Due to their complex geological structure, it is difficult to systematically analyze the surface subsidence of coal mines in southwest China, and the factors that cause surface subsidence are also different from other coal mines. Focusing on the problem of surface subsidence caused by mining in southwest China’s mines, a grade evaluation system for surface subsidence of southwest mines is constructed based on the analytic hierarchy process, and ten evaluation indicators are established from the perspectives of mining disturbance and geological structure. A matter–element model of surface subsidence based on matter–element extension theory and a cloud model of surface subsidence based on cloud theory are then constructed. A coal mine in Anshun, Guizhou, is taken as an example to calculate the evaluation level of surface subsidence and thus verify the scientificity of extension theory and cloud theory. The results show that the main factors that affect the surface subsidence of southwest mines are the number of coal seam layers, mining height and comprehensive Platt hardness of rock, similar to that of northern plain coal mines. Surface slope and subsidence area are also very important. The comprehensive correlation degree of each grade of the coal mine is −0.29836, 0.192232, −0.1093 and −0.46531, and the coal mine is concluded to be in grade 2. The calculated similarity of the overall index evaluation cloud map of the coal mine and each grade is 0, 0.3453, 0.7872 and 0, respectively. The coal mine is in grade 2, which is a relatively safe state. Consistent with the calculation results of the extension model and in line with the field situation, the extension matter–element model and cloud model built in this paper can verify each other and have a certain scientificity.

In this paper, to reflect a real fire combustion situation of stilted buildings with a typical wooden structure, we used FDS numerical simulation software to study the suppression effect of a fine-water-mist fire-extinguishing system under different working conditions. The influences of different mist droplet diameters, spray flows, and nozzle densities on the temperature change in the combustion area were analyzed and compared. The particle sizes of fog droplets exhibited a significant impact, indicating that the smaller the particle size, the faster the vaporization rate and the better the cooling effect. The cooling effect was better when the particle size was 150 μm or less when compared to the particle sizes of 200 and 300 μm. As the spray flow rate and nozzle density were increased, the fire field temperature decreased, and the cooling effect was enhanced, optimal at a water-mist flow rate of 8 L/min. Therefore, given the possible working conditions, the spray flow rate and the nozzle density should be high, while a suitable droplet size should be selected to achieve the best fire-extinguishing effect.