<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. The length of the transitions range from 23 to 177 meters with heights up to 7 meters and widths of 8 to 24 meters.</p><p>Subsurface Conditions: The subsurface conditions are generally described as 5 to 35 feet of uncontrolled granular fill overlaying organic silts and clays, which are underlain by Boston Blue Clay.</p><p>Several alternatives were considered but ultimately two alternatives were chosen depending on the project geometry: The first consisted of an Expanded PolyStyrene (EPS)-geofoam fill embankment supporting the roadway structure and architectural EIFS (Exterior Insulation Finishing System) curtain walls (Alternative 1). The second design consisted of EPS-geofoam fill supporting the embankment over a drilled shaft supported slab (Alternative 2). Because of buoyancy concerns, Alternative 1 also included a fill layer of expanded clay/shale aggregate. Seismic design was a significant and controlling aspect of selection of the type of geofoam block. For construction simplicity, a uniform bock with a minimum density of 32 kg/m³ was selected that satisfied both static and dynamic design.</p><p><img class="aligncenter wp-image-3495 size-large" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Diagram showing Expanded PolyStyrene (EPS)-geofoam fill embankment supporting the roadway structure and architectural EIFS (Exterior Insulation Finishing System) curtain walls." width="1024" height="581" /></p><p><img class="aligncenter wp-image-3496 size-large" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Diagram Showing Expanded PolyStyrene, EPS-geofoam fill supporting the embankment over a drilled shaft supported slab." width="1024" height="567" /><h2>Project Technical Paper:</h2>Riad, H.L., Ricci, A.L., Osborn, P.W., D’Angelo, D.A. and Horvath, J.S. (2004). “Design of lightweight fills for road embankments on Boston’s Central Artery/Tunnel Project”. Proceedings, Fifth International Conference on Case Histories in Geotechnical Engineering, New York, NY, April 13-17.<br><h2>Date Case History Prepared:</h2>November 2012</p><p></div></p></p>