Technical Manual: Conduits through Embankment Dams (FEMA 484)

Chapter 5—Foundation and Embankment Dam6H:1V6H:1V1H:10V1H:10VFigure 83.—Recommended earthfill ramp and conduit side slopes.compactors often try to shorten compaction time by utilizing thicker lifts andnot as much compaction. For these reasons, handheld compactors should beavoided, if possible.Close inspection is needed to ensure proper results, and extensive testing isrequired to ensure a quality earthfill. Even with the best of efforts, substandardearthfill material next to the conduit may occur, which increases the probabilityof poorly bonded lift surfaces, low density zones and poor bond between theearthfill and structure and result in the development of seepage paths(Reclamation, 1987c, pp. A-1 and A-2). In some special cases, certain areas oflarge conduits may not be accessible to heavy compaction equipment and theuse of handheld types of compactors may be unavoidable. Handheldcompactors may be required where space available for large compactionequipment is limited. Designers should consider this potential and avoid theneed for hand compaction to the extent possible.Construction specifications should also ensure that hand-compacted earthfill isnot compacted at too dry a water content. A wetter earthfill material will bemore deformable and will result in better densities and bond. The earthfill nextto the conduit should be compacted at water content between 1 percent and3 percent wet of Standard Proctor optimum.• Control testing.—The frequency of control testing should be as often as necessaryto ensure that the earthfill adjacent to the conduit is properly compacted. Atleast one dry unit weight and moisture content control test should be takenduring each shift. Use of a penetrometer to locate low dry unit weight zones, asa supplement to regular control testing, can greatly increase the effectiveness ofthe inspector.• Dry unit weight control.—Dry unit weight control of the earthfill within 1 or2 inches of the conduit surface is difficult using conventional test procedures.The inspector should make use of a penetrometer, a knife blade, or whatever123