Collapse Mechanism of Compacted Clayey and Silty Sands

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by T. A. Alwail, Ministry of Petroleum, Riyadh, Saudi Arabia,
C. L. Ho, (M.ASCE), Ministry of Petroleum, Riyadh, Saudi Arabia,
R. J. Fragaszy, (M.ASCE), Ministry of Petroleum, Riyadh, Saudi Arabia,

Document Type: Proceeding Paper

Part of: Vertical and Horizontal Deformations of Foundations and Embankments:

Abstract: The mechanism of wetting-induced collapse (hydrocompression) and the influence of fines ratios on compacted sandy soils are investigated. Various ratios of clay and silt are mixed with Ottawa sand to produce twenty-five soil combinations. Each soil is examined qualitatively under the Scanning Electron Microscope before and after collapse. Observed fabric alterations are supported by data obtained from Double-Oedometer Tests. Clay structures before collapse transform to a continuous or discontinuous clay blanket after collapse, depending on the initial clay quantity present in the soil. Magnitude of collapse increases with increasing clay/silt ratios. Silty sands with sharp silt grains and/or a higher clay content demonstrate greater collapse than soils with rounded silt grains and/or less clay content. This study suggests that collapse is profoundly influenced by the quantity of clay and the interaction of percolating water and the clay fractions of soils. A model showing fabric alterations of compacted clayey sands, silty sands, and clayey silty sands is presented.

Subject Headings: Clays | Compacted soils | Silt | Structural failures | Soil mixing | Sandy soils | Collapsible soils | Soil water |

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