Experimental investigation on rock fracturing performance under high-pressure foam impact

Abstract

In view of the more extensive demand for hard rock crushing in mining and engineering, the traditional drilling and blasting method needs to be reviewed. The drilling and blasting method has drawbacks such as the need for complex rock-breaking procedures and associated poor safety, there can also be difficulties in drilling equipment excavating hard rock. The property of rock, that is the tensile strength is far less than the compressive strength is adopted in the investigation, and an innovative method, using high-pressure foam, is used to crush hard. Based on the continuity equation of foam flow and the tensile-water wedge rock-breaking theory of high-pressure water jet impacting, an experimental rock fracturing system was established. The relationships between the rock fracturing performance, foam pressure, hole depth, and rock compressive strength were demonstrated. The results show that increasing the pressure of the foam generation system is beneficial to the process of damaging the rock specimen, but the position of the main crack in the direction of the drilling depth is not affected. The rock failure area decreased by about 71% and the rock fracturing pressure increased by 116.5% when the compressive strength of the rock increases from 6.88 MPa to 21.17 MPa. Thus, the rock compressive strength has an obvious exponential inhibitory effect on the rock crack propagation. In addition, under the condition of the same hole diameter, the optimum rock-breaking effect was achieved at a depth of 200 mm, and the fracture form changed with the increase in hole depth.