<p><p><figure id='attachment_2632' style='max-width:1024px' class='caption alignnone'><img class="wp-image-2632 size-large" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of a pad foot traditional compaction roller." width="1024" height="768" /><figcaption class='caption-text'> Example of a pad foot traditional compaction roller. (Photograph courtesy of David White.)</figcaption></figure><h2>Basic Function</h2>As a conventional type of surface compaction, compactive energy is applied using a variety of machine rollers to densify the soils, so that soils’ engineering properties will improve thus providing more stable and reliable foundations.<br><h2>Advantages:</h2><ul> <li>Lower cost compared to alternate methods when it is properly controlled</li> <li>Reduction of subsequent consolidation and settlement of a compacted embankment</li> <li>Allows thinner pavement and lower total cost</li> <li>Shrinking and swelling effects are minimized</li></ul><h2>General Description:</h2>Compactive energy is traditionally applied using a variety of rollers depending on the type of soil to be compacted. The most prevalent types of rollers are static rollers (smooth-wheel rollers) and vibratory rollers. Other types of rollers include sheepsfoot and pad foot rollers (both static and vibratory) and rubber-tired rollers. Lift thicknesses vary from several inches (for clays and silts) to perhaps 2 ft for free-draining fills (sands and gravels).<br><h2>Geologic Applicability:</h2><ul> <li>A wide range of soils can be treated using this method, depending upon roller type.</li> <li>Sheepsfoot rollers are used predominately for finegrained soils.</li> <li>Rubber tire rollers are used for coarse-grained and finegrained soils.</li> <li>Smooth wheel rollers are used for subgrade or base course compaction of well-graded sand-gravel mixtures.</li> <li>Vibrating rollers are used primarily for coarse-grained soils such as sand-gravel mixtures.</li></ul><h2>Construction Methods:</h2>The usual design-construct procedure is as follows: laboratory tests are conducted on samples of the proposed soil materials to be used to define the engineering properties required for design. Appropriate compaction specifications are selected, field compaction control tests are specified, and the result of these tests become the standard for controlling the project. Construction control tests are then conducted to ensure that the contractor actually adheres to<br>the compaction specifications.<br><h2>Additional Information:</h2>The compaction design procedure typically uses the Proctor laboratory test (ASTM D698; AASHTO T99 or ASTM 1557; AASHTO T180) to determine the maximum dry density and optimum water content of the soil. QA/QC procedures are usually sufficient although they do not provide adequate coverage of the improved area and rely upon proof rolling for verification. Both cost information and specifications are easy to obtain.</p><p>SHRP2 Applications:<br><ul> <li>Embankment and roadway construction over unstable soils</li> <li>Roadway and embankment widening</li> <li>Stabilization of pavement working platforms</li></ul><h2>Example Successful Applications:</h2>This technology is well-established and widely used by state agencies and contractors are readily available.<br><h2>Complementary Technologies:</h2>Excavation and replacement<br><h2>Alternate Technologies:</h2>Rapid Impact Compaction, Intelligent Compaction, High Energy Impact Rollers<br><h2>Potential Disadvantages:</h2><ul> <li>Compaction will reduce the permeability (drainage properties) of subgrade and base.</li> <li>Densification occurs in limited thicknesses and required multiple passes to achieve design densities.</li></ul><h2>Key References for this Fact Sheet:</h2>Christopher, B.R., Schwartz, C., and Boudreau, R. (2010). “Geotechnical Aspects of Pavements”, Report No. NHI-05-037.</p><p>Das, B.M. (2006). Principles of Geotechnical Engineering, 6th Ed., Thomson, Toronto.</p><p>Holtz, R.D. (1990). “Compaction Concepts”, State of the Art Report 8: Guide to Earthwork Construction, Transportation Research Board, Washington D.C.</p><p>United States. (1992). “Military Soils Engineering,” Field Manual 5-410, Washington, DC: Headquarters, Dept. of the Army</p></p>