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