Support type influence on rock fracture toughness measurement using semi-circular bending specimen

Abstract

In the present manuscript, the importance of support type on accurate determination of rock fracture toughness in semi-circular bending (SCB) test is demonstrated. First, by employing the finite element (FE) method, a detailed study is conducted to assess the effect of support friction on the mode I stress intensity factor (SIF) in the SCB specimen. Then, three different rocks and three various support types are utilized to investigate the support type effect experimentally. Both the FE and experimental results show that utilization of different types of supports results in different friction coefficients between the SCB specimen and the bottom supports. This can generate significant errors in calculations of SIF and fracture toughness of rock samples. It is shown that using the fixed or roller-in-groove support types can generate a large amount of error in rock fracture toughness calculations, although, these types of supports are still commonly being used by researchers.