Application of geophysical methods in a dam project: Life cycle perspective and Taiwan experience Chun-Hun Lin a , Chih-Ping Lin b, ⁎, Yin-Chun Hung c , Chih-Chung Chung d , Po-Lin Wu b , Hsin-Chan Liu b a Department of Marine Environment and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan b Department of Civil engineering, National Chiao Tung University, Hsinchu, Taiwan c Department of Urban Planning and Landscape, National Quemoy University, Kinmen, Taiwan d Department of Civil Engineering, National Central University, Zhongli, Taiwan abstract article info Article history: Received 28 March 2018 Received in revised form 27 July 2018 Accepted 27 July 2018 Available online 29 July 2018 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 dur- ing feasibility investigation phase is already part of the standard of practice. This paper introduces newer appli- cations 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 dam, 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 surveil- lance and engineering significance at all stages. © 2018 Elsevier B.V. All rights reserved. Keywords: Dam safety Engineering geophysics TDR ERT Surface wave Seismic tomography 1. Introduction With growing population and higher demand for clean water, the number of dams has increased considerably during the last century. In addition to the number of dams, increased heights and larger reservoir volume are common around the world. The purpose of a dam is to retain water for societal benefits such as: flood control, irrigation, water supply, energy generation, recreation, and pollution control. A great percentage of dams are located near densely populated areas. Although many benefits are gained from dams, the potential threats to public safety and welfare cannot be ignored. The failures of Spain's Puentes Dam in 1802, the U.S. Teton Dam in 1976, and Brazil's Germano mine tailing dam in 2015 represent examples of the life threatening conse- quences resulting from unexpected or unrecognized dangers associated with dams, as well as serve as a reminder of the importance of a robust dam safety program. These high-profile failures resulted in stricter, more prescriptive, regulatory procedures to better ensure safety during the dam's service life. A dam project can be divided into three phases: feasibility and planning (Phase I), construction (Phase II), and operation (Phase III). For each phase, conceptual failure modes and risk assessment have been developed. Site investigation during feasibility and planning study, quality control/assurance during construction, monitoring programs and regular safety evaluation during operation have been standardized to ensure public safety against risk of dam fail- ure. Nonetheless, engineering geophysics can supplement these safe- guards by enhancing the technical and economical effectiveness of the resource management and safety throughout a dam's life cycle. Application of engineering geophysics for Phase I site characteriza- tion was recognized as early as 1928, when I.B. Crosby and E.G. Leonardon used electrical methods to map high-resistivity bedrock for a proposed dam site (Burger et al., 2006). Since then, geophysical methods have become part of the investigation program for potential dam sites. Further growing of geophysical applications on dam mainly focuses on the Phase III after the dam is completed. Typical dam safety surveillance uses visual inspection, along with limited support from geotechnical measurements. However, dams are massive structures and their internal hydraulic conditions may require attention before problems are detected by simple reconnaissance methods. Visual in- spections do not provide information inside the dam, while the discrete monitoring instruments provide engineering parameters with limited spatial coverage of the dam. There is a growing demand for non-de- structive geophysical techniques to internally image the dam for early detection of anomalous phenomena and facilitating remedial actions Journal of Applied Geophysics 158 (2018) 82–92 ⁎ Corresponding author. E-mail address: cplin@mail.nctu.edu.tw (C.-P. Lin). https://doi.org/10.1016/j.jappgeo.2018.07.012 0926-9851/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Applied Geophysics journal homepage: www.elsevier.com/locate/jappgeo