Replacement of a Failed Embankment Designed to Accommodate Large Settlement: A Case Study

by B. Kent Merritt, (F.ASCE), Geotest Engineering, Inc, Houston, United States,
Gary M. Wantland, (M.ASCE), Geotest Engineering, Inc, Houston, United States,

Document Type: Proceeding Paper

Part of: Vertical and Horizontal Deformations of Foundations and Embankments


Thick deposits of soft, normally to slightly preconsolidated, organic clay are common at low elevations along the riverbanks of southeast Texas. Both the moisture content and liquid limit of these organic clays often exceed 250 percent, with organic contents as large as 50 percent. Undrained shear strengths typically range from 2 to 15 kPa. Construction of lightly loaded structures on these soils is possible because of a desiccated crust, generally from 0.3 to 1 m thick. These soft clay deposits are often the site of the effluent basins for nearby petroleum process plants. In 1979, the levee impounding one such basin failed during reconstruction. Large lateral and smaller vertical deformations were associated with the failure, reducing the shear strength of the organic clay foundation. This reduction in shear strength precluded reconstruction of an earthen levee to the required elevation. The integrity of the waste impoundment was reestablished with a two-stage design and construction sequence. The first stage was designed to stop further lateral movement and provide a stable base for continued construction. The second stage consisted of a `flexible' wall of precast concrete boxes over a high modulus geotextile. The boxes were connected in such a way that differential vertical movement could occur between adjacent boxes. The concrete wall was `light' when compared to an equivalent earthen levee, thus mobilizing acceptable shear stresses in the organic clay foundation.

Subject Headings: Soil settlement | Shear strength | Clays | Soil water | Soil strength | Soil deformation | Soft soils | Texas | United States

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