Evaluation of Gardiner Dam's ongoing movement
Gardiner Dam is located on the South Saskatchewan River approximately 100 km south of Saskatoon, SK. After the start of construction, the River Embankment experienced downstream movement in the shale portion of the foundation. Observed movements are occurring on a well-defined shear plane within the shale layer. This continuing foundation deformation raises concerns regarding the long-term stability of the structure and the effect of continuing deformation on the integrity of the embankment and ancillary works. The mechanism(s) responsible for the ongoing movements are not fully understood. As such, prediction of on-going deformation has had only a limited success. In the work presented in this dissertation, historic geotechnical instrumentation data was used to identify a potential mechanism of movement within the shale foundation. The potential mechanism thus identified can be briefly described as a combination of elastic deformation and consolidation within the shale. As the reservoir level rises, part of the increase in horizontal thrust is transferred to the shale. Since the shale is relatively stiff and has a low hydraulic conductivity, the increase in loading is; therefore, transferred to the porewater, resulting in generation of excess porewater pressures in shale. When the reservoir is high a portion of the excess porewater pressure dissipates. The observed horizontal movement along the shear zone is then developed from elastic deformation and horizontal consolidation of the shale from dissipation of excess porewater pressure. An analytical model was developed from the proposed conceptual model and had general success predicting the horizontal displacement based on the reservoir level and time period. However, the model was sensitive to the reservoir level and several variables within the shale including the hydraulic conductivity and porewater parameter B. Overall, the material variables such as hydraulic conductivity and B can be refined; however, without having an accurate reservoir prediction into the future, the ability for this model to predict the displacement in the foundation will be limited.
Gardiner Dam, Deformation, Marine Shale, Reservoir Cycle, Saskatchewan
Master of Science (M.Sc.)
Civil and Geological Engineering