SPECIFICATIONS FOR BACKFILL OF REINFORCED-EARTH RETAINING WALLS
Compaction and construction control of certain fills used for the structural cross-section of mechanically stabilized earth (MSE) retaining walls can present significant problems in design and quality assurance. Locally available soil types, in particular fine sands, are difficult to compact easily with standard equipment and often give unrealistically low densities in standard compaction tests. This results in inappropriate specifications that do not produce adequate material properties in the field. The resulting variability of material properties can result in a number of problems, including undesirable differential settlements. A significant program of laboratory testing was undertaken to investigate these problems, including performing three different types of laboratory compaction methods on a total of 62 cohesionless sands. The standard Proctor test method gave low values of maximum dry density in almost all cases, while the modified Proctor test did so mainly for sands of coefficient of uniformity below about 3.5. The vibrating hammer test method gave significantly higher values of dry density over the complete range of tests, which it is believed agree more closely with field values that can be achieved with the fine sands in question. The grain size distribution and particle shape were also found to have an effect on the dry densities achieved. Researchers recommend that serious consideration be given to the adoption of vibratory test procedures for fine sands. Revisions are suggested to the material specifications for MSE wall backfill, among other things, specifying the fill in terms of gradation, plasticity, soundness, and corrosion properties. A revised material testing manual has been proposed for the testing of backfill for MSE retaining walls. A new field inspector's manual for the construction and supervision of MSE retaining wall systems has also been prepared.
- Research project title: Specifications for Backfill of Reinforced-Earth Retaining Walls.
Arlington, TX United States 76011
Austin, TX United States 78763-5051
Washington, DC United States 20590
- Morris, D V
- Delphia, J G
- Publication Date: 1999-6
- Features: Appendices; Figures; Photos; References; Tables;
- Pagination: 204 p.
- TRT Terms: Backfill soils; Construction; Dry density; Inspection; Laboratory tests; Manuals; Materials tests; Mechanically stabilized earth; Retaining walls; Sand; Soil compaction; Specifications; Test procedures
- Subject Areas: Bridges and other structures; Construction; Design; Geotechnology; Highways; I24: Design of Bridges and Retaining Walls;
- Accession Number: 00795258
- Record Type: Publication
- Report/Paper Numbers: FHWA/TX-99/1431-S,, Report 1431-S,, Project Summary
- Contract Numbers: Project No. 0-1431
- Files: TRIS, ATRI, USDOT, STATEDOT
- Created Date: Jul 10 2000 12:00AM