Chasing a complete understanding of the failure mechanisms and potential hazards of the slow moving Liangshuijing landslide

Abstract

Landslides in the vicinity of reservoirs are prone to generate deadly waves as in the infamous Vajont case. There are more than 3800 landslides in the Three Gorges Reservoir area through detailed geological investigations, which constitutes a serious tsunami threat to the population and properties nearby. The Liangshuijing landslide, a very large creeping landslide located in the region and characterized by a complex morphology of multiple time varying failure mechanisms, is here investigated. Currently comprehensive measurements taken by ground monitoring network, inclinometric readings, in situ and laboratory geotechnical tests were analyzed to build a conceptual model for the landslide's drivers and its kinematics. The cumulative displacement time series were decomposed into trend and periodic components to reliably establish the relationship between displacements and reservoir behavior. A series of numerical slope stability analyses employing finite element limit analysis was performed to identify the material properties compatible with the observed landslide kinematics. Our results shed light on how reservoir behaviors drive landslide development, on how the identified failure mechanisms affect the observed terrain displacements and on which failure mechanism turns out to be dominant as reservoir conditions change. Our findings provide new insight for hazard assessment and mitigation of landslides near reservoirs: considerably smaller local failure mechanisms may cause a tsunami almost severe. Therefore, a single stability analysis may not be adequate but a full suite of analyses probing the range of possible conditions is required.