Damage Model and Numerical Experiment of High-Voltage Electro Pulse Boring in Granite

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.

An Electro Breakdown Damage Model for Granite and Simulation of Deep Drilling by High‐Voltage Electropulse Boring

“…Model by High-Voltage Electro-Pulse e EPB process can be divided into three phases: (1) electro-breakdown, (2) energy injection into the plasma channel, and (3) shock-wave fracturing [32,33]. ese phases can be simulated by a high-voltage electro-pulse breakdown model, shock wave model, and numerical simulation model, respectively.…”

“…In an electrostatic field environment, the breakdown type of rock is electro-breakdown. According to the theory whereby breakdown occurs at weak points [32], the breakdown of solid dielectrics begins at weak points such as cracks or holes. e Kratal cylindrical channel model was used as the plasma channel model of electro breakdown in this paper [33].…”

“…Considering granite as the fragmentation object, the electrical impedance of granite extends from the electrical insulation to the breakdown point at which the plasma channel is generated and it has a functional relationship with the discharge time and current. e plasma channel impedance model used here adopts the Weizel-Rompe model [32], and the impedance can be expressed in the form of a current integral, as follows:…”

Simulating Plasma Formation in Pores under Short Electric Pulses for Plasma Pulse Geo Drilling (PPGD)

“…Plasma Pulse Geo Drilling (PPGD) is a novel contactless drilling technology, which uses high-voltage electric pulses to break away the rock, without relying on mechanical abrasion (e.g., [5,[8][9][10][11][12][13][14][15][16][17][18][19]). Thus, PPGD is part of a class of new "contactless" drilling technologies, which also includes thermal spallation (e.g., [6,[20][21][22][23][24][25][26][27][28][29][30][31][32]) and water jet drilling (e.g., [33][34][35][36][37]) and laser drilling (e.g., [38][39][40][41][42][43]) to name only some.…”

“…Despite numerous experimental studies, little work has been performed on simulating the underlying pore-scale physics during the electric breakdown of the rock. Li et al [15] studied the "Electrical Treeing Breakdown" approach by modeling the plasma formation in long fractures connecting the electrodes. Failure of the surrounding rock was modeled by propagating the channel pressure into the rock to determine if the induced stresses lead to fracturing.…”