The design and construction of underground openings, supports and rock pillars, as well as drilling and blasting, are based on an understanding of the mechanical behaviour of rocks under various loading conditions. The Brazilian indirect tensile tests described in the paper were carried out on Brisbane tuff, a host rock of Brisbane's first motorway tunnel, from which core samples were obtained. Three different types of cyclic loading were used in this research. The main purpose of performing the three types of cyclic loading was to find the most damaging cyclic loading type. The indirect tensile strength of Brisbane tuff was reduced from the static value of 10.8 to 7MPa as a result of Type I cyclic loading. Comparing the results of the sinusoidal, Type I and II cyclic loading tests, the maximum BITS reduction was obtained with the highest amplitude in Type I and smallest amplitude Type II cyclic loadings.
The study of brittle fracture and its relationship to material damage, fatigue and strength is central to many rock engineering problems, including rock fracture and damage mechanics, rock cutting, drilling and blasting techniques for the design and construction of underground openings, supports and rock pillars. Mechanical behavior of rock under static loading has been thoroughly investigated. However, rock reaction to cyclic, repetitive stresses resulting from dynamic loads has been generally neglected, with the exception of a few rather limited studies (Attewell & Farmer 1973, Bagde & Pedros 2005, Costin & Holcomb 1981, Evans & Fuller 1974, Haimson & Kim 1971, Haimson 1978, Tao & Mo 1990). The tensile strength of rock is one of the most important parameters influencing its deformability and fracture toughness. An impressive outcome of this study is the observation of the effect of tensile cyclic loading on the indirect tensile strength (ITS). The difficulties associated with performing a direct uniaxial tensile test on a rock specimen have led to a number of indirect methods for assessing tensile strength. In 1978, the Brazilian test was officially proposed by the International Society for Rock Mechanics (ISRM) as a suggested method for determining the tensile strength of rock materials (ISRM 1978).
