Saturation effects on mechanical excavatability of Roubidoux sandstone under selected rock cutting tools.

摘要

This study investigated the differences in the cutting performance of two rock cutting tools in dry and saturated rock. For this purpose, a permeable quartzose sandstone was subjected to a series of full scale linear rock cutting tests, in both dry and saturated conditions, using a constant cross-section (CCS) disc cutter and a radial drag pick at a constant cutting speed.;In this rock, saturation with water reduced the forces acting on the disc cutter by 27-48% (significant at 90% confidence), but also reduced the chip yield by nearly as much. Even though the specific energy of fragmentation went down 8-10%, the difference was not statistically significant.;Contrary to the behavior under the disc cutter, water saturation increased the drag pick cutting forces by 9-10%, which is suggestive but not enough to be statistically significant. It did not increase the chip yield by a concomitant amount, however, so the specific energy went up by 28% (significant at 90% confidence).;The unexpected differences in the effect of water saturation on the rock fragmentation response to these cutters might be explained by the effects due to their different fragmentation mechanisms, such as the relative size of the crushed zone that forms beneath the cutters. The relationship between cutting speed and rock permeability was expected to be a major factor influencing the effective pressure beneath a cutter in saturated rock. However, load-indentation tests with pore pressure measurement at the same speed showed that the pore pressure within the tested sandstone remained too low to affect the rock fracture process. Other possible mechanisms are discussed.