1. Professor, Dept. of Civil Engineering, Saga Univ., 1 Hongjo, Saga 840-8502, Japan. E-mail: chai@cc.saga-u.ac.jp
2. Director, Institute of Soft Ground Engineering, 4-1-52 Ohtakara, Saga 840-0811, Japan.
3. Chief Engineer, Shiwa Techno Co., Ltd., 1856-1 Kubotacho Tokuman, Saga 849-0201, Japan.