Theoretical and experimental studies on drilling cutting weight considering effective stress

Considering that the horizontal stress can not be ignored under deep mining, the new formula for drilling cutting weight is derived based on the effective stress. The relationship between the effective stress and the drilling cutting weight is analyzed. The method for judging the drilling cutting weight by the effective stress is put forward. On this basis, by taking the typical high gassy mine of Sunjiawan Coal Mine in Fuxin as an example, using the developed 3D stress test devices for coal drilling cutting weight and changing the axial pressure to simulate the vertical crustal stress, the confining pressure is used to simulate the vertical crustal stress and the pore pressure is used to simulate the gas pressure. Laboratory experiments are carried out to study the effects of the effective stress, coal seam depth and gas pressure on the drilling cutting weight. The results show that the drilling cutting weight increases linearly with the effective stress, and the test values are slightly larger than the theoretical ones, and the average error deviation is 7.9%, which is consistent with the previous conclusions. This verifies the reliability of the new formula for drilling cutting weight and the three-dimensional stress test devices. With the increasing depths, the drilling cutting weight is greater, that is to say, the drilling cutting weight increases linearly with the depth of coal seam. With the increase of drilling depth, the drilling cutting weight firstly decreases and then increases and finally decreases slowly. The location of the maximum amount of drilling cuttings is at the depth of 12.5 cm, which indicates that the place is the stress concentration area. With the increase of gas pressure, the drilling cutting weight increases in the form of exponential function, and it has a significant influence on the shape of the coal wall and the hole. With the increase of gas pressure, the more obvious the crack growth of the hole wall, the more remarkable the softening effect of the coal seam. The conclusions have an important reference value for the prediction and control of coal and gas outburst in coal mines.