Experimental study of penetration for the analysis of pre-cut free surface parameters in rock materials based on response surface methods

Abstract

The strength of intact rock material is reduced after it has been cut by techniques such as water jets, based on which the use of disc cutter hobs for rock-breaking by hobbing has good economic results. The kerf is the free surface created by water jet cutting. The kerf depth, kerf spacing, and kerf angle are the main parameters affecting the rock-breaking force of the disc cutter, which can be simplified as the normal penetration load of the indenter. To investigate the effect of prefabricated notch parameters on the penetration load and the sensitivity of the response of penetration load to each factor, response surface tests were carried out on sandstone and granite specimens, and every factor’s impact on the penetration load was examined. The results showed that: (1) The single factor analysis and interactive analysis of the prefabricated kerf parameters for sandstone and granite samples showed that the penetration load was negatively correlated with kerf depth and kerf angle, and positively correlated with kerf spacing within the set range of the test. (2) The difference in rock strength can also affect the penetration load of the samples. In the prefabricated kerf-assisted rock-breaking test, for the high-strength rock samples represented by granite, increasing the prefabricated kerf depth can reduce the penetration load of the samples more effectively.