Experimental and numerical investigations of dyke failures involving soft materials

This paper presents the results of an experimental and numerical investigation on the collapse of dykes involving soft soils. Nine centrifuge tests were carried out to investigate the dyke-subsoil interaction. The tests consisted in placing a dyke made out of Speswhite clay or Baskarp sand on a subsoil. The dykes and the subsoils were alternatively changed to explore the different contrast in stiffness ranging from stiff dykes on soft subsoil to soft dykes on stiff subsoils. The small scale models were placed in the centrifuge and were progressively accelerated up to a maximum of 100 G. The recordings, which were then processed by Particle Image Velocimetry (PIV), offered an insight onto the deformation and failure mechanisms. The results showed that dykes placed on a stiff subsoil underwent brittle failures with the development of slip surfaces whereas the same dyke placed on a soft subsoil underwent large deformation which presented a serviceability issue. These tests were then modelled with the Material Point Method (MPM), which is a continuum-based method for numerical simulation dedicated for large deformation problems. Simple constitutive models were used for which the parameters could be estimated using state indices.The authors acknowledge the Dutch Ministry of Public Works (Rijkswaterstaat-WVL) and the HHNK Water Authority for commissioning and financing the centrifuge tests. They would also like to thank the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement PIAP-GA-2012-324522 and the Swiss National Science Foundation under grant agreement P1SKP2 158621 for additional funding for the analysis of the data and the numerical modelling