Negative Skin Friction Due to Wetting of Unsaturated Soilby Richard C. Hepworth,
Abstract: A steel building at a cement plant un Utah was originally supported by spread footings. Shallow wetting of the coarse granular soils supporting the footings resulted in over three inches of settlement. Piles were used to underpin the building. The northeast corner column was supported by two 12 × 54 WF piles driven to depth 98 feet. About two years after the underpinning a deep wetting of the soils at the northeast corner occurred. The result was several inches of additional settlement on this corner of the building and twelve inches of ground subsidence adjacent to it. Excavation around the pile cap revealed that one of the piles was eight inches below the pile cap. A pull out test performed on the failed pile indicated the skin friction force was at least 182 tons. The building corner was underpinned again with three BP 12 × 74 piles driven to depth 145 feet. The upper 50 feet of each new pile was sleeved with an outer casing. Performance has been satisfactory since.
Subject Headings: Unsaturated soils | Skin friction | Soil settlement | Underpinning | Granular soils | Footings | Excavation | Driven piles | Land subsidence | Utah | North America | United States
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