Study On Slag Discharge Mechanism And Optimization Of Rib Drill Pipe For Mine

Gas outburst has always been a major safety problem threatening the coal mine production,especially in the mining process of soft outburst coal seams.At present,using the rib drill rod to drill a holes in specific areas of coal wall for draining gas is a commonly method to solve the problem of gas outburst.Due to the limitation of existing slag discharge technology,sticking accidents often occur and lead to very low drilling depth and porosity,thus greatly reducing the efficiency and effect of gas control.In order to solve the above problems,this paper studies the slag discharge mechanism of the rib drill pipe,and puts forward the drill pipe optimization scheme.Aiming at the complex working conditions of drilling in soft and outburst coal seam,the comprehensive research methods of borehole theoretical analysis,slag discharge numerical simulation and laboratory experiments are adopted to carry out in-depth study on slag discharge mechanism of rib drill pipe.The mechanical model of coal slag in the process of slag discharge is established,and the calculation formulas of the slag discharge rate per unit time of fluid and mechanical slag discharge are deduced,and the influencing factors of the optimized slag discharge efficiency are found out.Based on the slag discharging technology in borehole construction,the slag discharging process is simulated as a gas-solid two-phase flow coupling process by using computational fluid dynamics theory.Two special numerical simulation tools,EDEM and FLUENT,are used to establish a gas-solid coupling model for the slag discharging in drilling.The parameters to be optimized for the rib drill pipe are obtained by setting up the parameters to simulate the actual drilling conditions.Based on the results of coupled numerical simulation,25 models were designed by orthogonal experiCent L25(55 orthogonal table,and the parameters of rib drill pipe were optimized.The optimal combination of parameters was obtained by range analysis method.Based on the optimal combination of drill pipe parameters,the shape of drill pipe blade is optimized.The optimization results show that the slag discharge efficiency is increased by 15.77%.Based on the actual working conditions of drilling construction,a special test bench for slag discharge from rib drill pipe was designed and built.According to the results of coupled numerical simulation and optimization,a new structure ribbed drill pipe was manufactured,and 15 simulated slag removal experiments were carried out on each drill pipe,and the residual coal slag quality in the slag removal channel was counted.The experimental results show that the new structure rib drill pipe is 9.40%of the original rib drill pipe,and the accumulation rate of slag decreases significantly,which greatly reduces the possibility of sticking due to slag blockage.