The effect of jaw's curvature on Brazilian tensile strength of rocks

This paper investigates the effect of the jaw's curvature, also known by contact angle and jaw arc central angle (2α), of the Brazilian test apparatus on indirect tensile strength of various rock types. That's why, ten rock samples including limestone, marble, skarn, granite, diorite, and granodiorite were collected from some quarries in different provinces of Iran. Petrographic, mineralogical and textural investigations were performed using thin section analyses. Physical properties of the selected rock samples namely dry and saturated unit weights, porosity, water absorption, and specific gravity were determined for the rock samples. In addition, Brazilian tensile strength at different 2α angles (i.e., 2α = 0° , 10° , 15° , 20° , 45° , and 60° ) were determined for the rocks in the laboratory. Results show that the parameter for the rocks is between 3.81 MPa at 2α=0° and 54.76 MPa at 2α=60° . This means that Brazilian tensile strength increased with increasing 2α angle from 0° to 60° . Also, it was found that the highest change rate of the Brazilian tensile strength occurs in range of 2α=15° −30° for most studied rock samples. In some tested samples, the parameter is decreased only at 2α = 60° . The values of Brazilian tensile strength of the rocks tested by flat and standard jaws are near to each other.