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

Abstract

Electropulse rock breaking has wide application prospects in hard rock drilling and ore breaking. At present, there are no suitable physical mathematical models that describe electropulse boring (EPB) processes under confining pressures. In this paper, a high-voltage electropulse breakdown damage model is established for granite, which includes three submodels. It considers electric field distortions inside the rock, and an electric field distribution coefficient is introduced in the electro-breakdown model. A shock-wave model is also constructed and solved. To simulate the heterogeneity of rocks, EPB rock breaking in deep environments is simulated using the two-dimensional Particle Flow Code (PFC2D) program. The solved shock wave is loaded into the model, and confining pressure is applied by the particle servo method. An artificial viscous boundary is used in the numerical simulation model. Using this approach, a complete numerical simulation of electropulse granite breaking is achieved. Breakdown strength and the influences of physical and mechanical parameters on it are also obtained. Time-varying waveforms of electrical parameters are obtained, and the effect of confining pressure on EPB is also described.

Stress wave analysis of high-voltage pulse discharge rock fragmentation based on plasma channel impedance model

“…development of the plasma channel, the maximum particle density is 8.95×10 26 m −3 , the maximum temperature is 70.89×10 3 K, the peak value of the shock wave is P m =808.6 MPa, and the peak time t r =0.86 μs. The model calculation results are of the same order of magnitude as in some studies [10,11].…”

“…where ε sublimation is the energy required to sublime the surrounding solid medium into plasma, ρ 0 is the density of the solid medium in the undisturbed region, and α and β are coefficients: α=300.1 MPa, β=300 MPa [20,25]. Solving equations (2), ( 4), ( 5), (10)…”

“…In past studies, the time-varying plasma channel resistance in solids was mostly estimated by empirical formulas. In the derivation process, only the influence of the internal energy of the channel was considered, and the rest of the energy was regarded as a fixed value, thus introducing errors [10,11]. During the discharge process, due to the rapid injection of energy, the plasma channel expands rapidly under the Joule heating effect, the temperature rises rapidly, and the channel radius and conductivity change with time.…”

The Utilization of a Coupled Electro-Thermal-Mechanical Model of High-Voltage Electric Pulse on Rock Fracture

“…However, they did not consider the case of changing conductivity and continuous increase in energy release. On the basis of uniform channel radius [ 32 , 33 ], Kirchhoff’s equation, energy conservation, and other theories [ 23 ], Li et al [ 34 , 35 ] calculated the mechanics of electric pulse rock-fracturing impact following plasma channel development. Extremely complex and frequently accompanied by electric-thermal-force multi-field coupling, the EPB procedure is characterized by a high degree of complication.…”

The fragmentation mechanism of granite in electrical breakdown process of plasma channel drilling

“…Plasma Channel Drilling (PCD) is a new method (Timoshkin et al 2004;Inoue et al 2000), which has been widely used in mining and rock excavation (Yan et al 2016), mineral decomposition (Andres et al 2001;Huang and Shi 2020) and recycling of valuable resources (Duan et al 2015), etc. PCD has the significant advantages of high drilling efficiency and low cost (Biela et al 2009;Li et al 2019;Zhang et al 2017). In conventional drilling, based on hard interaction with the rock, the bit relies on its own scraping and shearing to cause damage to rock.…”