<p><p><div class="grayed-title"><strong>Analysis Procedure: DGGT Approach</strong></div>Reference(s):<br><em>DGGT AK2.8 (2002)</em><em>Kempfert and Gebreselassie (2006)</em></p><p>Combined Soil Stabilization with Vertical Columns (CSV) is a method in which 12- to 20-cm diameter columns of a dry binder or dry sand-binder mix are installed using a screw displacement auger.

<p><p><h2>Commentary</h2>The cost of Combined soil Stabilization with Vertical columns (CSV) on a highway project should be captured in a contract bid item which is measured by the lineal foot (LF). Included in this bid item are the material, equipment, labor and incidentals to construct CSV.

<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'> Component

<p><p><strong>Reference(s):</strong></p><p><em>DGGT AK2.8 (2002)</em></p><p><strong>Method Summary</strong></p><p>After installation and subsequent excavation of test columns, samples taken from test columns should be subjected to compressive strength testing in the laboratory to verify interior column capacity. It is acceptable to use load tests in place of laboratory tests to verify interior column capacity on the condition that load tests are carried out to 200% of the design load.

<p><p><strong>Reference(s):</strong></p><p><em>Coastal Caisson Corp. (2009)<br>DGGT AK2.8 (2002)<br>Dumas et al. (2003)<br>Kannan (2007)<br>Scheller and Reitmeier (2000)</em></p><p><strong>Method Summary</strong></p><p>If satisfactory results are achieved during the installation of trial columns, the same installation parameters will be used for the production columns.

<p><p><h2>Liquefaction Potential Assessment</h2>CSV 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. When CSVs are used for support of embankments and structures, to reduce settlements, or to increase slope stability, it is also necessary to confirm that there will not be a risk of liquefaction or other ground disturbance that could lead to loss of support and lateral spreading.

<p><p><strong>Reference(s):</strong></p><p><em>Coastal Caisson Corp. (2009)<br>DGGT AK2.8 (2002)<br>Dumas et al. (2003)<br>Kannan (2007)<br>Scheller and Reitmeier (2000)</em></p><p><strong>Method Summary</strong></p><p>Load tests are used to determine capacity and settlement of CSV columns. Verification tests are conducted on the test columns to validate the design assumptions and provide an estimate of capacity and settlement for all columns.

<p><p><div><img class="aligncenter wp-image-3376 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph showing equipment used to install CSV columns along Old St.

<p><p><strong>Reference(s):</strong></p><p><em>DGGT AK2.8 (2002)</em></p><p><strong>Method Summary</strong></p><p>Traditional surveying methods should be used to ensure that the as-built locations match the specified locations.

<p><p><strong>Reference(s):</strong></p><p><em>Coastal Caisson Corp. (2009)<br>DGGT AK2.8 (2002)<br>Dumas et al. (2003)<br>Scheller and Reitmeier (2000)</em></p><p><strong>Method Summary</strong></p><p>Before beginning production, it is necessary to install calibration and test columns to verify structural design and determine installation parameters for the production columns.