1. Assistant Professor, Civil Engineering Dept., Cairo Univ., Giza, Egypt.
2. Assistant Professor, Dept. of Civil Engineering, Univ. of Waterloo, Waterloo ON, Canada N2L 3G1 (corresponding author).
3. Professor, Earth Sciences Dept., and Vice-Director, Porous Media Research Institute, Univ. of Waterloo, Waterloo ON, Canada N2L 3G1.