Geomechanical characterisation and dynamic numerical modelling of two anthropogenic fill slopes

In the last 22 years, four large (between approximately 1000 and 5000 m3) flowslides in anthropogenic fill materials have occurred in residential areas of the greater Wellington region, New Zealand. Such failures are relatively rare, given that there are over 1600 mapped fill bodies, formed between the early 1900s and present day within the region. Nonetheless, their performance under strong earthquake shaking has yet to be tested, given no strong ground motions (>0.15 g) have shaken the region since their construction. In this study, we used remote sensing techniques, borehole investigations, geotechnical testing and numerical modelling to investigate two fill bodies that are characteristic of those constructed across the Wellington region. This paper presents the results from the dynamic analysis of these two sites under strong earthquake shaking.