Failure in anisotropic sensitive clays: a finite element study of the Perniö failure test

The railway network on coastal areas of Finland is predominantly located in soft clay areas. The undrained shear strength of such clays is generally low, highly anisotropic, rate dependent and it exhibits post-peak strain softening under undrained conditions. A full-scale failure test was performed by Tampere University of Technology in Perniö, Western Finland, in 2009. A shallow railway embankment built on a soft clay deposit was equipped with a loading structure and loaded to failure in about 30 hours. The embankment collapsed two hours after the last loading step. In this study, data collected from the experiment is used, together with laboratory test results on high quality samples, to conduct advanced finite element analysis of the Perniö failure test. The NGI-ADPSoft model is used for this purpose, which is capable of simulating the strain-softening behavior of the clay. Even though the observed rate effect is not taken into account in the analyses, the failure load can be predicted reasonably well. Good agreement is also observed for calculated displacements and failure mechanism with experimental observations.