1. Professor, Dept. of Civil and Environmental Engineering, Nagaoka Univ. of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan. E-mail: sugimo@vos.nagaokaut.ac.jp
2. Senior Engineer, TEAM Engineering Consulting and Management Co., Ltd., 151 TEAM Building, Nuanchan Rd., Klongkum, Buengkum, Bangkok 10230, Thailand. E-mail: aphichat_s@team.co.th
3. Chief Researcher, Tunnel Engineering Laboratory, Railway Technical Research Institute, 2-8-38 Hikari, Kokubunji, Tokyo 185-8540, Japan. E-mail: konishi@rtri.or.jp
4. Senior Researcher, Tunnel Engineering Laboratory, Railway Technical Research Institute, 2-8-38 Hikari, Kokubunji, Tokyo 185-8540, Japan. E-mail: sugar@rtri.or.jp