• The Journal of Engineering Geology
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• v.29 no.4
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• pp.565-578
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• 2019

Basic friction angles of Hwangdeung granite, Berea sandstone, Jeongsun marble, Hongcheon gneiss, Pungam shale and Eumseong sandy shale were measured by direct shear test, tilt test and pull test. Characteristics of basic friction angle and the accuracy of test methods were compared and the optimal method in measuring basic friction angle was suggested. Although basic friction angles might be measured accurately by direct shear test, the test apparatus is expensive and procedures are complicated. Tilt tests which is the suggested method for measuring basic friction angle by International Association for Rock Mechanics also provided similar basic friction angles measured by direct shear test. However, the error measured for the same rock type is higher than 7° and values by repeated measurements in one sample show different trends, such as increasing or decreasing or almost constant as measurements continued. The difference measured in one gneiss sample is higher 12°, indicating that tilt test may be not a reliable method for measuring basic friction angle. Not only pull test provided accurate and consistent results under low normal stresses, but also test apparatus is simple and inexpensive and procedure is not complicated, indicating that pull test may be the optimal method for measuring basic friction angle.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.323-336
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• 2011

The hydro-mechanical behavior of the Earth's crust is strongly dependent on the fractional volume and geometrical structure of effective pore spaces. This study aims to understand the characteristics of pores using electrical impedance. We measured the electric impedance of core samples (diameter, 38-50 mm; length, 70-100 mm) of three types of granite (Hwangdeung, Pocheon, and Yangsan) and two types of sandstone (Boryung and Berea) with different porosities and pore structures, after saturation with saline water of varying salinities. The results show that resistance decreases but capacitance increases with increasing salinity of the pore fluid. For a given salinity, the resistivity and formation factor are reduced with increasing porosity of the rocks, and the capacitance increases. Berea sandstone shows anisotropy in resistance, tortuosity, and cementation factor, with these factors being highest normal to bedding planes. This result indicates that the connectivity of pores is weakest normal to bedding. In conclusion, the electrical characteristics of the tested samples are related not only to their porosity but also to the pore geometry.