The influence of the rake angle on the excavation energy in a sandstone

The inclination of the cutting bits has a strong influence on the excavation energy in rocks. As matter of fact, a correct prediction of the cutting forces acting on the bits is very important to geotechnical engineering. Several cutting tests at 1 m/s cutting velocity (with different rake angles and penetration values) were performed on a sandstone (Ruhrsandstein). The results were interpreted using the models of Evans and Nishimatsu. The optimum angle of inclination which reduces the horizontal cutting forces in this material with this cutting velocity was found to be 49°. The specific excavation energy was also calculated. It was found that it does not change with the penetration, but depends only on the rake angle and on the geotechnical properties of the sandstone.