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Rock mass contains various discontinuities, such as faults, joints, and bedding planes. Among them, a joint is one of the most frequently encountered discontinuities in rock engineering applications. Generally, a joint exerts great influence on the mechanical and hydraulic behavior of rock mass, since it acts as a weak plane and as a fluid path in the rock mass. Therefore, an accurate understanding on joint characteristics is important in many projects. In-situ tests on joints are sometimes consumptive in terms of time and expenses so that the features are investigated by laboratory tests, providing fundamental properties for rock mass analyses. Although the behavior of a joint is affected by both mechanical and geometric conditions, the latter are often limited, since quantitative control on the conditions is quite complicated. In this study, artificial rock joints with various geometric conditions, i.e., joint roughness, were prepared in a quantitative manner and the hydromechanical characteristics were investigated by several laboratory experiments. Based on the results, a prediction model for hydraulic aperture was proposed in the form of ( e h / e m ) 3 = exp ( − 0.0462 c ) × ( 0.8864 ) J R C , which was a function of the mechanical aperture, joint roughness, and contact area. Relatively good agreement between the experimental results and predicted value indicated that the model is capable of estimating the hydraulic aperture properly.

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Brazilian test which also known as indirect tensile test is widely used to evaluate the tensile strength of rock. Discrete element method (DEM) together with finite element method (FEM) approach was used to investigate numerically the response of granite material under Brazilian test for indirect measurement of tensile strength of rocks. The calibration analysis performed in this study using the commercial software LS-DYNA. It has been attempted to calibrate the micro-parameters in bonded particle model of granite rock for numerical modelling. In hybrid DEM-FEM simulation, the rock specimen was modelled in DEM while the steel plates were simulated using FEM. This numerical analysis is compared to experimental data of Brazilian test. It shows that the combination of numerical methods simulation could reproduce the trends of experimentally observed stress-strain curve of granite rock under tensile loading. Besides that, the hybrid DEM-FEM simulation also shows the same failure mode of granite specimen. Comparison between experimental data and numerical analyses is presented and discussed.

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