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UBC Theses and Dissertations

Geotechnical characterization and stabilization of muskeg soils using the microbially induced calcite precipitation technique (MICP) Elmouchi, Ahmed


Muskeg is the landform that describes the organic terrain. Muskeg soils are widespread in Canada. They cover around 15% of the Canadian landscape. Their problematic nature is attributed to their high compressibility and low shear strength when subjected to loads due to their high initial void ratio and water content. This study aims to investigate the problematic nature of Muskeg soils and provide a solution for their stabilization. Water and organic contents of Muskeg soils are the two primary index properties, and they are easy and inexpensive to determine. Therefore, many studies in the literature correlate the other index and compressibility with these two simply measured properties. An extensive review of the literature was conducted, and new correlations to determine some index and compressibility properties as a function of the organic and water contents were presented. These new proposed correlations would help the design engineers provide reasonable estimations in the concept design phase for projects that deal with this soil. Extensive laboratory and field testing programs were conducted for Muskeg soil samples retrieved from Bolivar Park, Surrey, British Columbia, Canada, to determine their geotechnical properties. New correlations for determining the maximum shear modulus Gmax as a function of the undrained shear strength Su, measured from the electronic vane shear test, and ball net tip resistance qb-net, measured from the ball penetration test, were demonstrated. Moreover, new correlations for the undrained shear strength Su as a function of the cone tip resistance qnet, measured from the seismic cone penetration test (SCPTu), and ball net tip resistance qb-net, measured from the ball penetration test (BPT), were presented. The excessive settlement of Muskeg soil was treated through the environmentally-friendly technique, the Microbially Induced Calcite Precipitation MICP using the urease active bioslurry approach. The results showed a substantial improvement in the compressibility properties when the bioslurry concentration was 0.4, the bioslurry weight was 10%, and cementation solution volume equals twice the pores' volume. The second round of stabilization was conducted to achieve further improvement by coupling the bioslurry with sand as additives. Further improvement was achieved by adding 10% of sandy soils while keeping the bioslurry concentration at 0.4 Mole/Litre, the bioslurry weight at 10% and cementation solution volume the same as the pores' volume.

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