Research on Adaptability of CS and BT Hobs to Break Soft and Hard Rock

To study the breaking differences between CS hob and BT hob under hard rock (rust rock) and soft rock (red sandstone), and reveal their adaptability in the two rock formations, the vertical breaking experiments of two hobs are conducted. Then, the rock breaking load, rock breaking difficulty coefficient, and rock breaking efficiency of the two hobs in different hob spacings are analyzed and discussed. The result denotes that the CS hob has a greater rock breaking load and rock breaking difficulty compared to the BT hob. Meanwhile, when the breaking object changes from hard rock (rust rock) to soft rock (red sandstone), both types of hobs’ rock breaking loads decrease, but the CS hob’s decrease is significantly greater than the BT hob’s. Meanwhile, the optimal hob spacing for the CS hob increases from 40 mm to 50 mm, whereas for the BT hob, it remains at 30 mm. Considering the rock breaking load and rock breaking efficiency of the hobs together, the CS hob is found to be more suitable for soft rock formation, while the BT hob is more suitable for hard rock formation.