Influence of load contact condition on rock tensile strength

Tensile strength is one of the most important mechanical properties of rock for design of subterranean engineering constructions. It is also a key parameter of rock for strength design, safety and stability analysis of rock structures. The Brazilian test is an essential method for testing tensile strength of rock, which is widely used in the geotechnical engineering and rock mechanics. There is a great difference, however, in the testing results of tensile strength due to different contact conditions. Numerical calculation of FEM and experimental investigations are used in the present research. The influence of loading condition and size of indenter on the tensile strength of rock has been investigated. The results obtained by numerical calculation and experiments show that tensile strength of rock will increase with the increase of indenter size. The difference of tensile strength produced by testing and numerical calculation will decrease when using smaller contact angle a or indenter diameter. Experimental results obtained with white marble specimen show that a stable tensile strength with higher precision can be achieved when the ratio of d/D is in the range of 0.024-0.040. It gives a reference to choosing reasonable size of indenter in Brazilian test. This method provides theoretical and experimental basis for testing tensile strength of rock accurately.