Law and mechanism of subsidence reduction of grouting in mining goaf area

Similar material simulation experiments on grouting in the goaf, aiming to investigate the damage characteristics of the overburden and the movement behavior both before and after grouting were conducted. The results demonstrate that after grouting the goaf, large fissures, fractures, holes, and other cavities are effectively sealed by the slurry. Compared to untreated goaf, grouting significantly reduces subsidence, with a reduction rate of up to 92.3%. The slurry grouting compacts the residual voids in the goaf, slowing the further subsidence of the collapsed area. It also provides lateral support and a barrier to water infiltration in the residual coal pillars. Additionally, the slurry improves the stress conditions of these coal pillars, transforming the initial unidirectional (or bidirectional) stress state into a bidirectional (or triaxial) stress state. This significantly enhances the support strength and stability of the coal pillars.