Abstract
High-voltage electro pulse boring (EPB) has the advantages of high rock-breaking efficiency and good wall quality, and is a new and efficient potential method of rock breaking. The EPB process is defined as random because it is affected by many factors. At present, there is no suitable physical and mathematical model to describe the process and results of rock breakage in EPB, and the conclusions reached regarding rock-breakage mechanisms are not uniform. In this study, a complete damage model of high voltage EPB in granite is established, which includes a shock wave model and a damage model of high voltage EPB in granite. The damage model is based on the Particle Flow Code two-dimensional program. Use of a damage model of EPB accommodates the complete process of high voltage EPB, from discharge to production of a shock wave, and so rock-breaking via electro pulse can be simulated and calculated. The time-varying waveforms of shock waves with different electrical parameters are simulated and calculated on the basis of the model. Different shock wave forms are loaded into the surface and internal rock in the damage geometric model of EPB granite. Then, the breakage process of the rock surface and internally, and the mechanism of rock breakage using EPB are analyzed. This study provides a scientific basis for the quantitative expression and prediction of rock fragmentation in EPB in order to improve the drilling efficiency and reduction of energy loss in the process of EPB.
Highlights
The drilling depth of oil, natural gas, and geothermal wells is increasing [1]
In research on a mechanical model of rock breaking using a high voltage electro pulse, Cho et al [7] found that the fracture model of rock is like that of the quasi-static, multi-crack model derived from computed tomography (CT) scanning under the action of a short electric pulse
Plasma channel radius, r, and shock wave pressure, P, which vary with time under different electrical parameters, can Model be obtained
Summary
The drilling depth of oil, natural gas, and geothermal wells is increasing [1]. Traditional mechanical drilling has the disadvantages of low drilling efficiency, high drilling cost, and large bit wear in the processes of deep drilling, ultra-deep drilling, and hard rock drilling. The construction methods of rapid excavation and tunneling in medium-hard rock and hard rock, such as drilling and blasting method and full-face hard rock tunneling, have shortcomings, such as high consumption costs and stricter requirements on geological conditions [2] It is, an imperative to study high-efficiency rock-breaking drilling technology. A complete damage model of high-voltage EPB in granite is established in this study. The fracture process and mechanism of high voltage EPB in surface and in the internal mesoscopic medium of granite are revealed under the multi-physics fields of electric field, temperature field, displacement field, and flow field in Sections 5.2 and 5.3.
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