• 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.26 no.4
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• pp.447-460
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• 2016

Samples of Hangdeung granite and Berea sandstone containing sliding planes were prepared by saw-cutting and polishing using #100 or #600 grinding powders. Their basic friction angles were then measured directly in direct shear tests and triaxial compression tests, and also in tilt tests, which measure the angles indirectly. Although the angles measured by the direct methods were generally accurate, those measured along certain planes were greatly different from the others depending on the condition of the plane. The tilt tests yielded similar angles regardless of the sliding plane condition or the rock type; however, the error range was relatively wide. Sliding planes polished by the grinding powders yielded more accurate results than those cut by the saw and tested without polishing, as polishing ensured consistent conditions among all the planes. Sliding planes polished using #100 grinding powder yielded better results than polishing with #600 grinding powder. Therefore, the basic friction angles measured along the sliding planes polished using #100 grinding powder, as obtained in direct shear and triaxial compression tests, were the most reliable. The angle could also be measured satisfactorily by tilt testing along sliding planes polished with #100 grinding powder.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.2
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• pp.27-38
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• 2015

In this study, the 3D position coordinates were calculated for the targets using DLT and self-calibration bundle adjustment with additional parameters in close-range photogrammetry. And then, the accuracy of the results were analysed. For this purpose, the results of camera calibration and orientation parameters were calculated for each images by performing reference surveying using total station though the composition of experimental conditions attached numerous targets. To analyze the accuracy, 3D position coordinates were calculated for targets that has been identically selected and compared with the reference coordinates obtained from a total station. For the image coordinate measurement of the stereo images, we performed the ellipse fitting procedure for measuring the center point of the circular target. And then, the results were utilized for the image coordinate for targets. As a results from experiments, position coordinates calculated by the stereo images-based photogrammetry have resulted out the deviation of less than an average 4mm within the maximum error range of less than about 1cm. From this result, it is expected that the stereo images-based photogrammetry would be used to field of various close-range photogrammetry required for precise accuracy.

• The Journal of Engineering Geology
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• v.22 no.3
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• pp.309-321
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• 2012

Elastic constants were measured for 70 samples of transversely isotropic banded gneiss from the Onyang region. Anisotropic angles of samples are $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$. Exact values of $E_2$ and ${\nu}_{21}$ can be measured from samples with anisotropic angles of $0^{\circ}$ and those of $E_1$ and ${\nu}_{12}$ from samples with anisotropic angles of $90^{\circ}$. These values are set as reference values. Elastic constants measured from samples with anisotropic angles of $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$, using the methods proposed by Jang et al. (2001) and Park et al. (2008), are compared with the reference values to examine the effectiveness of the two methods. $E_1$ were measured correctly from samples with anisotropic angles of $60^{\circ}$ and $75^{\circ}$, and $E_2$ from samples with anisotropic angles of $15^{\circ}$ and $30^{\circ}$, when using the method suggested by Jang et al. (2001). $E_1$ were measured correctly from samples with anisotropic angles of $45^{\circ}$ and $60^{\circ}$, and $E_2$ from samples with anisotropic angles of $15^{\circ}$, $30^{\circ}$, and $60^{\circ}$, when using the method proposed by Park et al. (2008). The effectiveness of the two methods was determined by error rates between exact values and measured values. The effectiveness of the two methods was similar. However, the method suggested by Jang et al. (2001) may be more effective in measuring $E_1$, while the method suggested by Park et al. (2008) may be more effective in measuring $E_2$.