1. Associate Professor, Dept. of Geotechnical Engineering, School of Engineering of São Carlos-USP, 13566-970 São Carlos, SP-Brazil.
2. Engineer, Federal Univ. of Viçosa, 36570-001 Viçosa, MG-Brazil.
3. Professor, Dept. of Civil Engineering, Federal Univ. of Viçosa, 36570-001 Viçosa, MG-Brazil.
4. Associate Professor, Dept. of Civil Engineering, Federal Univ. of Viçosa, 36570-001 Viçosa, MG-Brazil.