1. Professor of Geotechnical Engineering, Dept. of Civil and Building Engineering, Loughborough Univ., Loughborough LE11 3TU, UK (corresponding author).
2. Engineer, Wasteconsult International, Robert-Koch-Str. 48b, 30853 Langenhagen, Germany; formerly, Dept. of Civil and Building Engineering, Loughborough Univ., Loughbourough LE11 3TU, UK.
3. Lecturer, Lab. (3S-R) Polytech, Univ. Joseph Fourier, Grenoble 1 BP 53X, 38041 Grenoble Cedex 9, France.