The splitting tensile strength test (STST) is popular as it is simpler than the uniaxial tensile strength test. In STST, the line load is ideally applied to the cylindrical specimen and linear elastic theory was assumed. However, this test method may not be suitable for soft rocks as the stiffness is too small to assume line loading and the possible involvement of localized shear failure near the loading points.
In order to identify the failure mechanism in STST on soft rocks, the width of the strip load, wsl was measured, and the failure pattern near the loading point was examined. As the result, it was shown that STST is not suitable to evaluate the tensile strength, st,of soft rocks.