Analysis of orifice pressure and material selection in the process of grouting of overburden separated layer

Overburden separation grouting is an effective technical method for controlling surface subsidence in coal mining. To investigate the dynamic evolution of orifice pressure during construction and the rational selection of grouting materials, this study analyzes the effects of geological conditions and grouting processes on orifice pressure, and establishes an orifice pressure calculation model and a pressure regulation system based on feedback control principles. Furthermore, through performance analysis of grouting materials and based on the basic principles of material selection, an optimized mix proportion scheme for suitable grouting materials is selected. The experimental results show that under high-pressure grouting conditions, the single-pipe grouting method is prone to local stress concentration and fatigue failure of the pipeline. By optimizing a cement–fly ash–sodium silicate (water glass) composite grouting material, when the mass ratio of cement to fly ash is 1:2 and the sodium silicate content is 3%–5%, the slurry exhibits good fluidity and high early strength. The research results provide a theoretical basis for pressure control and material selection in overburden separation grouting construction, and provide solid technical and theoretical support for improving grouting effectiveness, controlling surface subsidence, and promoting green mining.