability of the roadway, and forms an effective gas transport channel through the roof slit.

Deep coal seams have low permeability and poor wettability, making gas extraction difficult. This study presents a zero-energy consumption pulsating water hammer fracturing technique that uses the gravitational potential energy of high-elevation water and the pulsating pressure waves from the water hammer effect to induce fatigue damage in coal, creating an interconnected network of cracks. The research included experiments on water hammer pressure waves, multi-physics field coupling simulations at different flow rates, and discrete element simulations to analyze the fracture behavior of underwater hammer pressure. Results showed that initial flow velocity impacts the water hammer pressure’s intensity, range, and duration. Pressure shock waves propagate as expansion and compression waves, with peaks rising from 4.99 to 19.91 MPa within a 2–12 m/s flow rate range. Water hammer pressure reduced fracture initiation pressure by 23% compared to static pressure loading and increased fracture numbers by 13.4%. With pressure amplitudes between 2–18 MPa, fractures tripled, and the damaged area grew from 2.2 to 11%. A variable frequency combination loading strategy, starting with low frequency and then high frequency, was more effective for fracture propagation. This study offers a theoretical foundation for applying this technology to enhance coal seam permeability and gas pumping efficiency.