In order to simulate the transition of rock from continua to discontinua more accurately and reduce the mesh dependence

an element splitting method is developed based on the continuum-discontinuum method where the Lagrangian element method is coupled with discrete element method. The computational domain is discretized into high-precision quadrilateral elements; after cracking

the cracks can propagate along the diagonal lines of quadrilateral elements and the edges of triangular or quadrilateral elements. Deformation-cracking processes of the Brazilian disc rock specimen

uniaxial compression rock specimen and surrounding rocks under hydrostatic pressure are simulated. The following results are found. (1) For the Brazilian disc rock specimen

tensile cracks propagate from the center of the disc to the top and bottom until they penetrate through the disc

and the tensile cracks are relatively smooth; for the uniaxial compression rock specimen

shear cracks are relatively straight

and the direction of the main shear crack penetrating through the rock specimen is consistent with the shear plane direction obtained according to the Mohr-Coulomb criterion. (2) From the effects of hydrostatic pressure and internal friction angle on deformation-cracking processes

the following results are found. Under hydrostatic pressure

firstly

V-shaped notches appear near the cavern surface due to shear crack propagation; then

long and curved shear cracks appear due to further shear crack propagation whose distribution is similar to shear slip-lines. With an increase of hydrostatic pressure

the ranges of shear cracks increase

whereas with an increase of internal friction angle

the ranges of shear cracks decrease

and the angle between the propagation direction of the long shear crack and the annular direction decreases. (3) According to the simulation of the surrounding rock in phase-Ⅱ Tianshengqiao hydropower station

four V-shaped notches are observed

which is in a good agreement with field observation.