Theoretical and experimental study on the mechanical measurement of rock tensile fracture by ring radial compression

Conventional Brazilian disc splitting tests are hampered by stress concentration at the loading points, leading to test outcomes that do not truly represent the engineering failure strength of rocks. To enhance the accuracy of these tests, the specimen shape has progressed from the Brazilian disc to a circular ring. This study presents a theoretical analysis of the compression deformation process in circular rings, followed by platform-radial compression tests conducted on various types of rocks and metals, employing the digital speckle correlation method (DSCM) alongside an improved mechanical extensometer. The findings indicate that circular ring specimens failed under a combination of tensile and compressive stresses. The main crack originates along the loading direction on the inner wall of the ring and propagates outwards, resulting in the failure of the entire ring structure. While maximum tensile strain may serve as an indicator of rock failure, tensile stress alone should not be considered a definitive criterion for failure.