1. Senior Researcher, Korea Railroad Research Institute, Uiwang, Gyeonggi-do, KR, e-mail: geolsj@krri.re.kr
2. Research Professor, KAIST, Daejeon, KR (Corresponding author), e-mail: ywchoo@kaist.ac.kr
3. Principal Researcher, Korea Railroad Research Institute, Uiwang, Gyeonggi-do, KR, e-mail: jinugi@krri.re.kr
4. Principal Researcher, Korea Railroad Research Institute, Uiwang, Gyeonggi-do, KR, e-mail: rockcore@krri.re.kr