Laboratory Determination of Direct Tensile Strength and Deformability of Intact Rocks

Abstract

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.

Water Saturation Induced Changes in the Indirect (Brazilian) Tensile Strength and the Failure Mode of Some Igneous Rock Materials

“…As an example, use of the dog-bone (or dumbbell) shaped rock specimens for effective holding is among various DTS testing methods. However, the dog-bone shaped specimens are not widely used as a result of impractical preparation details [4][5][6][7].…”

Determination of Direct Tensile Strength Values of Rock Materials by a New Test Method of Drilled Disc Tension

“…The invalid failure of adhesive part can be seen especially for high strength rock materials. Besides of the use of adhesives for loading core specimens, different DTS test methods like using dog-bone shaped rock specimens have been developed for effective holding, but they are not popular because of impractical specimen preparation works [1][2][3][4].…”

Drilled Core Specimen Testing Method for Determination of Tensile Strength Values of Rock Materials

“…The invalid failure of adhesive part can be many times seen especially for high strength rock materials. Besides of the use of adhesives for loading core specimens, different DTS test methods like using dog-bone shaped rock specimens have been developed for effective holding, but they are not popular because of impractical specimen preparation works [7][8][9].…”