<p><p><figure id='attachment_1478' style='max-width:662px' class='caption aligncenter'><img class="wp-image-1478 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of a Landpac 25-kJ three sided impact roller." width="662" height="437" /><figcaption class='caption-text'> Landpac 25-kJ three-sided impact roller. Photograph from www.landpac.co.za, courtesy of Land Pac®</figcaption></figure><h2>Basic Function</h2>High energy Impact Roller (IR) technology transfers high-impact compaction energy to densify/rubblize in-situ materials.<br><h2>Advantages:</h2><ul> <li>Subgrade can be improved from the surface without overexcavation and replacement</li> <li>Can crush rock/concrete into rubble</li> <li>Can compact thick soil lifts and thus increase compaction productivity</li> <li>Achieves high density</li></ul><h2>General Description:</h2>High energy impact roller technology uses a lifting and falling motion to compact the soil. The roller is pulled at high speeds, 6 to 7.5 mph (10 to 12 km/h), to generate a high impact force that densifies materials. IRs can densify existing fill, collapsible sands, landfill waste, mine haul roads, and bulk earthwork. It can also be used to rubblize existing pavement to create a new subbase.<br><h2>Geologic Applicability:</h2><ul> <li>Suitable for a wide variety of materials: clays, silts, sands, rocks/boulders, dredged fill, and industrial waste.</li> <li>Compaction improvement depth depends on the type of material and stratigraphy, but can be as much as 16.4 feet (5 meters) and generally up to 6.6 feet (2 meters).</li></ul><h2>Construction Methods:</h2>High energy impact roller technology uses non-circular shaped tow-behind solid steel molds.<br><h2>Additional Information:</h2>Impact rollers can densify materials to depths greater than conventional static or vibratory rollers. A recent development in the IR technology is Landpac’s Continuous Impact Response (CIR) system. The CIR system involves instrumenting the IR drum with an accelerometer and continuously monitoring the decelerations (in g’s) integrated with a Global Positioning System (GPS) and presenting the results as a map in real-time to the operator.<br><h2>SHRP2 Applications:</h2><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><ul> <li>Doha International Airport, Qatar</li> <li>Reconstruction of the Trans Kalahari Highway, The Republic of Botswana, Africa</li> <li>The Port River Expressway, Adelaide, Australia</li> <li>Port Coogee Marina Project, Western Australia</li></ul><h2>Complementary Technologies:</h2><ul> <li>Intelligent compaction and traditional compaction</li> <li>Alternate Technologies:</li> <li>Deep foundations, deep dynamic compaction, stone columns, compaction grouting, excavation and replacement, rapid impact compaction</li></ul><h2>Potential Disadvantages:</h2><ul> <li>The upper 4 to 6 inches (100 to 150 mm) of the surface is disturbed/shattered.</li> <li>Small sites with complex geometries limit the driving speeds, and it may not be possible to densify all areas.</li> <li>Vibrations may affect nearby structures.</li></ul><h2>Key References for this Fact Sheet:</h2>Clegg, B., and Berrangé, A.R. (1971). “The development and testing of an impact roller,” Trans. S. Afr. Instn. Civ. Engs. Vol. 13, No. 3, pp. 65-73.</p><p>Avalle, D.L. (2007). “Trials and validation of deep compaction using the “square” impact roller.” Australian Geomechanics Society Sydney Chapter Mini-Symposium: Advances in Earthworks, 17 October, Sydney, Australia.</p><p>Pinrad, M.I. (2001). “Development in compaction technology”, Geotechnics for Roads, Rail Tracks, and Earth Structures, Edited by Correia, A.G., and Brandl H., A.A. Balkema Publishers, The Netherlands.</p></p>