Mechanism of rock-bed scour due to impinging jet

Scour of rock bed downstream of high dams ismainly caused by the transient forces as a result of the propagation of fluctuating pressures, which is significantly controlled by the rock fracture-structure. The physical mechanism of rock disintegration and scour pool forming are analysed herein by considering the fracture- structure of rock bed. A two-dimensional discrete fracture network is imitated applying the Monte-Carlo method. The model of transient flow is established along with each discrete fracture to simulate numerically the propagation of fluctuating pressure waves. Applying the method of automatic tracing of rock blocks layer by layer, the mechanism of disorganization of fractured rock, both the transient physical and dynamic characteristics of isolated rocks, and the damage process of the rock bed are discussed. Finally, a stability criterion of rock blocks and the evaluationmethod of equilibrium scour depth are established.