<div class='content-section' id='qc-qa-guidelines-generally-applicable-to-stone-columns' title='QC/QA Guidelines Generally Applicable to Stone Columns'><p><p><h2>QC/QA Guidelines Generally Applicable to Stone Columns</h2>A comprehensive stone column QC/QA assessment program usually consists of several QC/QA methods. Gradation, specific gravity, loose density, and compacted density tests should be run on the stone to be installed, with a frequency of one test for each 5,000 tons of material prior to construction to ensure compliance with specifications (Elias et al. 2006a). Stone column performance is dependent upon the integrity of the column. It is important that the minimum column diameter and required compacted density of the stone be achieved in order to ensure the desired performance. During construction, stone consumption, in terms of buckets of a known weight or volume, should be monitored as a function of depth. Based on the loose and in-place density of the stone, it is possible to estimate the column diameter. Barksdale and Bachus (1983a) provide a method for estimating the in-place density of the stone based on loose and compacted densities if actual data is not available. Measurements should typically be taken at a maximum of 5-foot increments to determine the column’s cross-sectional area profile vs. depth. Decreased rate of stone consumption may indicate caving of the hole or failure to attain adequate displacement and replacement of the surrounding ground. For any group of 50 consecutively installed stone columns, the average diameter over the total length should not be less than as specified in the contract documents. No stone column should have a diameter less than 90% of the minimum diameter specified in the contract documents. Verticality of the rig should be monitored, and no stone column axis should be inclined from the vertical by more than 2 inches in 10 feet. During construction of the column, each lift should be re-penetrated until the specified amp-meter reading is achieved, thus indicating good input energy from the vibrator probe to the stone. In general, it is recommended that, as a minimum, the vibrator free-standing current reading plus at least 40 additional amps be developed (Elias et al. 2006a).</p><p>For projects requiring the improvement of large areas, it is desirable to subdivide the total area into approval or acceptance zones on the order of 100 feet on a side. Completing the work with timely approval on a zone-by-zone basis means that the contractor may proceed without risk of having to return late in the project to correct deficiencies that developed early in the project.</p><p>All construction records should be furnished to the engineer, with the following data to be obtained during column installation (Elias et al. 2006a):<br><ul> <li>Stone column reference number</li> <li>Measurement of rig verticality</li> <li>Elevation of top and bottom of each stone column</li> <li>Number of buckets of stone backfill in each stone column</li> <li>Amperage achieved as a function of depth. The date and column identification should be written on each record</li> <li>Time to penetrate and time to form each stone column</li> <li>Details of obstructions, delays, and any unusual ground conditions</li> <li>Digital data log of amperage, depth, and stone consumption</li></ul>Post-construction QC/QA is dependent on the specific application and the type of ground in which the stone columns are installed. For slope stabilization, structure or embankment support, settlement reduction, liquefaction mitigation, and prevention of lateral spreading applications in silty and clayey sands where densification is required, in-situ testing (SPT, CPT, or PMT) should be conducted at central points between the columns. Penetration resistance should be verified against values that were used to determine column spacing. The same test method should be utilized both before and after the stone column installation to verify soil improvement.</p><p>Stone column installation is not expected to induce densification of soft, saturated clays. If the columns are to support a structure or embankment in such soils, load tests are sometimes required to determine the short-term capacity and settlement of the column. Short-term load tests should be conducted in accordance with ASTM D1143, Standard Test Methods for Deep Foundations Under Static Axial Compressive Load, on individual columns after all pore pressures induced by construction have dissipated. If settlement is a primary concern, longer-term load tests are highly recommended, with settlement readings generally taken over a one-week period. The longer-term load tests should be conducted on a minimum of three to four stone columns located within a group of nine to 12 columns having the proposed spacing and pattern (Elias et al. 2006a). The load should be applied over the tributary area of the columns and may consist of column backfill material, native material, and/or the dead weight from the short-term load tests. Concrete blocks and reaction pile systems may also be used for load testing of single columns. Loading procedures for short- and long-term tests are available in Elias et al. (2006a). Surveying methods should be used to ensure proper column spacing and location. No column should be more than 4 inches from the specified center location unless an obstruction is encountered. In case of an obstruction, the Engineer should be notified to determine the maximum allowable offset. Gradation analyses on samples taken from installed columns may be used to confirm that the in-situ gradation matches the specifications and that the columns have not been penetrated by excessive amounts of fines from the surrounding ground. Such testing may be appropriate for the owner's information in a method specification, but columns cannot be rejected for failing to meet a post-installation gradation criterion if other provisions of a method specification have been followed.</p></p></div>

