<p><p><div><h2>Project Summary/Scope:</h2>As part of the “Big Dig” in Boston, MA, multiple viaducts, bridges, transition structures, and boat and tunnel sections were required. Eight of these transition structures and ramps utilized lightweight fill alternatives.

<p><p><strong>References:<br></strong><em>Schaefer et al. (2016)</em></p><p><strong>Method Summary:</strong></p><p>Construction observation is an important QC/QA method for all lightweight fill projects to ensure proper placement and compaction of fill material. For wood fibers, shredded tires, or other fill materials where density testing is not possible, observations are vital to ensure proper compaction.

<p><p><strong>References:</strong></p><p><strong>Method Summary</strong></p><p>Standard density testing using a nuclear density gauge, sand cone, balloon density gauge, or other method should be used to verify compaction of lightweight fill materials that are composed of granular particles and have lower void ratios, such as fly ash and slag aggregate. Field density should be compared with laboratory proctor tests to determine relative compaction of fill material.

<p><p><strong>Current FHWA Reference(s):<br></strong><em>Schaefer et al. (2016)</em><strong>Supporting Reference(s):<br></strong><em>Christopher et al. (2006)<br>NYSDOT (2008)</em></p><p>Lightweight fills have been used in the geotechnical design of highway embankments to reduce the possibility of ultimate and serviceability failures. Ultimate failures are generally described as the total collapse of the embankment.

<p><p><figure id='attachment_3497' style='max-width:884px' class='caption aligncenter'><img class="wp-image-3497 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph showing the geofoam placement at the Geofoam Research Center, Syracuse University." width="884" height="540" /><figcaption class='caption-text'> (Photograph cou