Experimental Study On The Flow Law Of Slurry Of Isolated Grouting In Mining-induced Overburden

The flow law of grout in overburden mining-induced fractures is an important theoretical basis for grouting and filling design.The core problem of grouting filling is determined by analyzing the grouting flow under the condition of overburden isolation grouting.Guided by the grouting pressure,the flow law of fly ash slurry was divided into two stages: "no pressure" and "with pressure".By designing a visualization grouting filling slurry flow simulation experimental system in overburden,the experimental study on the flow law of fly ash slurry in the no-pressure stage and pressure-free stage was carried out.In this paper,the flow law of the overburden isolation grouting filling slurry in the no-pressure stage is studied by combining theoretical analysis with experimental study.The dimensionless formula of slurry flow distance was established by dimensional analysis method.The dimensionless equation is solved based on the experimental results of grouting filling slurry flow simulation.The effects of the grouting flow rate,the height of the final hole from the bottom of the fissure,the viscosity of the slurry on the flow distance of fly ash slurry and the morphology of the slurry were studied.The results show that in the no-pressure stage,the slurry flow goes through two stages: radial flow and two-way flow,and two-way flow is the main flow.In the radial stage,the flow is circular with the grouting hole as the center,while in the bidirectional stage,the flow is symmetrical on both sides.Based on the experimental results,the flow distance formula of the slurry in the no-pressure stage was solved,and the validity of the formula was verified.In order to simulate the flow process of the slurry from no pressure to pressure in the separation stage,a simulation experimental system of the slurry flow in the isolation grouting of mining-induced overburden was designed.The flow channel of the slurry,the pressure distribution in the separation cavity,the consolidation of the slurry and the thickness distribution of the backfill were studied by using the experimental system.The results show that after entering the pressure-free stage,the slurry flow field begins to present an approximately elliptical dominant flow channel,which expands along the direction and the flatness increases continuously.The grouting pressure increases with the increase of grouting time,and the pressure at each point shows a similar trend,and the pressure value shows slight difference,and the grouting pressure at the point farther away from the borehole has a slight attenuation.The thickness of the slurry is larger in the middle and smaller on both sides of the ladder.The research results clarify the law of grout flow and provide a theoretical basis for the design of overburden isolation grouting filling.This paper contains 29 pictures,3 tables and 140 references.