Rock breaking performance of disc cutter assisted by circumferential pre-slotting

Disc cutter has a better hard rock breaking performance due to its undercutting mode. To further improve the mechanized excavation efficiency of hard rock roadway in underground coal mine, the rock wedged performance of disc cutter assisted by circumferential pre-slotting was investigated. Based on the rock wedged tests by disc cutter, the mechanism of rock wedged by disc cutter has been understood, and the influencing mechanism of the circumferential pre-slotting on rock fracturing has been revealed. The effects of cutting parameters and slotting parameters on the rock breaking performance of disc cutters were comprehensively evaluated by taking the cutter load, rock fragments volume and specific energy of rock-breaking as indicators, and the significance of the effects of various factors on the rock breaking performance and the corresponding parameter matching relationship of the optimal rock breaking performance of disc cutter were obtained by orthogonal test. The results show that the rock wedged process by disc cutter can be divided into three stages based on the characteristics of cutter load fluctuation and acoustic emission ringing caused by rock fracturing, namely, compressive stage, stress accumulation stage and fragmentation stage. At the condition of same cutting depth, the cutter load and stress with a slotting depth and width is 16 mm and 3 mm decreases more than 40% and 20% respectively compared to that without pre-slotting condition. Based on the orthogonal test with three-factor and four-level, the matching relationship between cutting depth, slotting depth and slotting width under the optimal rock breaking performance is 30, 16 and 3 mm. The cutting depth has the most significant effect on the rock breaking performance of disc cutter, followed by slotting depth and slotting width. The cutter load and rock fragments volume are positively correlated with cutting depth. The specific energy of rock breaking decreases first and then increases with the increase of cutting depth, and the minimum value is at 30 mm. Each index decreases first and then increases with the increase of slotting depth, and the optimal value is 16 mm. When the slotting width exceeds 3 mm, the influence of slotting width on each index is not significant. Circumferential pre-slotting has a good effect on improving the rock wedged performance of disc cutter. At the same time, it is beneficial to improve the loading conditions of disc cutters and prolong the service life of cutters, so as to provide some guidance and reference for the design of disc cutter.