Weight analysis and experimental study on influencing factors of high-voltage electro-pulse boring

Abstract

Electro-pulse boring (EPB) has the advantages of high rock-breaking efficiency and good borehole wall quality, which is a new type of rock-breaking method with potential and close to industrialization. EPB is affected by many factors, such as voltage, electrode structure shape, rock composition, discharge times and so on. Firstly, according to the established simulation model of EPB and the previous research on electric breakdown model of rock, the maximum electric field strength in rock, the electric breakdown field strength of rock and its ratio with different influencing factors were simulated and calculated. Secondly, the probability of electric breakdown with different influencing factors was obtained. The extreme learning machine and average influence value (ELM-MIV) algorithm was proposed to analyze the weight of the six influencing factors on the probability of electric breakdown, such as peak voltage, electrode spacing, electrode angle, and so on. The correlation and contribution degree of the influencing factors on the electric breakdown probability were obtained. Then, the EPB experiment system based on the transformer-type pulse power supply was developed, and the coaxial cylindrical electrode bits with the spacing of 25 mm and 45 mm were developed. The drilling diameter of red sandstone was 100 mm and 60 mm, respectively. The results showed that the energy consumption of EPB was about 100–300 J/cm3 without slag discharge system. Finally, the influence experiments on EPB were carried out, and the influence rules of electrode spacing, discharge times and rock composition on EPB were obtained. It provided guidance and basis for the design of electrode bit and the selection of drilling technology parameters in different strata through the research on the influencing laws of EPB. It was of great significance to improve the efficiency and reduce the energy loss in the process of EPB.