Much research has been carried out on the time-dependent behavior of rocks. It is well known that uni axial compressive strength increases as the strain rate becomes larger. Rock in general mainly contains microscopic cracks. In process to failure, cracks seem to develop parallel to the loading direction from the tip of microscopic cracks. Therefore, it is important to pay attention to the behavior of the circumferential strain when the time-dependency of stress-strain characteristics of rocks is examined. In this study the uni axial compression test are carried out using tuff , and the effect of stress rate on the stress-strain behavior is described.
There is little research on the mechanical characteristics of rock under tensile stress compared with the research on compressive stress. In this study, firstly, direction, length and number of micro cracks were investigated using Inada granite.Secondly, the uniaxial tension test is carried out with the specimen produced in a different direction, an anisotropy of uniaxtial tensile strength, Young's modulus and Poisson's ratio are investigated. In addition, to focus on the effective sectional area of the specimen, considered results on anisotropy of Young's modulus and uniaxial tensile strength were described.
In this study, the diametrical compression test was carried out using Inada granite by attaching strain gages to the test specimen.Young's modulus under tensile stress was estimated from the value of the measurement of the strain. The results obtained through this study are as follows:1) It is deemed that Young's modulus under tensile stress can be estimated from the diametrical compression test results by the method shown in this research.2) The standard deviation of tensile strain was calculated. The results showed that standard deviation increases rapidly, once the tensile stress exceeds a certain value. It is considered that the stress of a tensile fracture area differs within a test specimen if the load increases. Therefore, if tensile strength estimates from St=-2P/πDL use maximum load, it is possible that tensile strength was overestimated.
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