Rock Fracturing under Pulsed Discharge Homenergic Water Shock Waves with Variable Characteristics and Combination Forms

Abstract

High voltage pulsed discharge in water (HVPD) is used throughout industry for fracturing both natural and man-made materials. Using HVPD, we modeled crack propagation of rocks under homenergic water shock waves (HWSW) with different characteristics and combination forms using a combination of experimental analysis and numerical simulation. The experimental results show that, under the same discharge energy (2 kJ), water shock waves (WSW) with different characteristics fractured the rock mass distinctly different. With a higher the peak pressure ( ) of WSW, more long cracks and microcracks were formed, creating a larger damage area. The numerical simulation results show that a single HWSWs impact with different characteristics will still only cause three long cracks to be well developed and almost no microcracks, when of HWSW was 3 MPa. With the increase of , the number of both long cracks and microcracks increased. This is consistent with the experimental results. When the peak pressure became greater than 15 MPa, crack propagation gradually became concentrated and the surrounding borehole wall became more severely broken. The rock model had optimal fracturing under the impact of the HWSW with a of 10 MPa. Also, the simulations showed that, under repeated-impacts of HWSWs with consistent characteristics, the fracturing characteristics were basically identical to those by a single-impact. While under the repeated-impact of HWSWs with variable characteristics, there was almost no relationship between the fracturing effect and the sequence of repeated-impacts. Finally, under a single-impact of HWSW with low and hydrostatic pressure ( ) acting within an initial crack (similar to hydraulic fracturing in a hydrocarbon well), the initial crack had excellent propagation with an increase in hydrostatic pressure. However, when of HWSW was too high, increasing had no effect on initial crack propagation.

Phenomenological Studies for Optimizing Subsonic Underwater Discharges

“…) Equations (13)(14)(15) will allow us to determine the main parameters responsible for the generation of a peak pressure ppeak as:…”

Experimental Study on Pressure Wave Characteristics of High-Voltage Discharge in Water With Hemispherical Electrodes

“…In the related research of rock breaking [7] and fracturing coal [30], it is necessary to put the discharge electrode into the drilled hole of rock or coal in advance. The borehole was also filled with incompressible liquid (water) to ensure low deformation energy loss and high transmission efficiency [31].…”

“…In 1938, Yutkin [1] proposed the industrial applications of high voltage electrical pulses. Since then, the high voltage electrical pulse technology has seen significant developments and successful applications in many fields, such as sewage treatment [2,3], hydraulic electric sand cleaning [4], extracorporeal lithotripsy [5,6], rock fragmentation [7], oil reservoir removal and fracture creation [8], and new nanomaterial synthesis [9].…”

A Semi-Analytical Solution for Shock Wave Pressure and Radius of Soil Plastic Zone Induced by Lightning Strikes

“…From the arc channel collision expression of Engel et al [ 15 ], which shows that the arc channel radius increases with time, it is not in line with the actual development of the arc channel law. Numerous analytical solutions have been provided to forecast water shock waves induced by arc discharges [ 16 , 17 , 18 , 19 , 20 , 21 ]. A physical and mathematical model of electro bursts has been provided to forecast the shock wave pressure generated by the expanding plasma channel [ 22 , 23 ].…”