<p><p><h2>Commentary</h2>Quantifying the cost of compaction using high energy impact rollers is difficult. In simplest terms, the capital investment plus depreciation and maintenance costs must be pro‑rated over a given amount of embankment compaction. Availability of high energy impact rollers in the U.S. is limited at this time. As a one-time trial, investment in an additional fixed cost is typically not feasible.

<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.

<p><p><strong>Liquefaction Potential Assessment</strong></p><p>There are no documented case histories where IR technology was used for liquefaction mitigation. Some general guidance related to liquefaction potential assessment is provided below.</p><p>IR technology may be used at sites with in-situ soils that may be susceptible to liquefaction during earthquakes. Saturated sands, silty sands, sandy silts, and silts are likely to be in this category.

<p><p><strong>References:<br></strong><em>Avalle and Grounds (2004)<br>Avsar et al.

<p><p><strong>References:<br></strong><em>Auzins and Southcott (1999)<br>Avalle and Carter (2005)<br>Avalle and Grounds (2004)<br>Avsar et al.

<p><p><strong>References:<br></strong><em>Auzins and Southcott (1999)<br>Avalle (2004a,b)</em></p><p><strong>Method Summary</strong></p><p>Permeability and infiltration tests are conducted to determine the coefficient of permeability and infiltration rate of the materials, respectively. Use of in-situ Guelph permeameter is reported by Auzins and Southcott (1999) to monitor change in permeability with increasing IR passes.

<p><p><strong>References:</strong></p><p><strong></strong><strong>Method Summary</strong></p><p>Compacted soil sampling from borings to get “undisturbed” samples is an effective method for laboratory strength and modulus testing. Soil sampling from on-site stock piles can be helpful to conduct classification, compaction, strength, and modulus testing.

<p><p><strong>References:<br></strong><em>Avalle and Grounds (2004)<br>Landpac (2008b)</em></p><p><strong>Method Summary</strong></p><p>Static Plate Load Tests (PLTs) involve obtaining load versus deflection curves to determine modulus of subgrade reaction, soil elastic modulus, or soil bearing capacity. The test is conducted by increasing a static load on the soil and recording the corresponding plate deflections. Avalle and Grounds (2004) documented the procedure using a 320-mm diameter plate for testing.

<p><p><div></p><p><figure id='attachment_3462' style='max-width:300px' class='caption aligncenter'><img class="wp-image-3462 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph showing a trial section after 5 passes, Trans Kalahari Highway, Botswana, Africa." width="300" height="262" /><figcaption class='caption-

<p><p><strong>References:<br></strong><em>Avalle (2007b)<br>Avalle and Carter (2005)<br>Bouazza and Avalle (2006 a,b)</em></p><p><strong>Method Summary</strong></p><p>Ground vibrations due to IR passes are monitored to assess its influence on nearby building structures.

<p><p><strong>References:<br></strong><em>Avalle (2004b)<br>Pinrad (1999, 2001)<br>Scott and Suto (2007)</em></p><p><strong>Method Summary</strong></p><p>IR can be used as a “proof compactor” or “proof roller” to visually identify soft spots that need additional compaction or rework. Avalle (2004b), Pinrad (1999, 2001), and Scot and Suto (2007) documented field observations effectively using the IR as a “proof roller”.