UBC Theses and Dissertations

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UBC Theses and Dissertations

Analysis of piezometer measurements and stratigraphy at Sugar Lake Dam Desjarlais, Christian


Piezometric measurements in the right abutment of Sugar Lake Dam read higher than the reservoir level and fluctuate seasonally with the operation of the reservoir. This thesis examines the influence of abutment geometry, stratigraphy, reservoir operation, and regional groundwater on the piezometric readings within the abutment. To complete this, a thorough review of the regional bedrock and glacial geology was completed, as well as of the right abutment geology and construction history. Field work consisted of site investigations on foot and by use of a UAV. UAV data was processed in Pix4D and ADAM 3DM software where photogrammetric methods produced orthophotos, digital elevation models, and joint set mapping. Statistical analyses of historical piezometer measurements were conducted with the open-source software R. Time series decompositions, cross-correlation analysis, spectral decomposition, and Fourier coupled ARIMA modelling were completed. A 3-dimensional finite element seepage model, created within the Rocscience software RS3, was used to validate the physical assumptions of the inter-abutment relationships. The model geometry was created using the photogrammetry outputs and supplemented with LiDAR data. Borehole logs were also used to guide the construction of the subsurface geometry. Results of the statistical and finite element modelling demonstrated that the regional groundwater levels are the driver for the elevated piezometer readings while the reservoir dominates the fluctuations. This is made possible by the stratigraphy of the abutment and the geometry of the dam and its appurtenant structures.

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