Mechanism on energy dissipation and release of rock breakage with high pressure water jets

If the criterion of rock breakage with high pressure water jets is developed based on stress-strain,the preci-sion of the criterion depends on the function type of yield stress. And the precision is not high enough for rock break-age with high pressure water jets,because of being lack of critical rock parameters. But if the criterion is developed based on energy,its precision will be high enough and its applicability will be general. The paper studied the mecha-nism of rock breakage with high pressure water based on energy dissipation and release. The kinetic energy of potential core area and boundary layer was calculated based on the velocity distribution of free jet,and then the kinetic energy calculation model of high pressure water jets was developed. The rock breakage energy of high pressure water jets re-presented the formation of erosion pit and volumetric fracture of rock. Part of energy dissipated fracture propagation and slip plane. And part of energy reserved as elastic potential energy in rock,which leaded to the volumetric fracture of rock. According to the unified energy yield criterion of rock,the energy criterion of rock breakage with high pressure water jet was developed. The primary rock parameters of sandstone,limestone and granite were tested by uniaxial com-pression experiment. Then the shear strain energy and volumetric energy of three type rocks can be calculated respec-tively. So,the critical speed of high pressure water jets can be figured out. According to the experimental results of rock breakage,the energy criterion of rock breakage with high pressure water jet was amendment,combining with the dis-charge coefficient of nozzle. The amended criterion was more precise for coal breakage with high pressure water jets. And the failure mode of rock proved that the energy criterion was more suitable for the mechanism of coal breakage with high pressure water jets.