Volume 34, Issue 1 (January 2011)
Laboratory Determination of Direct Tensile Strength and Deformability of Intact Rocks
The direct tensile strength and deformability are determined from dog-bone shaped specimens of intact sandstone, limestone, and marble by using a compression-to-tension load converter. The device allows a measurement of the rock elastic modulus and Poisson’s ratio under uniaxial tensile and compressive stresses on the same specimen. A series of finite difference analyses is performed to obtain a suitable specimen configuration that provides unidirectional tensile stresses at the mid-section of the specimen. The results indicate that the direct tensile strengths are clearly lower than the Brazilian and ring tensile strengths. The elastic moduli and Poisson’s ratios under uniaxial tension are lower than those under uniaxial compression. The discrepancy probably relates to the amount and distribution of the pore spaces and micro-fissures and the bond strength of cementing materials. The porous and relatively poor-bonding sandstone shows a greater difference between the tensile and compressive elastic moduli and Poisson’s ratios compared to those of the dense and well-bonding marble and limestone.