Determining Tensile Strength of Rock by the Direct Tensile, Brazilian Splitting, and Three-Point Bending Methods: A Comparative Study

Abstract

To accurately obtain the tensile strength of rock and fully understand the evolution process of rock failure is one of the key issues to the research of rock mechanics theories and rock mass engineering applications. Using direct tensile, Brazilian splitting, and three-point bending test methods, we performed indoor and numerical simulation experiments on marble, granite, and diabase and investigated the tensile strength and damage evolution process of several typical rocks in the three different tests. Our experiments demonstrate that (1) the strength is about 10% greater in the Brazilian splitting than in the direct tensile, while the tensile modulus is lower; it is the highest in the three-point bending, which is actually subjected to the bending moment and suggested as one of the indexes to evaluate the tensile strength of rock; (2) the strength in splitting tests is strikingly different, while the strain law is basically similar; the direct tensile test with precut slits is more attainable than that with no-cut slits, with an uninfluenced strength; (3) the failure modes of rocks using different methods are featured by different lithology, while their final modes are basically the same under the same method; (4) PFC and RFPA numerical simulation tests are effective to analyze the internal crack multiplication and acoustic emission changes in the rock as well as the damage evolution process of rock in different tests.

Assessing water-induced changes in tensile behaviour of porous limestones by means of uniaxial direct pull test and indirect methods

“…However, the mechanical response of these geomaterials under tensile stress and its water-induced variation have been poorly analysed due to the difficulties in tensile testing (Briševac et al, 2015;Hashiba and Fukui, 2015;Okubo and Fukui, 1996). This is a relevant research topic because the tensile failure of rock masses is the main failure mode in engineering practice (Huang et al, 2021;Liao et al, 1997;Zhang et al, 2018). In particular, an understanding of the rock behaviour under tension is of paramount importance in the design, execution and stability analysis of underground structures such as galleries, mining roofs, storage caverns, tunnel boring, drilling or blasting (Coviello et al, 2005).…”

Crack Initiation Prediction in Rock Samples using Digital Image Correlation

“…This may be due to the technical challenges associated with measuring the very small displacements and strains that occur at the early stages of crack initiation (Liwang , Haibo , Xiaofeng, Di , & Guokai , 2020). Besides, direct tensile (DT) tests are typically more difficult than compressive tests for several reasons, such as: specimen preparation, loading direction, and failure mode (Huang, et al, 2021;Kittitep & Sippakorn, 2010). Therefore, in this paper we would like to invest in methods that could find the crack initiation under tensile stress before it is noticeable through visual inspection.…”