Abstract
To correctly obtain the spatial stress distribution and failure process of disc specimen in the Brazilian splitting test, an analytical solution of three-dimensional stress is deduced. Then, the effects of height-diameter ratio and clamp radian on the spatial stress distribution and failure process are analyzed and studied combined with numerical modelling. At last, the influence of spatial effect on the tensile strength of disc specimen is discussed. The results show that the cracks firstly generate at the two ends of the specimen in the axial direction and then extend due to the nonuniform distribution of tensile stress. The macrocracks coalescence does not mean the capacity loss of radial bearing. The maximum radial bearing capacity of the disc specimen decreases with the increase of height-diameter ratio due to the spatial effect. The tensile strength obtained by the two-dimensional calculation formula is significantly smaller. Therefore, when the commonly-used height-diameter ratio of 0.5 is used in the Brazilian splitting test, a correction factor k = 1.15 − 1.25 is suggested.
Highlights
The tensile strength of a rock is the ability of a rock specimen to resist damage under uniaxial tension, or ultimate strength, which is equal to the maximum tensile stress at failure in value
The results show that the maximum tensile stress at the two ends of the disc exceeds 10% of the center point when the height-diameter ratio is greater than 0.5
For the commonly used height-diameter ratio of 0.5-1.0, the tensile strength of the three-dimensional disc calculated with the maximum loading is 0.82 times of the value calculated by Eq (10)
Summary
The tensile strength of a rock is the ability of a rock specimen to resist damage under uniaxial tension, or ultimate strength, which is equal to the maximum tensile stress at failure in value. The main factors affecting Brazil’s tensile strength formula are (1) the influence of stress space: Brazil’s test is based on the analytical solution of plane elasticity stress, but it is in a three-dimensional stress state. The problem with the Brazilian test method is that the formula for calculating the tensile strength comes from the elasticity analytical solution of the plane stress problem, while the force on the sample in the actual test is a threedimensional mechanical problem. It is very necessary to use the three-dimensional elastic theory to derive the three-dimensional stress distribution law of the Brazilian test, but only a small number of scholars are conducting exploratory research in this area This fundamental subject can be studied with the aid of modern threedimensional finite element mechanical analysis. The influence of spatial effect on the tensile strength of disc specimen is discussed, and a correction factor k in the Brazilian splitting test is given
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