<p><p><div><h2>Project Summary/Scope:</h2>Construction of a 2.15-meter high embankment was required for the purpose of protecting the highway from floods. A pilot test embankment construction program was conducted using vacuum preloading. The initial test section was 390 m². Following the pilot program, the technology was adopted for up to 17,550 m² of highway.</p><p>Subsurface Conditions: 1.7-meter thick peat layer with water content ranging from 400 to 900%, underlain by 2.0-meter thick highly organic, compressible clay with water content ranging from 140 to 210%.</p><p>An 80-cm thick free-draining sand blanket was placed at the surface with an additional 0.5 meters of granular fill. Vertical drains were used on a 1.4 by 1.4-meter grid. An additional 1.3-meter surcharge was used, producing an effective load when combined with the vacuum of 150 kPa.</p><p>A PVC membrane was installed over the entire surface area of the site and was sealed in a peripheral trench with Bentonite Aquakeep slurry. Horizontal drains were installed to intercept the rising groundwater table.</p><p>Vacuum consolidation was performed for 3 months using a 25 kW pump.<br><h2>Alternate Technologies:</h2>Other solutions considered include soil replacement, raft foundation supported by piles, and surcharge preloading. Conventional surcharging was rejected due to stability concerns.<br><h2>Performance Monitoring:</h2>Settlement and pore water pressure were monitored. The total settlement after completion of vacuum consolidation was approximately 70 cm. At the end of vacuum application, the ground rebounded about 3 cm over a 48-hour period. The groundwater level increased 40 cm during vacuum application.</p><p>The primary consolidation induced by the vacuum consolidation was found equivalent to a 4.5-meter surcharge.</p><p><figure id='attachment_2634' style='max-width:747px' class='caption aligncenter'><img class="wp-image-2634 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic diagram showing the equipment and setup for applying vacuum preloading with prefabricated vertical drains." width="747" height="397" /><figcaption class='caption-text'> Vacuum Consolidation Process with PVDs (Masse et al. 2001)</figcaption></figure><h2>Project Technical Paper:</h2>Cognon, J.M., Juran, I., and Thevanayagam, S. (1994). “Vacuum consolidation technology- Principles and field experience.” <em>Vertical and Horizontal Deformations of Foundations and Embankments</em>, <em>Geotechnical Special Publication No. 40</em>, American Society of Civil Engineers, Vol. 2, 1237-1248.<br><h2>Figure Reference:</h2>Masse, F., Spaulding, C.A., Wong, I.C. and Varaksin, S. (2001) “Vacuum consolidation: a review of 12 years of successful development.” Geo-Odyssey, ASCE, Virginia Tech, Blacksburg, VA.<br><h2>Date Case History Prepared:</h2>November 2012</p><p></div></p></p>