Experimental study on high-pressure hydraulic percussive rotary drilling based on single-tooth rock-breaking process

Aiming at the problem of low efficiency of hard rock drilling in crossing borehole in underground coal mine, the morphology of crushing pit formed by column tooth under the percussive load was analyzed based on the percussive rotary drilling mechanism and the main characteristics of Wassara high-pressure hydraulic impactor, and the crushing pit was divided into the four areas of disintegration area, compact area, crack area and elastic area. On this basis, process analysis was performed on the continuous tooth rock-breaking with large and small interval impact. Meanwhile, the technical parameters of high-pressure hydraulic percussive rotary drilling were discussed with reference to the field test conditions of Huainan Pansan Mine. The drilling rig, impactor, drill pipe, drill bit and clean water pump for high-pressure hydraulic percussive rotary drilling were selected preferably, for which the main technical parameters were given. The test results show that the average rate of penetration of high-pressure hydraulic percussive rotary drilling is 24.67 m/h at the clean water pressure above 15 MPa, which is about 1.9 times higher than that of 8.48 m/h without adopting this technology. Besides, the linear relationship between the rate of penetration and water pressure is obtained by regression analysis fitting. According to the F-test of mathematical statistics, the regression results are verified to be significant with F=8.82>F_0.05(1,7) and the correlation coefficient, and the rate of penetration increases linearly with the increase of water pressure. Generally, the high-pressure hydraulic percussive rotary drilling technology could effectively improve the drilling efficiency of hard rock borehole in underground coal mine and ensure the safe and efficient production of coal mine.