Experimental study on void evolution and slurry diffusion mechanism of fractured rock body in collapsed zone

In order to reveal the compaction and deformation mechanism of the crushed rock body in the collapse zone of the hollow area and the rule of slurry diffusion, the rock body in the collapse zone of the 10806 integrated mining face was taken as the object of the study, and indoor physical simulation and ANSYS Fluent numerical simulation were combined to carry out the study. Firstly, a multi-axial loading platform was used to carry out the compaction test of the broken rock body, and the rock body was graded according to the grain sizes of 0–2, 2–4, 4–6, 6–8 and 8-10cm to analyze the compression deformation and void evolution characteristics; then a visual grouting system was used to study the flow pattern of the slurry; finally, models with different porosities (0.4, 0.6) were constructed to investigate the effect of grouting pressure (10 kPa-1 MPa) on the diffusion of the slurry. Finally, different porosity (0.4, 0.6) models were constructed to investigate the effect of grouting pressure (10kPa ~ 1MPa) on slurry diffusion. The results show that: the compression of fractured rock body is divided into two stages: rapid (74%-85.7% of total deformation) and slowing down, and the rapid compression stage is the optimal time for filling; the smaller the porosity is, the slower the flow rate of the slurry, and the lower the filling efficiency is; the positive correlation between grouting pressure and slurry diffusion area and flow rate, and the best filling effect is achieved when 1MPa is used, and the compacted area needs higher pressure and encrypted grouting holes. The study can provide theoretical basis for the optimization of filling parameters in the collapse zone of the hollow zone.