Experimental investigation on rock fragmentation charactersitics of pressurized pulsed water jet.

As a novel type of pulsed water jet (PWJ), the pressurized pulsed water jet (PPWJ) shows great potential in the field of rock fragmentation engineering. In this study, the macro and micro morphologies of erosion craters on different targets (sandstone and granite) were measured to investigate the rock fragmentation characteristics of PPWJ. The results show that the fragmentation processes of granite and sandstone are significantly different from each other. The erosion craters on the sandstone surface exhibit a conical shape, with fragmentation manifesting as the successive exfoliation of mineral particles; the main destruction pattern of sandstone is the fracture of the bonding surfaces between particles. In contrast, the erosion craters on the granite surface assume a spoon-like form, with fragmentation presenting as flake-like exfoliation caused by the expansion of internal fractures; the main destruction pattern of granite is intragranular and intergranular fracture. The erosion volume of granite is much larger than that of sandstone, indicating that PPWJ-induced fragmentation of brittle and hard rock is more likely to form large-volume spalling. Under the same conditions, compared with continuous water jet (CWJ) and interrupted pulsed water jet (IPWJ), the specific energy consumption of rock fragmentation by PPWJ is reduced by 60.2% and 54%, respectively. The results of this study are expected to lay the foundation for promoting the application of PPWJ in rock fragmentation engineering.