Abstract：The process of rock breaking under water jets impingement is quite complicated. When high pressure water jets impact saturated rock，three materials interact with each other including jet-pore fluid，jet-rock and pore fluid-rock interactions. A numerical analyzing model of the system is established according to fluid-structure interaction theory. In the model，the standard k-epsilon two equations and control volume method for water jets，and the elastic orthotropic continuum and finite element method for the rock are adopted. Also，a numerical algorithm for the materials is given. The fluid field characteristics and stress distributions in the system are computed under the condition when water jets with 447.2，547.7 and 632.5 m/s respectively impinge the rock using the model and algorithm. The numerical results show that the potent core length is about 10 times the diameter of the nozzle. The radial impact pressure takes on normal distribution，and the impactful range is about 3.5 times of the nozzle diameter as the standoff is about 45 times of the nozzle diameter. When water jet impinges the saturated rock in which fluid flows according to the Darcy¢s law，the pore pressure decreases rapidly as the depth increases under rock surface，and spreads about 7 times of the nozzle diameter along the rock symmetry line. Meanwhile，the maximum principal stress lies under the impact center about 0.4 time of the diameter of the nozzle away. Tension stress causes mainly the rock failure and the crack starts internally and spreads toward the impact surface. The investigation affords a new method for studying the mechanics of rock failure due to water jets impact.
