Effect of fluid flow on Mode-I dynamic stress intensity factor in the presence of crack shielding in a poroelastic medium

This paper analyzes the Mode-I stress intensity factor (SIF) of parallel cracks in a poroelastic medium. In particular, we investigate the influences of crack shielding on fluid flow which in turn can further change the frequency-dependent behaviors of SIF. Numerical results reveal that the frequency-dependent behaviors of SIF are jointly controlled by fluid flow and the shielding effect which is characterized by a spacing ratio γ, the ratio of crack spacing to crack length. The SIF of permeable cracks decreases with frequency, implying that in short-term responses the fluid has insufficient time to flow between cracks and surrounding micropores so that the crack deformation is inhibited. In the case of γ≥10, the shielding effect is negligible so that our results reduce to that of a single crack for which the SIF decays the fastest when the wavelength of fluid diffusion roughly equals the crack length. For γ<1, the shielding effect can remarkably reduce the magnitude of the SIF over a broader frequency range and thereby enhance the effective material strength. In this case, the SIF decays the fastest at a higher characteristic frequency where the wavelength of fluid diffusion equals the crack spacing. For an intermediate value of 1<γ<10, the characteristic frequency is influenced by both crack length and crack spacing. In contrast, the effect of fluid flow on the SIF of impermeable cracks is much weaker. Our findings show that both the crack shielding and permeability of crack surfaces strongly affect the magnitudes and frequency-dependent behaviors of the SIF.