Phase Field Modeling of Anisotropic Tension Failure of Rock-Like Materials

Abstract

The tensile fracture is a widespread feature in rock excavation engineering, such as spalling around an opened tunnel. The phase field method (PFD) is a non-local theory to effectively simulate the quasi-brittle fracture of materials, especially for the propagation of a tensile crack. This work is dedicated to study the tensile failure characteristics of rock-like materials by the PFD simulation of the Brazilian test of the intact and fissure disk samples. The numerical results indicate that the tensile strength of the disk sample is anisotropic due to the influence of pre-existing cracks. The peak load decreases at first and then increases with the increase of the inclination angle, following the U-shaped trend. The simulation results also indicate that the wing crack growth is the main failure characteristic. Moreover, the crack propagation path initiates at the tip of the pre-existing crack when the inclination angle is less than 60°. Crack propagation initiates near the tip of the pre-existing crack when the angle is 75°, and it initiates at the middle of the pre-existing crack when the angle is 90°. Finally, all cracks extend to the loading position and approximately parallel to the loading direction. This process is in agreement with the Brazilian test of pre-existing cracks in the laboratory, which can validate the effectiveness of the PFD in simulating the tensile fracture of rock-like materials. This study can provide a reference for the fracture mechanism of the surrounding rock in the underground excavation.

Mechanical Behavior and Fracture Characteristics of Rock with Prefabricated Crack under Different Triaxial Stress Conditions

“…For method (2), the effects of compressive stress and tensile stress on the fracture development of rocks with prefabricated fractures are analyzed separately. Once the prefabricated cracks on the two-dimensional plane are under the action of uniaxial compressive stress, once the cracks start, according to the experimental results and theoretical analysis of many scholars [44], wing cracks will be generated along the compression direction (Figure 13(c-2)). For the three-dimensional space, in addition to generating the airfoil crack surface P1 (Figure 13(c-3,c-4)), the crack surface P2 can also be generated in the direction perpendicular to the prefabricated crack.…”