Analysis of the stress wave effect during rock breakage by pulsating jets
Formation, propagation and attenuation of stress waves during rock breakage by pulsating jets are simulated by introducing the Johnson-Holmquist-Concrete nonlinear constitutive model, and using the smoothed particle hydrodynamics approach. The curve of stress over time at different locations of the rock surface under the action of high-velocity pulsating jets is obtained, as well as relationship curve between amplitude of stress wave and distance to jet action spot. Based on the computational results, breakage behavior of rocks under stress wave effect, and impacts of jet velocity and rock properties on stress wave effect are analyzed. The results show that the stress wave effect of pulsating jets is rather strongly localized, and the amplitude of stress wave decreases sharply with increasing distance to jet action spot. The intensity and effect range of stress wave are in direct proportion to jet velocity; besides, there is a threshold velocity regarding macroscopic failure of rocks. Rocks of different lithologies have somewhat different failure modes under stress wave action of pulsating jets; failure mode of low strength rocks like sandstone is mainly crack propagation under tensile stress during rock loading and unloading processes, whereas the failure mode of hard brittle rocks such as limestone and granite is mainly longitudinal failure caused by stress concentration.