<div class='content-section' id='qc-qa-guidelines-applicable-to-rammed-aggregate-piers' title='QC/QA Guidelines Applicable to Rammed Aggregate Piers'><p><p><h2>QC/QA Guidelines Applicable to Rammed Aggregate Piers</h2>A comprehensive rammed aggregate pier QC/QA assessment program usually consists of several QC/QA methods. It is the responsibility of the QC representative to coordinate with the General Contractor on footing layout and pier elevations, observe installation procedures, ensure the aggregate moisture content is within acceptable limits, perform tests on production piers, and implement corrective measures when necessary. The Bottom STAbilization test (BSTA) is used to verify piers have an adequate stabilized bottom (Fox and Cowell 1998). It involves re-tamping the bottom of the piers to verify that displacement is within acceptable limits. A pattern of successful BSTA tests is sufficient to reduce BSTA verification to spot checks (Fox and Cowell 1998). The Dynamic Cone Penetrometer (DCP) is used in general accordance with ASTM STP 399 <em>Vane Shear and Cone Penetration Resistance Testing of In-Situ Soils</em> to verify aggregate densification within the top few feet of the pier. If average penetration resistance measured consistently exceeds 15 blows, and less than 10% of tests fall below 15 blows per 1.75 inches, then testing may be reduced to spot checks (Fox and Cowell 1998). Modulus testing is used to verify stiffness modulus design assumptions and is based largely on ASTM D1143 <em>Standard Test Methods for Deep Foundations Under Static Axial Compressive Load</em> and ASTM D1194 <em>Standard Test Method for Bearing Capacity of Soil for Static Load and Spread Footings </em>[withdrawn 2003]. One key difference is that the modulus test typically limits the maximum test load to 150% of the maximum designed stress. Typically, one stiffness modulus test is conducted per project site for small projects. On larger projects, between two and four stiffness modulus tests may be conducted. As a general rule, one stiffness modulus test is performed per 1,000 piers (Collin 2007a). Uplift tests are conducted when necessary to verify the performance of piers in tension. They are largely based on ASTM D3689 <em>Standard Test Methods for Deep Foundations Under Static Axial Tensile Load</em> and generally follow the same load and holding criteria as the modulus test. Often, it is possible to conduct an uplift load test at the same time as the modulus load test, since uplift pier elements are generally used as anchor reactions for the modulus test load frame (Fox and Cowell 1998). All loading and test procedures are available in Collin (2007a) and Fox and Cowell (1998). Surveying methods should be used to verify pier locations. The center of each pier should be within four inches of the plan location.</p><p>Included in the QC procedures should be the completion of daily reports during installation, which include the following information:<br><ul> <li>Footing and pier location</li> <li>Pier length and drilled diameter</li> <li>Planned and actual pier elevations at the top and bottom of the element</li> <li>The number of lifts and time of tamping for each lift placed</li> <li>Average lift thickness for each pier</li> <li>Documentation of soil conditions during drilling for comparison with soil conditions in boring logs</li> <li>Depth to groundwater, if encountered</li> <li>Documentation of any unusual conditions encountered (e.g., sloughing)</li> <li>Type and size of densification equipment used</li></ul>QA procedures include monitoring installation of modulus and uplift load test piers, monitoring load tests, performing DCP testing, and monitoring daily pier installation, including observing subsurface conditions and soils during installation.</p></p></div>

