考虑多场耦合高压电脉冲作用下岩体破碎响应

Response of Rock Breaking by High-voltage Electrical Pulse Considering Multi-field Coupling

基于电学理论、热学理论和力学理论建立高压电脉冲作用下岩体破碎多物理场耦合数值模型,提出一种考虑电击穿的电–热–力耦合数值模型揭示岩体在高压电脉冲下的破碎过程。利用随机分布模型模拟岩体中可能出现的导体矿物颗粒,综合分析电击穿过程中等离子体通道的形成规律。与现场试验进行对比,验证该数值模型的准确性。计算结果表明:击穿场强是主导等离子体通道形成的关键因素。岩体在高压电脉冲作用下的破碎过程可分为3个阶段,等离子体通道初步形成阶段、等离子体通道扩展阶段和等离子体通道形成阶段。在等离子体通道形成前,通道处的温度保持在500 K左右,应力达到10–2MPa左右;当等离子体通道形成时,温度和应力会在短时间内剧增,温度达到10~3 K,应力达到10 MPa。在电脉冲持续作用下,等离子体通道处的温度和应力持续增加。当最大应力超过岩体的临界应力强度后,岩体将发生破碎;同时通道也会继续分支扩展,更大范围地对岩体造成破坏。导体矿物颗粒会引导等离子体通道的形成,颗粒分布越密,对通道的形成越有利。脉冲电压到达峰值的时间越长,岩体的破坏速率相对越快。数值模型的计算结果有助于加深对高压电脉冲过程中岩体破碎过程的理解。

This study develops a coupled multi-physics field numerical model of rock breaking under the action of high-voltage electrical pulses based on electrical,thermal,and mechanical theories.Additionally,a coupled electro-thermal-mechanical numerical model that considers electrical breakdown is proposed to describe the fragmentation process of rock under high-voltage electrical pulses.The random distribution model is employed to simulate potential conductive mineral particles in the rock,and the formation of plasma channels during the electrical breakdown process is comprehensively analyzed.The accuracy of the numerical model is verified by comparisons with the experiments.The calculation results indicate that the breakdown field strength is a critical factor in the formation of plasma channels.The rock-breaking process under the influence of high-voltage electrical pulses can be divided into three stages:the initial stage of plasma channel formation,the stage of plasma channel expansion,and the stage of subsequent plasma channel formation.Prior to the formation of the plasma channel,the temperature and stress were approximately 500 K and 10–2 MPa,respectively;when the plasma channel formed,the temperature and stress increased abruptly within a short duration,with the temperature reaching 103 K and the stress reaching 10 MPa.The temperature and stress at the plasma channel continued to rise as the electrical pulse persisted.When the maximum stress exceeded the critical stress strength of the rock,the rock fractured;concurrently,the channel continued to branch and expand,causing extensive damage to the rock.The conductive mineral particles facilitate the formation of plasma channels,and the denser the particle distribution,the more favorable the channel formation.The longer the duration for the pulse voltage to reach its peak,the relatively faster the rate of damage in the rock-breaking process.The calculation results of the numerical model improve the understanding of the rock-breaking process during the high-voltage electrical pulse.