Research on grouting subsidence reduction technology of overburden separation layer in isolated working face mining under village

There is a large amount of coal under village buildings in China. It is of great significance to study the mining of coal under villages to improve the recovery rate of coal resources and alleviate the contradiction between mining and excavation. Theoretical analysis, engineering test, field monitoring and other methods are used to study the separation grouting and subsidence reduction technology of soft and hard rock interbedded overburden in island working face under village. Through the analysis of the overlying rock mechanics theory of soft and hard rock interbedded strata, the development characteristics of overburden separation after coal seam mining under the condition of soft and hard rock interbedded strata are obtained, and a multi-layer separation grouting and subsidence reduction technology is proposed. At the same time, a ‘three-step’ curtain-separation grouting technology for overburden and goaf was developed and implemented. According to the analysis of the characteristics of multi-layer separation grouting technology, the principle and advantages of multi-layer separation grouting, the thickness and stability of protective layer, grouting pressure and slurry permeability, multi-layer separation space volume and filling amount are discussed. The field test and monitoring show that the surface subsidence coefficient is reduced to 0.15–0.17 after the separation grouting technology is adopted, and the surface subsidence reduction rate is 75.8%–79.3%. The research effectively protects the surface buildings, realizes the village not to move coal mining, and provides an important reference for the subsidence reduction technology of the separation grouting project under the buildings and structures.