An experimental study of the effect of temperature on teeth breaking efficiency based on rock mechanical properties

To master changes in rock mechanical properties and the impact of high temperature on rock-breaking efficiency, the rock mechanical properties of granite, limestone, and sandstone under different temperatures and single-tooth static-pressure experiments were studied. The results show that the compressive strength, shear strength, internal friction angle, and elastic modulus of granite and limestone initially increased and then decreased as the temperature rose. The experimental temperatures were 25 °C, 100 °C, 200 °C, 300 °C, 400 °C, and 500 °C. The mechanical properties of granite reached the maximum at 200 °C, while those of limestone reached the maximum at 100 °C. The compressive strength, shear strength, and internal friction angle of sandstone gradually diminished, while the elastic modulus gradually increased at the abovementioned five temperature points. Among the samples of granite, limestone, and sandstone, the crushing-specific work of conical teeth, wedge teeth, and scoop teeth was smallest when the temperature was 300 °C. Compared to the normal temperature, the load of conical teeth, wedge teeth, and scoop teeth was reduced by 32.1%, 28.4%, and 22.9%, respectively, when they were pressed into sandstone. At the same temperature, the conical tooth had the highest rock-breaking efficiency, followed by the wedge tooth; the scoop tooth had the lowest efficiency. Conical teeth can be used to select the tooth shapes of bits to improve drilling efficiency. Optimizing the tooth profile and conducting research on rock-breaking efficiency under different temperatures and rocks have an important role in bit design and can greatly improve drilling efficiency.