Browsing by Author "Hung, Yin-Chun"

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3D and Boundary Effects on 2D Electrical Resistivity Tomography
(2019-08-01)
Hung, Yin-Chun
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Lin, Chih-Ping
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Lee, Chin-Tan
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Weng, Ko-Wei
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土木工程學系
Electrical resistivity tomography (ERT) is one of the most widely used geophysical methods in geological, hydrogeological, and geo-environmental investigations. Although 3D ERT is now available, 2D ERT remains state-of-the-practice due to its simplicity in fieldwork and lower space requirements. 2D ERT assumes that the ground condition is perpendicular to the survey line and outside the survey line is homogeneous. This assumption can often be violated in conditions such as geologic strikes not perpendicular to the survey line and topographic changes or buried objects near the survey line. Possible errors or artifacts in the 2D resistivity tomogram arising from violating the 2D assumption are often overlooked. This study aimed to numerically investigate the boundary effects on 2D ERT under various simplified conditions. Potential factors including resistivity contrast, depth and size of buried objects, and electrode spacing were considered for the parametric studies. The results revealed that offline geologic features may project onto the 2D tomogram to some extent, depending on the aforementioned factors. The mechanism and implications of boundary effects can be drawn from these parametric studies.
Application of geophysical methods in a dam project: Life cycle perspective and Taiwan experience
(2018-11-01)
Lin, Chun-Hun
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Lin, Chih-Ping
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Hung, Yin-Chun
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Chung, Chih-Chung
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Wu, Po-Lin
There is a growing demand for using non-destructive geophysical techniques to internally image dam condition and facilitate the early detection of anomalous phenomena. Near surface geophysical techniques have advanced significantly in the last few decades, and can play a significant role in the siting, construction, and operational safety and sustainable management of dams. Application of engineering geophysics in site characterization during feasibility investigation phase is already part of the standard of practice. This paper introduces newer applications of engineering geophysics during construction phase, dam safety assessment, and sustainable management, including quality control of compacted soils, investigation of abnormal leakage in an earth darn, evaluation of an aged concrete dam, geophysical health monitoring for a newly-constructed dam, and monitoring of sediment transport for sediment management. The applications were presented with more emphases on the needs of dam engineering and adapting appropriate geophysical methods to make assessment more effective and consequential. The collage of these case studies is to broaden the view of how geophysical methods can be applied to a dam project throughout a dam's life cycle and strengthen the linkage between geophysical surveillance and engineering significance at all stages. (C) 2018 Elsevier B.V. All rights reserved.
Performance of 2-D ERT in Investigation of Abnormal Seepage: A Case Study at the Hsin-Shan Earth Dam in Taiwan
(2014-06-01)
Lin, Chih-Ping
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Hung, Yin-Chun
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Wu, Po-Lin
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Yu, Zen-Hung
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交大名義發表
There is a great demand for effective non-destructive methods to examine the interior of reservoir structures, such as dams. The present study was aimed at assessing the performance of electrical resistivity tomography (ERT), a popular non-destructive testing method, to investigate leakage at an earthen dam. Several abnormal leaks appeared on the downstream face after the dam was reconstructed to raise the maximum reservoir water level. Three 2-D ERT surveys were deployed on the left abutment, dam crest, and downstream shell. Periodic measurements were also collected on the downstream shell for time-lapse measurements. To gain confidence and avoid over interpretation, the 3-D effects on 2-D ERT were examined and the results of the 2-D ERT were appraised by forward modeling and synthetic inversion. Integration of ERT results with geotechnical monitoring data revealed the likely mechanism of abnormal seepage. Relational interpretation of time-lapse measurements further supported the hypothesized mechanism. By considering possible 3-D effects, the use of time-lapse measurements, and integration with geotechnical monitoring data, this case study provided new engineering perspectives on how 2-D ERT can be effectively used for seepage investigation.