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The instability and collapse of boreholes during coal seam gas extraction significantly affect the effectiveness of gas extraction. In response, this study selected human hair residue as the base material for composite protein foaming agents, leveraging the high protein content of animal hoof and hair materials to develop a high-strength, high-permeability, and environmentally friendly new type of foam concrete. This research found that the optimal ratio of foaming agent base solution to water is 1:4 when sodium hydroxide is used for protein hydrolysis. Comparing the foaming effects of sodium dodecyl sulfate (K12), α-sodium alpha-alkenyl sulfonate (AOS), sodium lauryl polyoxyethylene ether sulfate (SLS), and sodium dodecyl benzene sulfonate (LAS), sodium lauryl polyoxyethylene ether sulfate (SLS) exhibited the best foaming performance, while α-sodium alpha-alkenyl sulfonate (AOS) had the best foam stability. The optimal foam performance was achieved by mixing 2.0 g per liter of sodium lauryl polyoxyethylene ether sulfate and 0.3% calcium stearate. The experimental results showed that this foam concrete, with 25 mL of foaming agent, has a high strength exceeding 11 MPa and a high permeability with an average of 2.13 MD. This paper utilizes environmentally friendly materials and preparation processes. By using renewable resources such as human hair residue as raw materials, it helps reduce the dependence on natural resources and promotes sustainable development. This research demonstrates significant sustainability and provides the mining industry with an eco-friendly and efficient solution, with the potential to achieve positive economic and environmental benefits in practical applications. [ABSTRACT FROM AUTHOR]

Understanding the damage evolution behavior of coal under stress wave can provide a theoretical basis for preventing rock burst. In this work, the impact experiments of coal samples were carried out by split Hopkinson pressure bar (SHPB); the stress wave propagation characteristics were recorded by dynamic strain acquisition instrument; the evolution behaviors of coal samples’ surface displacement were analyzed by digital image correlation (DIC); the correlation between stress wave and displacement were discussed based on the multi-fractal theory. The results proved the stress wave propagates in the non-linear attenuation mode of multiple incidences, reflection, and transmission. Among them, the attenuation velocity of the incident wave is the largest, followed by the reflected wave, and the transmitted wave is the smallest. The incident and reflected stress waves are mainly dominated by high amplitude signals, while the transmitted stress waves are mainly dominated by low amplitude signals. The horizontal displacement on the coal sample surface is changed in the form of variable velocity, acceleration, and direction during the process of the stress wave propagation. The impact velocity is favorably linked with the amplitudes and attenuation velocities of incident, reflected, and transmitted waves as well as the surface displacement, displacement velocity, and acceleration of coal samples. The multi-fractal characteristic parameters of stress wave and displacement show that the proportional relationship and difference between the large- and small-scale displacement are influenced by those between the high- and low-intensity signal of the stress wave, and the transmission wave can exert greater influence. [ABSTRACT FROM AUTHOR]

As the coal mine gets deeper and the stopes' structures become more complex, gas and coal spontaneously burned composite disaster seriously threatens the efficient operation of coal mines. To study the interaction process and disaster-causing mechanism of gas and coal spontaneous combustion (GCSC), this paper establishes a numerical model to study the influence of drilling location/pressure and N2 injection on the evolution of gas and coal spontaneously burned composite disaster in the goaf. The simulation shows that in the central part of the goaf, a combined area of gas and coal combustion poses a possibility of spontaneous combustion calamity, and the length of the compound disaster area is about 20 m. The methane (CH4) explosion zone and the dioxygen(O2) temperature rise zone do not overlap in the air entrance roadway and return air roadway, indicating that there is no risk of compound disasters. The optimal nitrogen (N2) injection rate for this working face is 2000 m3/h, and the N2 port should be located 25 m profound into the goaf, which can effectively drive the diffusion of N2 and narrow the O2 zone's breadth. The findings have considerable engineering applications for revealing the evolution process, risk assessment and control for GCSC compound disasters in coal mines. [ABSTRACT FROM AUTHOR]