1. Ph.D. Candidate, State Key Hydraulics Laboratory, Sichuan Univ., Chengdu, Sichuan 610065, China.
2. Professor, State Key Hydraulics Laboratory, Sichuan Univ., Chengdu, Sichuan 610065, China.
3. Professor, Dept. of Civil Engineering, Univ. of Birmingham, Birmingham B15 2TT, U.K.