Fractures: Tension and Shear

The article delves into the intricate mechanisms of tension and shear in rock fractures, drawing from observations made in both field and laboratory settings. It underscores the critical role of the observational cycle in scientific and engineering methodologies, demonstrating how repeated observations can deepen understanding. The paper begins with a keynote lecture presented at the 2019 ARMA symposium, which emphasized the importance of observations in understanding arching and rock fracture mechanisms. Through a series of illustrations and models, the author explores the phenomenon of intact rock bridges and how they break or fracture, leading to insights into the fundamental tension and shear mechanisms. The observational cycle is applied multiple times, starting from field evidence and moving to controlled laboratory experiments, where advanced observation methods like high-speed video and acoustic emissions are used. The paper concludes by highlighting the necessity of repeating the observation cycle to gain a thorough understanding of the fracturing processes, emphasizing the interplay between observations and abstractions (models). This comprehensive approach sets the article apart, offering a detailed and nuanced understanding of rock fracture mechanisms.