On the failure pattern of sandstone impacted by high-velocity water jet

• Lots of experiments of high-velocity water jets impacting sandstone were conducted.
• Scanning electron microscopy (SEM) was used to examine the fracture morphology.
• Three different failure patterns of sandstone were observed.
• The water jet velocity interval to the generation of transverse cracks was found.

Impingement of rocks by high-velocity water jets causes the erosion of structures, yet is also the principal process for non-traditional drilling and cutting methods, such as hydrodemolition, hydrodynamic fragmentation and cavitating drilling. The failure patterns of rocks subjected to water jets with different velocities vary greatly. Based on the theoretical studies, lots of experiments were conducted selecting water jets with velocities ranging from 157 ± 1 m/s to 774 ± 1 m/s. Scanning electron microscopy (SEM) was used to examine the fracture morphology in order to better understand the damage mechanism of sandstone. It's indicated that it will experience three different failure patterns in the bulk of sandstone under different jet velocities: (i) the center broken pit surrounded with a circumferential crack on the surface when the jet velocity is above a threshold value between 157 m/s and 316 m/s; (ii) the internal fractures constituted of circumferential fractures, radial fractures and the conical fractures; (iii) the macrocracks on the side surface, which change from transverse cracks to split-like cracks with the increment of jet velocity.