Multi-Dimensional Analysis of Large, Complex Slope Instability
Kalenchuk, Katherine Sarah
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Complex deformation processes observed in massive slow-moving, active, landslides are contributed to by topography, non-uniform shear surfaces, heterogeneous rockmass and shear zone strength characteristics, composite failure mechanisms and hydrogeology. This thesis provides a systematic means to account for geology, geomorphology and geomechanics when interpreting slope deformation processes. Significant contributions to the field of landslide geomechanics have been made by analyzing how spatially discriminated slope deformations are influenced by spatial variation of geological and geotechnical factors and temporal changes in piezometric levels. The Downie and Beauregard landslides are massive instabilities that have extensive histories of slope monitoring and observational assessment, and where detailed site investigations have been completed. A methodology has been developed for the interpretation of 3-dimensional shear zone geometries using spatial prediction algorithms complemented by sound engineering judgment. The applicability of this process to other spatial data, such as displacement or piezometric records and measurements of material properties is demonstrated. Composite landslide deformations have been analyzed for both Downie and Beauregard to characterize global slope behaviour and identify localized events. Furthermore, a new interpretation of landslide morphological regions at Downie is provided. The research presented in this thesis demonstrates the importance and value of 3-dimensional numerical modelling. A rigorous procedure to numerically simulate large landslides has been developed. This sophisticated method accounts for complex geometries, heterogeneous shear zone strength parameters, internal shears, interaction between discrete landslide zones and piezometric fluctuations. This advance in state-of-the-art landslide modelling provides an important tool for investigating dynamic landslide systems. Based on Downie and Beauregard field data numerical models have been calibrated to reproduce observed slope behaviour. The calibration process has provided insight on key factors controlling massive slope mechanics. Calibrated models are used to investigate how trigger scenarios may accelerate deformations at Downie and the effectiveness of a proposed slope drainage system at Beauregard. The ability to reproduce observed behaviour and forward test hypothesized changes to boundary conditions has valuable application in landslide hazard management. The capacity of decision makers to interpret large amounts of data, respond to rapid changes in a system and understand complex slope dynamics has been enhanced.