Seismic Design of a motorway embankment on improved ground: a performance based design approach

A motorway embankment build on soft peaty soil, which has been improved by vibroreplacement (stone columns) and preloading is examined with respect to its seismic performance. For the assessment of the amount of coseismic permanent displacements, simple sliding block methods are compared with more complex two dimensional dynamic analyses, performed by a finite difference code (FLAC). The embankment deformation is calculated for two action levels in order to provide the basis for assessment of embankment performance. It is suggested that the performance criteria of such embankments is not always rational to relate to a single displacement parameter. Motorway pavement serviceability and damage is more directly related to extensional deformation and angular distortion of embankment crest. For this reason the acceptable displacements (as a single parameter), is difficult to set in a rational manner.