<div class='content-section' id='individual-qc-qa-methods-generally-applicable-to-stone-columns' title='Individual QC/QA Methods Generally Applicable to Stone Columns'><h2 class=''>Individual QC/QA Methods Generally Applicable to Stone Columns</h2><p><p><h2> Individual QC/QA Methods</h2>The following are generally applicable to stone columns.</p></p><div class='content-subsection' id='spt-soils-between-columns-' title='SPT (Soils Between Columns)' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>SPT (Soils Between Columns)</div><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. It is important that locations be identical before and after treatment to provide an accurate depiction of the level of improvement. Though stone columns may increase the strength of some cohesive soils, several months or more may be required before the beneficial effect is observed (Barksdale and Bachus 1983a). Therefore, stone columns are not considered an effective means of increasing the strength of cohesive soils and function primarily as reinforcing elements. SPTs are not typically performed when stone columns are installed in cohesive soils.</p><p><strong>Accuracy and Precision</strong></p><p>Accuracy and precision are limited by the procedure and mechanics of standard penetration testing.</p><p><strong>Adequacy of Coverage</strong></p><p>The SPT is a relatively costly QC/QA technique and does not provide continuous profiling. So, the number of locations evaluated is limited.</p><p><strong>Implementation Requirements </strong></p><p>The SPT is widely used and the equipment is typically readily available.</p><p><strong>General Comments</strong></p><p>The SPT provides correlations to soil strength and density, making it useful for evaluating soil improvement for slope stabilization, support of structures, support of embankments, settlement reduction, liquefaction mitigation, and prevention of lateral spreading. This method is not suitable for assessing properties of saturated cohesive soils between columns.</p></p></div><div class='content-subsection' id='cpt-soils-between-columns-' title='CPT (Soils Between Columns)' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>CPT (Soils Between Columns)</div><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. Cone Penetration Tests (CPTs) may be used to verify soil improvement as indicated by the CPT penetration resistance of the soil before and after stone column installation. It is important that locations be identical before and after treatment to provide an accurate depiction of the level of improvement. Though stone columns may increase the strength of some cohesive soils, several months or more may be required before the beneficial effect is observed (Barksdale and Bachus 1983a). Therefore, stone columns are not considered an effective means for increasing the strength of cohesive soils and function primarily as reinforcing elements. CPTs are not typically performed when stone columns are installed in cohesive soils.</p><p><strong>Accuracy and Precision</strong></p><p>When coupled with local experience and judgment, the CPT can provide accurate and precise information.</p><p><strong>Adequacy of Coverage</strong></p><p>The CPT allows continuous testing of a soil profile.</p><p><strong>Implementation Requirements </strong></p><p>The CPT is widely used and the equipment is typically readily available.</p><p><strong>General Comments</strong></p><p>The CPT provides correlations to soil strength, making it useful for ensuring quality for slope stabilization, support of structures, support of embankments, settlement reduction, liquefaction mitigation, and prevention of lateral spreading.</p></p></div><div class='content-subsection' id='pmt-soils-between-columns-' title='PMT (Soils Between Columns)' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>PMT (Soils Between Columns)</div><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. It is important that locations be identical before and after treatment to provide an accurate depiction of the level of improvement. Though stone columns may increase the strength of some cohesive soils, several months or more may be required before the beneficial effect is observed (Barksdale and Bachus, 1983a). Therefore, stone columns are not considered an effective means for increasing the strength of cohesive soils and function primarily as reinforcing elements. PMTs are not typically performed when stone columns are installed in cohesive soils.</p><p><strong>Accuracy and Precision</strong></p><p>When combined with local experience and judgment, the PMT can provide accurate and precise information about soil stiffness. Quality of test results is dependent on disturbance of the PMT borehole sidewalls.</p><p><strong>Adequacy of Coverage</strong></p><p>The PMT only allows interval, rather than continuous, testing.</p><p><strong>Implementation Requirements </strong></p><p>The PMT is not as readily available as other in-situ testing methods such as the SPT or the CPT. It is also more time-consuming and costly.</p><p><strong>General Comments</strong></p><p>The PMT provides a measure of soil stiffness, making it useful for verifying quality for slope stabilization, support of structures, support of embankments, settlement reduction, liquefaction mitigation, and prevention of lateral spreading.</p></p></div><div class='content-subsection' id='load-tests' title='Load Tests' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Load Tests</div><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. Three types of load tests can be used:<br><ul> <li>Short-term tests, which are the most common type, are used to evaluate stone column bearing capacity.</li> <li>Long-term tests, which are used to measure the consolidation settlement characteristics.</li> <li>Horizontal or composite shear tests, which are used to evaluate the composite stone-soil shear strength for use in stability analyses.