Experimental study of influence of crack filling on mechanical properties of Brazilian discs

Fissure is one of the most important factors affecting mechanical properties and failure modes of rocks. Based on experimental results, digital photographic technology and acoustic emission (AE) monitoring to investigate tensile strength and failure modes of intact, and containing different crack angles alpha single, different angles between rock bridge and crack gamma double filled and unfilled pre-existing fissures rock-like material Brazilian disc samples. The effects on final failure mechanisms of samples with the change of filling condition, alpha and gamma are also discussed. The results show that the tensile strength of single pre-existing fissure filled samples decreases firstly and then increases and finally decreases with the increase of alpha. The wing cracks initiate from the tip of the pre-fissure, and then cut-through, finally the samples show brittle destruction. The tensile strength of those samples containing two pre-existing fissures decreases firstly and then increases with the increase of gamma. The propagation and evolution of wing cracks initiated from two pre-existing fissures and far-field cracks lead to the the destruction of samples. The tensile strength of filled samples is higher than unfilled samples obviously, when the corresponding values of a and rare the same. Whether the pre-existing fissure filling has a great impact on the crack propagation time and the number of cracks. At the initial loading stage, the cumulative acoustic emission counts are relatively stable. When the surface of samples initiated cracks initially or the tensile strength increases to the peak, the acoustic emission activities become extremely active. When the corresponding values of alpha and gamma are the same, the fluctuation of acoustic emission counts of the filled samples is more violent than that of the unfilled.