Mining-induced off-layer space evolution law and gangue grouting filling control mechanism

Separation grouting filling technology is widely used in surface subsidence management because of its simple process and good overburden control effect, while the changing pattern of overburden off-layer space (OS) during the mining process plays a key role in the selection of grouting timing and rock control effect. In this paper, the law of OS development and the mechanism of rock movement control by gangue slurry filling is studied by combining numerical simulation and physically similar simulation experiments with the engineering background of the 3⁻¹801 working face of Hongqinghe coal mine. The results of the study indicate that the OS undergoes a slow growth period, an accelerated expansion period, a slow decrease period, and an accelerated decay period during the development process. The change of OS is closely related to the form of key layer bending and sinking, and the change of key layer from V-type sinking to basin-type sinking during the mining process is the turning point when the OS starts to decay faster, and timely grouting and filling before the turning point can effectively control the key layer breaking and sinking, reduce the stress concentration, and the effect of rock layer sinking reduction is obvious. The research results of this paper have certain theoretical value and practical significance for the technical scheme design of OS grouting and gangue filling treatment.