The Numerical Simulation Of Rock Breaking Efficiency Of The Water Jet In Submerged State

With the exhaustion of the land resources, people have looked to seafloor to meetenergy demand. Due to the change of seafloor-pressure and the complex and changingworking conditions, there are many limitations to exploit mineral resources such as coal,petroleum, metallic nodule mineral and so on through the traditional mining method.Therefore, to study a kind of seafloor resources mining technology which is safety, highefficiency, non-pollution is an extremely urgent task. Because water jet miningtechnology has advantages such as no pollution, no hot reaction areas, smallcounteractive and high drilling efficiency and so forth, now it has been applied to theocean engineering.At present, because of the unclear rock breaking mechanism and many influencefactors of submerged water jet, and the poor transparency of the rock material, it isdifficult to observe the rock internal stress and strain and capture other relatedinformation when water jet is impacting the rock. So it is particularly important to studythe rock breaking efficiency and mechanism of submerged water jet further. Bycombining the numerical simulation method with theoretical analysis method, the paperstudy the effect of water jet parameters on rock breaking efficiency and the rock internalstructure deformation situation under the impacting of water jet, and obtain thefollowing useful results:（1）The paper uses nonlinear dynamic finite element method and the penaltyfunction coupling way to realize the coupling of jet and the rock, and establishes thenumerical model of water jet breaking rock in the submerged state.（2）With the increase of the jet velocity, the erosion depth adds quickly with itwhile the effect to the erosion aperture is smaller. When jet velocity is greater than500m/s, erosion depth will no longer add significantly when jet velocity increased, butgradually become stable. Therefore, according to optimal economy, the rock breakingvelocity of500m/s is the best.（3）With the increase of jet distance, the erosion depth of rocks decreases quickly,but the erosion aperture increases to a certain extent. The change in the erosion depthsand the erosion apertures do not appear the optimal jet distance, but the volume of rockbreaking has the optimal jet distance which is5mm. At the same time, the minimumvelocity of rock breaking at the different jet distances is acquired through simulation. Once reaches the minimum velocity of rock breaking, with the increase of the jetvelocity, the increase of erosion depth is divided into two phases.（4）With the increase of the jet diameter, the erosion depth is nearly invariable,but the erosion aperture adds rapidly and increases linearly. And the erosion aperture isrelated more to the jet diameter than the jet distance.（5）The moment when water jet and rock are touching, on the edge of contactareas of the water jet and rock is the biggest plastic strain area which is the earliestdamaged area. As the jet velocity and jet diameter increase, the axial and radial plasticstrain of rock increase quickly, and the axial plastic strain is higher than the radialplastic strain. Rock deformation process can be divided into three stages：compaction,stable deformation and unloading.