COMPACTIVE PRESTRESS EFFECTS IN CLAYS

The load-deformation behavior of natural clays is strongly influenced by the geologic maximum past pressure. If such clays are excavated and manipulated before compaction, the geologic effect is largely lost. However, the compaction process establishes a new prestress value, and the ratio of this prestress to the effective normal stress in a compacted fill forms a new overconsolidation ratio (OCR). If the material and compactive prestress values are held constant constant in a moderately high embankment, the OCR values range from quite high at lesser depths to unity in lower embankment locations. Consequently, the nature of the shearing and compressibility responses varies considerably with position in the embankment. Laboratory studies have been conducted on both compacted shales and clays to demonstrate the empirical prediction of the prestress value and its relative effect on saturated compressibility and undrained shear behavior. The prestress varies with the nominal compaction pressure and its rate of application, as well as with the material and its water content. This value is predicted from the conventional oedometer test on the as-compacted material. When the compacted materials are soaked at a variety of confining pressures, which simulate differing embankment positions, the volume changes are highly dependent on the major compaction variables and the prestress. To achieve a homogeneous and predictable load-deformation response in major embankments, it is necessary to better understand and control to examine the compressibility behavior of a laboratory-compacted soil in the as-compacted and soaked condition. A highly plastic residual clay and a kneading type of compaction were used. To determine the as-compacted compressibility characteristics, the compacted samples were trimmed to appropriate size and incrementally loaded in the oedometer. Of particular interest was the value of compactive prestress. (Author)

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/trr/1983/945/945-009.pdf
• Record URL:
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• Supplemental Notes:
  • Publication of this paper sponsored by Committee on Earthwork Construction. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • DiBernardo, Albert
  • Lovell, C W
• Publication Date: 1983

Media Info

• Media Type: Print
• Features: Figures; References; Tables;
• Pagination: pp 51-58
• Monograph Title: Subgrade moisture: soil properties, foundations, tunnel reinforcement
• Serial:
  • Transportation Research Record
  • Issue Number: 945
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Clay; Compaction; Compressibility; Deformation; Prestressing; Shale; Shear stress; Undrained shear strength; Volume changes
• Uncontrolled Terms: Shearing
• Subject Areas: Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00389573
• Record Type: Publication
• ISBN: 0309036666
• Files: TRIS, TRB
• Created Date: Oct 30 1984 12:00AM