The Effect of Dynamic Stress Cycling on the Compressive Strength of Rocks

Abstract

AbstractQuasi‐static rock strength is a nonconservative property, as fatigue during cyclic loading reduces the macroscopic strength. When strain rate under compressive loading increases above a lithology‐specific threshold, the primary failure mechanism transitions from localized failure along discrete fractures to distributed fracturing. However, the role of load path under high strain rate conditions has not been explored in any detail. We examine the effect of rapid stress cycles on the dynamic compressive strength of Westerly Granite using a modified split Hopkinson pressure bar approach and explore the implications of our results for the formation of pulverized fault zone rocks. Under cyclic loading conditions, the compressive strength can be reduced by a factor of 2, demonstrating that, like the quasi‐static strength, the dynamic rock strength is also a nonconservative property. Therefore, traditional high strain rate experimental approaches utilizing simple load paths may overestimate strength when rocks are subjected to complex load paths.