1. Graduated Student, Dept. of Structural Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy.
2. Professor of Geotechnical Engineering, Dept. of Structural Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133, Milano, Italy.
3. Professor of Foundation Engineering, Dept. of Structural Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133, Milano, Italy (corresponding author).