Summary of Rockfill Placement and Compaction ... - Ausenco

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Overbuild:Ideally the rock borrow should be sufficiently wetted so that no dust occurs when thehaul truck or scraper dumps a load on the fill surface for spreading and compacting.Wetting of the rockfill in the fill area should be accomplished prior to spreading thenew lift or following compaction of the lift. Wetting immediately prior to compactionby vibratory rollers significantly dampens the dynamic force of the compactor forinefficiency in compaction. The exception to this rule is a clean rockfill, which can beflooded with water and rapidly drained before compaction begins.An ideal rockfill moisture content contains minus 3/4 inch (19 mm) materials thatappear near optimum moisture, not overly wet or overly dry, for enhanced vibratorycompaction. Wetting before placement of each new lift is encouraged to providebonding between successive lifts without the need to scarify the compacted rockfillsurface. There is no need to scarify compacted rockfill surfaces provided the surfaceconsists of clean rock or is moist.Modern day compacted rockfills that are relatively well graded show minimal postconstructionsettlements of the order of 0.2 feet per 100 feet of height (0.2 m per 100m). For compacted large earth-rockfill dam structures with a relatively thin centralcore or upstream earthfill core/impervious liner facing, about 0.5 feet (0.15 m) crestoverbuild per 100 feet (30 m) of dam height appears conservative. For largecompacted earth-rockfill dams with relatively thick central earthfill cores, about 1 feet(0.3 m) minimum crest overbuild per 100 feet (30 m) of dam height is reasonable tocounteract the long-term consolidation of core materials (post-constructiondissipation of excess pore water pressures in fine-grained core materials).Rockfill Guidelines 4
REFERENCESBreitenbach, A. J. (1993), Rockfill Placement and Compaction Guidelines, GeotechnicalTesting Journal, ASTM, Philadelphia, Pennsylvania, Vol. 16, No. 1, pp. 76 to 84.Gloze, Alfred R. et al (1977), Design of Rockfill Dams, Chapter 7 - Handbook of DamEngineering.Pope, R. J. (1966), Evaluation of Cougar Dam Embankment Performance, ASCE SoilMechanics and Foundations Division Conference, Berkeley, California, ASCE, New York.Sherard, J. L., Woodward, R. J., Gizienski, S. F., and Clevenger, W. A. (1963), Earth andEarth-Rock Dams, Wiley, London.United States Department of the Interior, Bureau of Reclamation (1974), Rockfill Dams,Chapter 7, Design of Small Dams, Water Resources Technical Publication, Denver,Colorado.Rockfill Guidelines 5
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Summary of Rockfill Placement and Compaction ... - Ausenco

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