Experimental Study Of Pressure And Strain Distribution Around Hydraulic Borehole

For controlling the coal and gas outburst of coal seam with low gas permeability in our country, we often use hydraulic drillings to unload the pressure and increase seam permeability. Although the application of such measures in the field has achieved good results, specific selection of hydraulic drilling parameters is still lack of in-depth study. For the problems of the drilling measures in this stage, this paper built a corresponding experimental system in the laboratory to determine parameters combined with numerical simulation and to study the pressure and strain distribution around hydraulic borehole. In this way,we can provide a theoretical basis for the selection of coal mine hydraulic drilling parameters. Besides, we also carry out the relevant tests in the coal mine. According to test "Coal and Gas Outburst Prevention Regulations ", the resulting law was confirmed in the laboratory. Specific research contents and results are as follows.(1) We build a experimental system to study the pressure and strain distribution around hydraulic borehole, this system can meet experimental feature and measure the moisture content of the coal seam in different stress, water pore size and water pressure.(2) Studied the hydraulic drilling of radial stress distribution and the water content in the help of our system. It confirms the effect of pressure relief in hydraulic borehole which contrast to stress distribution of ordinary borehole.(3) On the basis of drilling radial distribution of moisture, we established a model of pressure and strain distribution around hydraulic drill which used the parameters of Linhuan coal mine. And carried out experimental simulations in different stress, water aperture and water pressure, etc. In the end, we got the pressure and strain distribution around hydraulic borehole.(4) Tested two different aperture Φ200mm and Φ600mm hydraulic coal drilling and obtain radial movement deformation law of hydraulic borehole, and determine the specific relief drilling range in the expansion deformation of indicators. Finally the test results show that the effective relief radius of Φ600mm hydraulic coal drilling increases 1.71 m than Φ200mm hydraulic coal drilling.