Characterizing Physical and Hydrotechnical Properties of Sediments Surrounding Soap Hole Features Near Didsbury, Alberta, Canada
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2024-10-22
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Soap holes are discrete occurrences of fluidized sediments that have been reduced to zero effective stress resulting in quick conditions. These features can be detrimental to farming operations through evaporitic concentration of ions in surface sediments surrounding the features or by fatally trapping livestock. Currently, the sediment properties and subsurface conditions required to generate soap holes are relatively unknown. A site investigation conducted near Didsbury, Alberta, analyzed the geologic, hydrogeologic and geotechnical conditions surrounding four active soap hole features to improve the understanding of soap hole formation. Glacially derived surface sediments and Paskapoo formation bedrock were extensively analyzed using a combination electrical resistivity tomography (ERT), cone penetration testing (CPT), and sediment coring and sampling. Laboratory analyses were completed on recovered sediment samples to determine index properties, particle-size distribution, Atterberg consistency limits, dispersive properties and chemical composition. ERT transects indicated there are three distinct sedimentary units on-site, and bedrock depth of approximately 11-mbgs, which was confirmed by drilling. Near-surface sediments are primarily comprised of non-sensitive, over-consolidated fine-grained material, with medium to high plasticity, and are highly dispersive. Discontinuous coarse-grains sediments were also noted in the sediment core, potentially providing flow-paths through the extensive fine-grained sediments. Hydrogeologic conditions were analyzed utilizing pressure transducer data, manual water level measurements, CPT correlations, and single well response tests. Artesian conditions were confirmed within a soap hole feature that was instrumented on site and are suspected to persist in the surrounding features. Pore pressures within and below the instrumented feature correlate with regional potentiometric surface maps of the Paskapoo formation, suggesting hydraulic connection to deep groundwater flow-paths. Strong upward vertical gradients (>1-m/m) within the soap hole feature exceed the critical gradient of surrounding sediments. Downward vertical gradients less than critical were found in most background sediments surrounding the features. Overall, sediments at the study site did not have properties indicative of being prone to liquefication. However, results suggest that high pore pressures, dispersive soils and vertical hydraulic gradients exceeding sediment critical gradients are some of the primary formation mechanisms of the soap hole features.
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Cunningham, D. Z. (2024). Characterizing physical and hydrotechnical properties of sediments surrounding soap hole features near Didsbury, Alberta, Canada (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.