The Numerical Research on Rock Breaking and Rising Mechanism of Rotary-Percussive Drilling

In this paper, the numerical simulation is used to study the rising mechanism of rotary-percussive drilling, which is under the combination of rotary cutting and axial impact. The main objective of the present work is to compare and investigate the breaking process of rock element and the motion state of drilling bit under the conventional drilling and rotary punching drilling. Additionally, the single-factor analysis is used to analyze the effects of impulse load, impulse frequency, rotary speed and formation hardness on rock breaking efficiency and acceleration effect of rotary percussion drilling. Through the investigation, it is found that there are more areas of tension stress breakage in rock elements under rotary-percussive drilling. Rotary percussion drilling can effectively alleviate the stick–slip vibration of drilling bit. At the same time, the relationship between the average penetration rate of the bit and the impulse load, impulse frequency, rotary speed and formation hardness is shown. The results of the study will be beneficial to provide some theoretical reference for the development of tools and the selection of working parameters of rotary-percussive drilling technology, as well as for the drilling methods of deep wells and hard rocks.