1. Dept. of Civil Engineering, Univ. Of Cape Town, Private Bag X3, Rondebosch, 7701, Cape Town, ZA, e-mail: kptden001@myuct.ac.za
2. Inst. for Geotechnical Engineering (IGS), Univ. of Stuttgart, Institute for Geotechnical Engineering (IGS), Pfaffenwaldring 35, 70569 Stuttgart, DE, e-mail: Johannes.Aschrafi@cdmsmith.com
3. Dept. of Civil Engineering, Univ. Of Cape Town, Private Bag X3, Rondebosch, 7701, Cape Town, ZA, (Corresponding author)e-mail: denis.kalumba@uct.co.za
4. Inst. for Geotechnical Engineering (IGS), Univ. of Stuttgart, Institute for Geotechnical Engineering (IGS), Pfaffenwaldring 35, 70569 Stuttgart, DE, e-mail: Julian.Lehn@igs.uni-stuttgatt.de
5. Inst. for Geotechnical Engineering (IGS), Univ. of Stuttgart, Institute for Geotechnical Engineering (IGS), Pfaffenwaldring 35, 70569 Stuttgart, DE
6. Maccaferri SA Ltd, 227 Trademark Ave. P.O Box 2285, 2162 Johannesburg, ZA