1. Sr. Engr., BG Technol., Gas Res. and Technol. Ctr., Ashby Rd., Loughborough, Leicestershire LE11 3GR, U.K. E-mail: ed.faragher@ bgtechology.com
2. Lect. in Geotechnics, Dept. of Civ. and Build. Engrg., Loughborough Univ., Loughborough, Leicestershire LE11 3TU, U.K.
3. Prof. of Geotech. Engrg., School of Civ. Engrg., Univ. of Birmingham, Birmingham B15 2TT, U.K.