Description and Analysis of geotechnical aspects associated to the large 2010 Chile earthquake

Abstract

A description of the strong 27 February 2010 seismic event occurred in centre and south of Chile is presented. Main geology and geotechnical conditions of selected sites are described. The study focuses mainly, but not only, on the liquefaction phenomenon which affected housing developments in Concepción, Hualpén and San Pedro de la Paz. The earthquake occurred at the end of the summer; therefore ground dry conditions prevailed. However, grounds near to water bodies were still saturated, mainly in places which were previously part of swamps and wetlands. In some of these places the replacement of soft and loose soils for compacted sand fills was not enough to avoid the occurrence of liquefaction. It is suggested to consider other techniques of soil improvement or deeper foundations when the subsoil has low shear strength and hence potentially liquefiable. An example of dynamic compaction for a 1998 housing development project in Concepción, which performed successfully during this earthquake, is described. Failures in the Coihueco earth dam and in Las Palmas tailing dam are analysed. The former suffered cracks on the crest and a downward movement of a part of the upstream shoulder. The latter collapsed completely due to widespread liquefaction leading to the flow of material downstream. Landslides of cliffs in the coast of Arauco and failures of bridges and embankments resting on soft soils are also analysed. Cliffs formed of marine sandstones and siltstones are believed to slide due to not only the strong seismic shaking but also due to large horizontal and vertical displacements experienced by the Arauco Peninsula. Finally, it is suggested to carry out further research to study in more detail these preliminary findings.