Load-indentation testing to assess porewater pressure effects on linear drag and disc cutting of a saturated permeable brittle rock

Abstract

In this study load-indentation tests with porewater pressure measurement were conducted to explore the unexpected differences owing to water saturation in the linear cutting of a permeable quartzose sandstone using drag and disc type cutters. This was done to evaluate the probable role of porewater pressure in rock fragmentation by drag and disc type cutters. The contrasting response to water saturation of these two types of cutters might be explained by the effects of 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.