The pull-off test (POT) is a traditional method for tensile strength testing of concrete and building material. Recently, the method was used to obtain the tensile strength of rocks and geological discontinuities and was compared with the traditional tensile tests used in rock engineering. This paper discusses important aspects affecting pull-off tests in rocks and geological discontinuities, including the choice of POT device, adhesive types, adhesive lateral reinforcement, metal disc material and thickness, partial core depths and failure modes. POTs of high tensile strength rocks require an adhesive lateral reinforcement to avoid invalid failures (adhesive-rock interface). Valid failure modes occur along the core base peripheries or along geological discontinuity and lithological contact planes. The POT results are close to the direct tension test (DTT) results, and the correlation between these tests and the uniaxial compressive test (UCT) are similar, thus the POT is a practical alternative for estimating the direct tensile strength of rock material.
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