Study On Outburst Prevention Mechanism And Injection Parameters Optimization Of Hydraulic Extrusion

Hydraulic extrusion is a new developing measure against coal and gas outburst in recent years, safe and rapid driving can be implied by this measure in coal bed with outburst potential. The actual results of applying in some mines show that the quantities of construction work are few, construction work is safe, the effective of outburst prevention is significant, the rate of exceeding standard value of validity checking is low, the environment of working face is also improved obviously. But, the mechanism of outburst control is not realized deeply, water injection parameter is not chosen sensibly. In this paper, commercial test of the field, laboratory experiment and theory analyses are used to analyze the procedure of hydraulic extrusion measure. The technology system and equipment of hydraulic extrusion are set forth, based on coal and gas outburst mechanism, and associated with abundant investigations of outburst prevention result; mechanism of outburst prevention of hydraulic extrusion measure is analyzed, then, by the method of experimental simulation, the action mechanism of gas extraction influenced by high pressure water, it perfect the mechanism of outburst prevention of hydraulic extrusion measure. The in-suit experimental results shows that, while adopting the measure of hydraulic extrusion at outburst coal seam, stress concentration region of working face is moved to the depth of coal seam, pressure relief region is widened, and stress concentration degree of upper coal wall is released sufficiently, so, the region of outburst prevention is enlarged. Because coal seams is fractured and loosen by high pressure, gas permeability of coal seam is also enhanced when adopting hydraulic extrusion; free gas contained in the coal seam is released sufficiently, so, gas content and pressure is reduced. High pressure has the effect of blocking gas after adopting hydraulic extrusion, then, adsorbed gas is released hardly, so, the gas extraction velocity is reduced and gas emission is also reduced. When coal is humidified by high pressure water, physical and mechanical quality of the coal is changed, and its plastic nature is enhanced, on the contrary, its elastic nature is descended. At last, with the mathematical method of the theory of quantification I and orthogonal test design, and according to the practical water injection parameter in the field and the investigation of water injection result, the optimum unit of water injection parameter is deduced, and water injection parameter of hydraulic extrusion is optimized, it is complied with the actual condition in the field. By the theoretical analysis and commercial test, hydraulic extrusion measure is demonstrated to have extensive adaptability, availability and security to rapid excavation in seam gateway with outburst potential.