Study on drilling mechanism of combined bit in hard coal seam

• Published in: Journal of physics. Conference series 2020-06, Vol.1549 (4), p.42138
• Main Authors: Li, Yan, Shi, Wenbao
• Format: Article
• Language: English
• Subjects: Boreholes; Breaking; Coal; Drill bits; Drilling; Drills; Geology; Mathematical models; Rock masses
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/1549/4/042138

Borehole pressure relief can effectively reduce the accumulation of elastic energy of working face and surrounding rock mass, and reduce the regional impact risk. But in hard coal seam, drilling jam, holding and other dynamic phenomena often occur in drilling, which seriously reduces drilling efficiency. Therefore, aiming at the problem of poor coal breaking effect of traditional geological drills in hard coal and rock, the coal breaking characteristics of new type combined drills are studied by theoretical analysis and numerical simulation. Considering the traction, rotation and impact movement in practical work, the trajectory model of combined drills is put forward. The coal breaking characteristics of the two kinds of drills are compared and analysed from the aspects of the difficulty of coal breaking and the force fluctuation of the drill bit. The results show that the combined bit can reduce the difficulty of coal breaking by 50% when its hardness value is twin 6, and the combined bit can reduce the force of nearly 7000N in hard coal and rock in the fluctuation of force acting on the geological bit. Therefore, the study of coal breaking characteristics of the combined bit can effectively improve the special rock mass such as broken hard coal and rock.