Experimental Study of Fracture Toughness and Subcritical Crack Growth of Three Rocks under Different Environments

This paper investigates fracture toughness and subcritical crack growth of marble, lherzolite, and amphibolite under different environments aiming to better understand the effect of environment, especially the acidic solution, on the fracturing behavior of the three rocks. Specifically, a series of load relaxation (RLX) and rapid loading tests were performed on double-torsion (DT) specimens to understand the subcritical crack growth velocity V versus the stress intensity factor K-I relation and evaluate the fracture toughness K-IC for the three studied rocks in air, distilled water, and acidic solutions with pH of 6.0 and 3.0, respectively. The results indicate that, for all three studied rocks, the percentage of load drop during RLX increases and the fracture toughness decreases when the environmental condition changes from air to distilled water and to an acidic solution with higher acidity. The measured log K-I-log V relation follows the Charles theory well, and the crack velocity and the final crack growth length both increase and the subcritical crack growth index n decreases when the environmental condition changes from air to distilled water and to an acidic solution with higher acidity. The results also show that the weakening effect of an acidic solution on the marble is much greater than that on the lherzolite and amphibolite. (c) 2020 American Society of Civil Engineers.