Experimental and Theoretical Study on Crack Growth Using Rock-Like Resin Samples Containing Inherent Fissures and its Numerical Assessment

The initiation and propagation of microcracks along preexisting fissures is one of the typical failure modes for inherently fractured rocks in geotechnical engineering. To better capture the growth of such microcracks, an improved transparent rock-like resin sample with preexisting fissures is first proposed and applied in three-dimensional uniaxial compression test to vividly reproduce the dynamic growth of microcracks due to fissures reactivation. An analytical mathematical solution for calculating the growth length of wing-shaped cracks is derived with the help of the composite fracture strength criterion. The theoretical values agree well with the experimental results. In addition, further investigations on the microcracking mechanism as well as its influence factors induced by the combined interaction of double parallel fissures are carried out under the framework of particle flow simulations. Results suggest that the microcracks induced by fissure reactivation, they begin to appear when the loading stress reaches 50% of the peak stress (σ_p), develop rapidly after surpassing 70% σ_p and expand more slowly beyond 80% σ_p. Especially in the case of double-fissures, some counter-wing and petal-shaped cracks will finally form in the later stages of microcracks propagation, with a length of approximately 1/3–1/2 of the minor axis of the preexisting fissures.