Study On The Hydraulic Flushing Borehole In The Coal Seams Of Mine Influence

Because China’s coal geology condition are complicated, existed condition complicated, gas outburst is extremely serious, and the number of occurrence is more, the number of gas emission is also great, the event of a gas explosion will cause a great loss of human and financial resources.Coal seam gas pre-pumping rate increase is a strong measure to combat the the powerful coal and gas outburst in one of the measures.The pre-drainage can reduce the counter of gas and gas pressure in the dust.The hydraulic flushing is to flush out the different diameters holes in the coal by the1. Along with the swelling deformation of the coal mass, the permeability of the coal mass increase.In this paper,the combined methods of theoretical analysis, numerical simulation and field testing are used. This paper primary researches the distribution of stress, the development of the fracture and the change law of the permeability in the coal mass after hydraulic punching. The research results is applied in gas control in No.6coal of Zhangji coal mine. And the researches has important guiding significance for the gas control of the other coal seam with the similar gas occurrence.On the theoretical side, analysis of the change of the permeability in the coal seam by solid-liquid coupling theory.In this thesis, simulates and forecasts the results of experiments by RFPA2D-Flow.Discussion of the distribution of stress in coal body around boreholes after hydraulic flushing by numerical simulation methods.The stresses distribution region is divided into three zones. The hydraulic flushing technology is to flush out some diameter holes in outburst coal seam by using high-pressure water jet technology. In the process of hydraulic flushing, along with the hole diameter enlarge,the peak of the stress concentration continuously moved to the depths of the coal body,and the effective range of hydraulic flushing is unceasingly expanding.The numerical simulation result shows that the effective influencing radius of hydraulic flushing is5m-10m. The Zhangbei mine was selected as the test field.The effective hydraulic pressure is10MPa-15MPa. Based on the test results,the effective influencing radius of hydraulic flushing is7.5m-10m. And numerical simulation result basically coincides with experiment measuring result. Overall,hydraulic flushing has great influence on the distribution of the stress and gas in the coal seam. Though theoretical analysis, laboratory studies and field test, it is proved that hydraulic flushing have broad applicability and effectiveness for the outburst prevention in high gas outburst coal seam.