<p><p><figure id='attachment_2542' style='max-width:397px' class='caption aligncenter'><img class="wp-image-2542 " src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic diagram showing the installation principle for combined soil stabilization with vertical columns." width="397" height="551" /><figcaption class='caption-text'> Components of the CSV system (Scheller and Reitmeier 2000).</figcaption></figure><h2>Basic Function:</h2>Combined Soil Stabilization with sand/cement Vertical Columns (CSV) is a ground improvement technique which densifies and transfers load through soft soils.<br><h2>Advantages:<em> </em></h2><ul> <li>Speedy installation</li> <li>No vibration during installation</li> <li>Soft organic soils can be treated</li> <li>No spoil is produced</li> <li>Lightweight equipment is used for installation</li> <li>Low cost relative to other technologies</li> <li>High flexibility in design and application</li></ul><h2>General Description:</h2>Preblended sand/cement columns are installed into the ground using a rotary bored displacement technique. Soil is improved by densification and load transfer.<br><h2>Geologic Applicability:</h2><ul> <li>Applicable to very soft to stiff cohesive soils, loose to medium cohesionless soils, and organic soils.</li> <li>Used to support embankments and structures.</li> <li>In loose sands, added benefit of densification of soil from installation process.</li> <li>Dewatering not required, groundwater levels are not connected to result of technology.</li> <li>Groundwater should hydrate the dry sand/cement mixture.</li></ul><h2>Construction Methods:</h2>In constructing the CSV, preblended sand/cement columns are installed into the ground using a rotary bored displacement technique. The auger in the system rotates to the opposite direction of the drilling to displace the soil while the sand cement mixture is transported from a hopper down the flights of the auger. The sand and cement is a dry mixture that is hydrated using the moisture from the ground. Depths of columns can be 30 to 40 ft (9 to 12 m) with a 6 to 8 in (15 to 20 cm) diameter and an 8 to 10 in (20 to 25 cm) diameter top. Hydration and curing time should be considered and accounted for when determining schedules.<br><h2>Additional Information:</h2>The structural capacity of an 8 in (20 cm) diameter column is about 15 kips (67 KN). Where a low load capacity is needed, the CSV may be less expensive than other technologies.<br><h2>SHRP2 Applications:</h2><ul> <li>New Embankment and Roadway Construction over Unstable Soils</li> <li>Roadway and Embankment Widening</li></ul><h2>Example Successful Applications:</h2><ul> <li>Old St. Augustine Road – Jacksonville, FL</li></ul><h2>Complementary Technologies:</h2>Most applicable to column supported embankments used with or without geosynthetic reinforced load transfer platform.<br><h2>Alternate Technologies:</h2>Sand compaction columns, stone columns, rammed aggregate piers, vibro-concrete columns, continuous flight auger piles, geotextile encased columns, deep mixing methods, and jet grouting.<br><h2>Potential Disadvantages:</h2><ul> <li>Low load capacity</li> <li>Requirement for groundwater to hydrate the dry sand/cement mixture</li> <li>Lack of simple, comprehensive, and reliable design procedure</li> <li>Lack of knowledge of technology benefits, design procedures, and construction techniques</li></ul><h2>Key References for this technology:</h2>DGGT AK2.8 (2002). “Merkblatt für die Herstellung, Bemessung und Qualitätssicherung von Stabilisierungssäulen zur Untergrundverbesserung: Teil I - CSV Verfahren (Combined Soil Stabilization with Vertical Columns).” Deutsche Gesellschaft für Geotechnik, Arbeitskreis 2.8</p><p>Kempfert, H. G. and Gebreselassie, B. (2006). “Excavations and Foundations in Soft Soils.” Springer Berlin, Heidelberg. 461-523.</p></p>