Engineering Properties of Badlands in Semi-Arid Regions
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Abstract
Geology and seasonal weather variations govern the engineering properties of Avonlea badlands in Saskatchewan, Canada. Three surface sediments exhibiting distinct lithologic variations were found: a steep and fissured sandstone; a mildly-sloped and popcorntextured mudrock; and a flat and eroded pediment. The variation in material composition and the water availability conditions increase the saturation-desaturation cycle that ultimately affect material behavior. The fines content increased from dry to wet state with 17% to 33% for sandstone, 4% to 98% for mudrock, and 21% to 42% for pediment. The water adsorption capacity was found to be highest for mudrock (wl = 96% and wp = 47%) followed by sandstone (wl = 39% and wp = 31%) and then by pediment (wl = 31% and wp= 23%). The SWCC of sandstone and mudrock showed bimodal distributions with a low AEV (6 kPa and 9 kPa) pertaining to drainage through cracks and a high AEV (160 kPa and 92 kPa) associated with flow through the soil matrix. The pediment followed a unimodal SWCC with a single matrix AEV of 4 kPa. The saturated hydraulic conductivity for sandstone, mudrock and pediment measured 8.5 x 10-6 m/sec, 4.0 x 10-8 m/sec, and 1.8 x 10-5 m/sec respectively. XRD analyses indicated that the major clay minerals present were 14% illite (micaceous clay) in sandstone, 2.3% smectite, 7% kaolinite and 3.1% illite in mudrock while 3.8% illite in pediment. Mudrock was identified as the severe swelling potential badland sediment if desiccated. Overall, the swelling potential observed for sandstone, mudrock and pediment was approximately 19%, 102%, and 2% respectively.