The process of high-pressure submerged jet cutting hard soil is recorded and analyzed in real-time with high-speed camera, and the failure mechanism and active rule of the soil under vertical high pressure jet are studied. The results show that the diffusion ranges of the high-speed flow into the hard soil increase gradually, and the "mushroom" form of the slurry diffusion pattern. When the jet pressure is larger, the "mushroom" type slurry diffusion pattern is more significant. At the same target distance, as the moving speed increases, the cutting depth decreases gradually, and the rate of attenuation increases with the increase of the jet pressure. The cutting section is a certain slope at different jet pressure and the cutting process is not uniform. The uniform cutting phenomenon has a significant significance to improve the high-pressure system of the trailing suction hopper dredger. Because the draghead fixed high pressure nozzle will increase the initial cutting depth. When the draghead move forward, the high pressure flush with teeth cut hard soil more quickly and effectively, thus improving the cutting efficiency of hard soil.
High pressure water jet cutting technology is an important part of the application of water jet technology and has been applied in many engineering fields (sun, 1992; li, 1997; shen, 1998). In dredging projects, for example, high-pressure jet can be used to assist dredging operations of harrow suction vessels, pre-cutting hard clay and improving the cutting efficiency of draghead teeth. Due to the superposition of various complex relationships such as soil dynamic changes, water jet impact load changes and fluid-soil interaction (Tian, 2003; Arnold, 2013), the related numerical simulation and experimental research are more difficult. The failure to accurately reveal the inherent mechanism and real physical process of high-pressure water jet cutting hard soil largely affects the development and application to dredge engineering.
