| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 90 === In general, the shear strength of rock joint is affected by the normal force, the mechanical properties of intact rock, and the morphological feature of joint surface. Owing to the different sizes of rock joints, the shear strength of rock joint is also different. In this study, we investigate the influence of geometrical variation of rock joint on the shear strength.
In order to simulate the irregular rock joint, we use the LOM1015-PLUS system to produce the rapid prototype, and choose the mixture of gypsum and quartz powder as the joint material. We use Barton’s standard profiles of JRC=4~6 and JRC=18~20 and a nature profile of Nan-Gang sandstone to be our irregular joints. In geometrical variation, we choose the divided, enlarged, reduced, and repeated profiles as the joint model.
Based on the result of a serial of direct shear tests, we discuss the change of shear strength of rock joints of different specimen sizes by controlling the normal stresses. The following conclusions are drawn：(1) Not every shear strength of smaller divided specimen is higher than the larger one, while as a whole, the average shear strength of the smaller specimens is higher than that of the original profile； (2)When we enlarge the profile proportionally, there is no obvious tendency of change in shear strength at the same normal stress；(3)With increasing the specimen sizes with repeated profiles, the shear strength tends to reduce. When the profiles are smoother, this phenomenon becomes unobservable.
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