Research and Application of the Deviation Reduction Mechanism in Stratified Cutting Drilling of Soft-Fragmented Coal Seams

In order to solve the problem of drilling deflection, the method of cutting drilling by layers is proposed. The mathematical model of the force of the layered cutting bit was established, and the influencing factors of bit deflection were obtained. The stress equation of the cutting bit is constructed, and the ABAQUS numerical model is established. The influencing factors of the deflection of the bit are analyzed. A comparative industrial test was carried out in the Tunlan Mine. The analysis results show that the main influencing factors of bit deflection are the tangential force on bit f w , the axial force on bit f t , the length of the straightener rod l, the elastic modulus of the surrounding rock E, the length of the straightener bit and reaming bit h, and the diameter of the drilling hole D. When the axial force on the bit is between 120 and 220 KN, the change of axial force has almost no effect on the deviation angle of the drill hole. The change of f w and l is linearly negatively correlated with the bit deviation angle between 50 and 300 mm. Compared with the conventional drill, the horizontal deviation and vertical deviation of the layered cutting bit are reduced by 23% and 43% on average, respectively.