<p><p><strong>References:<br></strong><em>Fox and Cowell (1998)</em></p><p><strong>Method Summary</strong></p><p>Fox and Cowell (1998) provide a good summary of the BSTA, which is paraphrased below.</p><p><em>Bottom stabilization tests are a method of verifying that the rammed aggregate pier element being installed has achieved a general stabilization prior to the completion of installation.

<p><p><strong>References:<br></strong><em>Al-Homoud and Degen (2006)<br>Ashford et al. (2000)<br>Lopez and Shao (2007)<br>Mackiewicz and Camp (2007)<br>Schaefer et al. (2016)</em></p><p><strong>Method Summary</strong></p><p>Installation of stone columns in clean to silty sands (less than 15% fines) can densify the surrounding soil resulting in higher strengths and densities.

<p><p><strong>References:<br></strong><em>Fox and Cowell (1998)</em></p><p><strong>Method Summary</strong></p><p>Fox and Cowell (1998) provide a good summary of DCP testing for this application, which is paraphrased below.</p><p><em>DCP testing is used to verify graded base course aggregate densification within the top few feet of the pier element after tamping energy has been applied.

<p><p><strong>References:<br></strong></p><p><strong>Method Summary</strong></p><p>The shear strength and permeability of the column are dependent upon stone gradation. For QC purposes, gradation analyses should be run on stone samples prior to installation.

<p><p><h2>Project Summary/Scope:</h2>A five-story, 40,000 ft2 office building site consisting of liquefiable soils in the floodplain of the Missouri River in Missouri was remediated using Deep Dynamic Compaction (DDC) and stone columns constructed by dropping heavy weights. The required depths of treatment were greater than those provided by DDC, so stone columns were used to densify the soils at greater depths.</p><p>Subsurface conditions: The site consists of a thin layer of fill underlain by floodplain alluvium and Mississippian-age bedrock.

<p><p><strong>References:<br></strong><em>Barksdale and Bachus (1983a)<br>Schaefer et al. (2016)</em></p><p><strong>Method Summary</strong></p><p>Field load tests can be used to verify the capacity of stone columns.

<p><p><strong>References:<br></strong><em>Fox and Cowell (1998)</em></p><p><strong>Method Summary</strong></p><p>Proper installation of rammed aggregate piers requires the aggregate moisture content to be within acceptable limits. Moisture content tests can be run on aggregate samples obtained before placement.

<p><p><h2>Project Summary/Scope:</h2>Redevelopment of a sloping site adjacent to Interstate 395 in Alexandria, VA required construction of retaining walls. Rammed aggregate piers were used to support the wall, rather than large diameter drilled shafts due to economic considerations.</p><p>Subsurface conditions: Deep uncontrolled fills and large areas of marine clay.</p><p>Four rows of 750-mm diameter rammed aggregate piers were installed in a 1.5- meter triangular grid pattern. Shaft lengths extended to depths of up to 6 meters.

<p><p><strong>References:<br></strong><em>Schaefer et al. (2016)</em></p><p><strong>Method Summary</strong></p><p>Installation of stone columns in clean to silty sands (less than 15% fines) can densify the surrounding soil resulting in higher strengths and densities. PressureMeter Tests (PMTs) may be used to verify soil improvement as indicated by the horizontal earth pressure and resistance before and after stone column installation.

<p><p><h2>Project Summary/Scope:</h2>After a long period of heavy rains, the approximately 2H:1V slope began to show signs of distress. The failure led to horizontal and vertical movements of a safety barrier wall and threatened a wooded area at the toe of the slope.

<p><p><div><img class="aligncenter wp-image-3330 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of Route 22 project stone column installation.

<p><p><strong>References:<br></strong><em>Al-Homoud and Degen (2006)<br>Kumar (2001)<br>Schaefer et al. (2016)</em></p><p><strong>Method Summary</strong></p><p>Installation of stone columns in clean to silty sands (less than 15% fines) can densify the surrounding soil, resulting in higher strengths and densities. Standard Penetration Tests (SPTs) can be conducted on the soil between stone column locations before and after treatment to validate soil improvement through an increase in blow counts.

<p><p><strong>References:<br></strong><em>Carchedi et al. (2006)<br>Dwyer et al. (2006)<br>Farrel and Taylor (2004)<br>Fox and Cowell (1998)<br>Fox and Edil (2000)<br>Fox and Lien (2001a)<br>Fox et al. (2004)<br>Lillia et al. (2004)<br>Majchrzak et al (2004)<br>Schaefer et al. (2016)<br>Srinivasan et al. (2002)<br>White and Hoevelkamp (2004)<br>White et al. (2007a, c)<br>Wissman et al.

<p><p><strong>References:<br></strong><em>Al-Homoud and Degen (2006)</em></p><p><strong>Method Summary</strong></p><p>Stone consumption during construction can be monitored to ensure that the volume of stone installed is at least as large as the volume determined by the minimum diameter, length, and density. This method does not ensure uniform diameter over the length of the column. Weak strata will lead to an increase in column diameter at that depth, and therefore an increase in stone consumption.

<p><p><strong>References:<br></strong><em>Al-Homoud and Degen (2006)</em></p><p><strong>Method Summary</strong></p><p>Prior to surveying the as-built location of a stone column, the ground surface should be bladed off to a depth of 1 or 2 feet to allow the column to be better located.

<p><p><strong>References:<br></strong><em>Fox and Cowell (1998)</em></p><p><strong>Method Summary</strong></p><p>Pier spacing and as-built locations can be checked after construction to ensure agreement with the plans and specifications using traditional surveying methods.

<p><p><strong>References:<br></strong><em>Fox and Cowell (1998)</em></p><p><strong>Method Summary</strong></p><p>Uplift tests are conducted in a manner similar to modulus tests; however, during the uplift tests tensile forces are applied to the pier rather than compressive forces. The tensile force is applied through a reinforcing steel cage to the bottom of the pier. The load durations and holding criteria are the same as for the modulus test.

<p><p><strong>References:<br></strong><em>Al-Homoud and Degen (2006)</em></p><p><strong>Method Summary</strong></p><p>Stone column performance is also dependent on the verticality of the column. X-Y sensors can be mounted on the rig to ensure verticality during installation.