Developmet of Joint Element Considering Time-dependency

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At first, the comprehensive survey of previous publications on time-dependent behavior of rock was performed. Then, the creep and ralaxation tests were carried out under the uniaxial condition to obtain the fundamental properties of a sample rock paying special attention on visco-elasticity. After two testing methods, constant stress and constant strain methods, to obtain the time-dependent properties of joint was thoroughly compared and carefully examined, relaxation in direct shear tests were performed. It was revealed that shear stress decreases monotonously with elapsed time under the constant shear strain.A new joint element which represents the time-dependency was proposed on the basis of the previous publication and the obtained experimental results in this study. The special care was taken that the joint element was comfortable with the previous joint elements as far as possible. The joint element fundamentally consists of springs of which compliance increases with time. Finally, we implemented the joint model onto a computer program of finite element method.