Evaluating Methods for Measuring Rock Toughness in Hydraulic Fracturing: A Research Note

Rock toughness, a critical property, defines a rock's ability to resist deformation or fracturing.It is quantified through three primary modes: opening (Mode I), shearing (Mode II), and tearing (Mode III).Estimating rock toughness is essential for effective hydraulic fracturing, and three key tests developed to address this requirement are the scratch test, the straight-notched Brazilian disc specimen test, and the semicircular bend test.This paper aims to outline the procedures, governing equations, and results for each test, providing a detailed analysis of their outcomes.The study reveals significant correlations between rock toughness and shale properties.It also presents a comprehensive comparison of the three tests, focusing on their convenience, variable dependencies, and accuracy.However, a shared limitation across all methods is the technique used to induce fractures, which constrains their broader applicability.This highlights the need for further research to enhance the accuracy and practicality of fracture toughness measurement techniques.