为探究组合电压水中放电对煤岩体的损伤作用及裂纹扩展演化规律，在煤岩体钻孔水中（静水压为3 MPa）进行组合电压放电试验，并利用声发射技术（AE）和PFC2D数值模拟分析组合电压放电作用下煤岩体损伤和裂纹发育特征及不同因素对致裂效果的影响。研究结果表明：单一电压作用下，AE最大振铃计数、累计振铃计数随着放电次数的增加整体上呈现减小的趋势；组合电压作用下，AE最大振铃计数及累计振铃计数在改变电压时急剧增加，AE最大振铃计数增幅179.6%，累计振铃计数增幅124.3%，振铃计数总量增长趋势比单一电压放电更快。单一放电电压作用下，到达一定放电次数后再次放电基本不再产生新生事件；组合电压可以使AE事件数量在改变电压后急剧增加，新生的事件源幅值更高，分布范围更广，事件的增加趋势明显高于单一放电。组合电压放电在改变电压时，产生大量新生裂纹，且放电产生的能量被优先用于新生裂纹的扩展，最终放电12次后裂纹相比单一电压放电，产生的主裂纹数量更多，且各主裂纹长度相差较小，更均匀，致裂效果更好。在组合电压放电中，不同电压跃迁次数及电压梯度下的裂纹均是在改变电压时增长增长较多，最终放电12次后各组的裂纹数量相差较小；随着电压跃迁次数及电压梯度的增加，外界输入能量越小，但裂纹增长趋势越快，主裂纹数量越多，长度分布越均匀。

To investigate the damage effect and crack propagation evolution of coal rock under combined voltage discharge in water, combined voltage discharge experiments were conducted on coal rock boreholes in water (hydrostatic pressure of 3 MPa). Acoustic emission (AE) and PFC2D numerical simulation were used to analyze the damage characteristics and crack propagation in coal rock subjected to combined voltage discharge, as well as the influence of different factors on the fracturing effect. The research results indicate that: Under single voltage discharge, the maximum AE ring count and the cumulative ring count generally decrease as the number of discharges increases. In contrast,under combined voltage discharge, both the maximum AE ring count and the cumulative ring count increase sharply when the voltage changes, with a 179.6% increase in the maximum ring count and a 124.3% increase in the cumulative ring count. Overall, the total ring count increases at a faster rate compared to single voltage discharge. Under single voltage discharge, after a certain number of discharges, there are almost no new AE events. In constrast, combined voltage discharge results in a significant increase in the number of AE events after voltage changes, with the new event sources exhibiting higher amplitudes and a broader distribution. The increase in events is more pronounced compared to under single voltage discharge. During combined voltage discharge, a large number of new cracks are generated when the voltage changes. The energy released during the discharge is primarily utilized for the expansion of these new cracks. After 12 discharges, more primary cracks are generated compared to single voltage discharge, and the lengths of these cracks are more uniform, resulting in better fracturing effects. In combined voltage discharge, under different voltage transition frequencies and gradients, most crack growth occurs when the voltage changes. After 12 discharges, the number of cracks across different groups becomes similar. As the number of voltage transitions and the voltage gradient increase, less external energy is required; however the crack growth rate accelerates, the number of primary cracks increases, and the length distribution of the cracks becomes more uniform.