Coal gangue is a kind of industrial solid waste with serious ecological and environmental implications. Producing concrete with coal gangue aggregate is one of the green sustainable development requirements. This paper reviews the properties and preparation methods of Chinese gangue aggregate, studies the influence of gangue aggregate on concrete properties and the prediction model of gangue concrete, and summarizes the influence of modified materials on gangue concrete. The studies analyzed in this review show that different treatments influence the performance of coal gangue aggregate concrete. With the increase in the replacement ratio of coal gangue aggregate in concrete, the concrete workability and mechanical performance are reduced. Furthermore, the pore structure changes lead to decreased porosity, greatly affecting the durability. Coal gangue is not recommended for producing high-grade concretes. Nevertheless, pore structure can be improved by adding mineral admixtures, fibers, and admixtures to the coal gangue concrete. Hence, the working properties, mechanical properties, and durability of the concrete can be improved effectively, ensuring that coal gangue concrete meets engineering design requirements. Adding modified materials to coal gangue concrete is a viable future development direction.

To study the anisotropic mechanical characteristics of layered rock, typical phyllite specimens with bedding plane angles of 0°, 30°, 45°, and 90° were prepared, and triaxial loading and unloading tests under different confining pressures were conducted. Based on the experimental results, the anisotropic mechanical properties and fracture mechanisms of phyllite under different stress paths were analyzed. The results shown that under varying confining pressures, the elastic modulus and compressive strength of phyllite initially decreased and subsequently increased with the increase of bedding plane angle; With the increase in confining pressure, the compressive strength enhanced under both triaxial loading and unloading conditions; The failure modes of phyllite with different bedding plane angles exhibited significant anisotropy; While the residual friction angle exceeded the peak value in triaxial loading tests and showed the opposite trend in unloading tests, the residual cohesive strength remained consistently lower than the peak under different stress paths. Finally, a numerical model for simulating triaxial loading of phyllite was developed using PFC^2D. The numerical simulation results shown a high degree of consistency with the experimental findings, and the post-peak crack counts with different bedding plane angles were analyzed. The occurrence of the layered and matrix composite failure mode was closely associated with the strength ratio between the rock matrix and the bedding plane.

This study numerically investigated how varying pulse durations of water mist systems influence fire dynamics in long, narrow underground enclosures. A Fire Dynamics Simulator (FDS) model was built to represent a pulse-actuated, fine water mist test rig, and simulations of oil pan fires were performed to quantify the evolution of temperature and radiative heat flux. Results show that an 8 s spray followed by an 8 s pause yields the most effective suppression cycle. When spray and pause durations are equal, periodic momentum exchange resonates with the buoyant plume, intensifying the mixing of gas and enhancing cooling near the fire seat. Compared with continuous discharge, pulsed mist generates stronger buoyancy-driven disturbances and delivers superior performance in terms of local heat’s extraction and extinguishment. This study has, for the first time, determined the optimal pulse cycle (8 s spray/8 s stop) for oil pool fires in narrow and long underground spaces through FDS simulation, and revealed the enhancement effect of the gas disturbance resonance mechanism on fire suppression efficiency.