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Based on the industrial application of fly ash, a new method of using fly ash instead of sand as the main raw material for wall grouting of coal mine roadway is proposed. The effect of fly ash instead of sand on the compressive strength of shotcrete was studied, and the activation of fly ash shotcrete with Na2SO4, NaOH and Na2SiO3 were studied. The results show that the compressive strength of the grouting material is lower than that of the traditional grouting material when the fly ash completely replaces the sand, which can not meet the requirement of field application, the problem of compressive strength of fly ash shotcrete can be effectively solved by adding proper amount of alkaline activator, and when the content of Na2SO4 is 3%, the increase of compressive strength of fly ash shotcrete is the best.

In order to reveal the law of repeated mining of shallow coal seams under the peak cluster landform, the overlying strata fracture migration and peak cluster movement deformation laws induced by the mining face, Taking Guizhou typical peak cluster landform as the engineering background, with the help of similar simulation, UDEC numerical simulation and theoretical analysis, the overlying rock movement and surface movement and evolution law of working face are studied. The results showed that with the mining of coal seams, cracks appeared on the left and right sides of the mountain slope. As the working face advances, the cracks gradually shrink. Repeated mining has less damage to the rock mass structure on the left and right sides of the peak, but more serious damage to the internal rock mass structure. After the coal seam is mined, the UDEC model is used to analyze the development of the vertical stress and vertical displacement of the peak body. It is found that the vertical stress is mainly concentrated in the central part of the peak body, and the area with larger vertical displacement value is also the central part of the peak body. At the same time, after the coal seam mining is over, both the similar simulation model and the UDEC model have a certain degree of subsidence, and the area with the largest subsidence is the peak part of the peak cluster.