</li></ul>Short-term load tests, which are similar to pile load tests, should be performed after all excess pore pressures induced during construction have been dissipated (Barksdale and Bachus 1983a). The load may be applied over a single column cross section or over an area consisting of the column plus the surrounding tributary area within the pattern of columns, depending on whether individual column or composite column plus soil properties and behavior are to be determined.</p><p>During construction, a few short-term load tests can be performed for quality control purposes. The maximum applied load for such tests is usually 150 to 200% of the allowable/design load (Barksdale and Bachus 1983a).</p><p><strong>Accuracy and Precision</strong></p><p>Load tests provide direct measurements; however, the load applied to a single column may not reach the bottom of the column, as would be the case for a large loaded area containing many columns, and may not be a true indicator of the column capacity.</p><p><strong>Adequacy of Coverage</strong></p><p>Load tests measure the performance of the column; however, it would be time and cost prohibitive to test every column using load tests.</p><p><strong> </strong><strong>Implementation Requirements </strong></p><p>Load tests require the mobilization of specialized equipment and instrumentation.</p><p><strong>General Comments</strong></p><p>Load tests can be used to measure the axial capacity of a single stone column or the composite stone column load-settlement and shear strength, making this method suitable for slope stabilization and structural support applications.</p></p></div><div class='content-subsection' id='stone-consumption-monitoring' title='Stone Consumption Monitoring' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Stone Consumption Monitoring</div><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. Conversely, a decrease in stone consumption indicates caving of the hole and/or insufficient displacement/replacement of the native ground.</p><p><strong>Accuracy and Precision</strong></p><p>Stone consumption monitoring provides a good indication of the volume of stone installed.</p><p><strong> </strong><strong>Adequacy of Coverage</strong></p><p>Stone consumption measurements are typically taken in 5-foot increments, which results in a profile of stone vs. depth.</p><p><strong>Implementation Requirements </strong></p><p>Stone consumption monitoring can easily be implemented by observing and measuring the amount of stone inserted into the hole.</p><p><strong>General Comments</strong></p><p>Stone consumption monitoring helps ensure proper column geometry and density, which is important for all stone column applications.</p></p></div><div class='content-subsection' id='surveying-methods' title='Surveying Methods' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Surveying Methods</div><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. The center of the column can then be located using traditional surveying methods to ensure that the as-built locations match the specified locations.</p><p><strong>Accuracy and Precision</strong></p><p>Most surveying methods provide greater accuracy and precision than required for this application.</p><p><strong> </strong><strong>Adequacy of Coverage</strong></p><p>Surveying methods can be used to quickly ensure proper spacing and location of all stone columns on a site.</p><p><strong>Implementation Requirements </strong></p><p>This method is readily available and can be quickly implemented.</p><p><strong>General Comments</strong></p><p>Surveying methods help ensure proper column pattern geometry, which is important for all stone column applications.</p></p></div><div class='content-subsection' id='visual-inspection-of-rig-verticality' title='Visual Inspection of Rig Verticality' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Visual Inspection of Rig Verticality</div><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. Visual inspection of rig verticality and/or a level can also be used.</p><p><strong>Accuracy and Precision</strong></p><p>Visual inspection of verticality can be subjective and difficult to perform, however levels and/or X-Y sensors can be used to improve the accuracy of determinations.</p><p><strong>Adequacy of Coverage</strong></p><p>Continuous monitoring of rig verticality can provide an indication of the verticality profile of the entire column.</p><p><strong>Implementation Requirements </strong></p><p>No special equipment is required for this method.</p><p><strong>General Comments</strong></p><p>Column verticality is important for all stone column applications.</p></p></div><div class='content-subsection' id='gradation-analyses-' title='Gradation Analyses ' ><h4 class=''>Gradation Analyses </h4><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Gradation Analyses</div><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. Gradation analyses should also be run on samples taken from the column after installation to ensure that the in-place gradation meets the specifications.</p><p><strong>Accuracy and Precision</strong></p><p>Gradation analyses provide the grain-size distribution of the sample tested, but not necessarily of the column as a whole.</p><p><strong>Adequacy of Coverage</strong></p><p>See comment for <em>Accuracy and Precision</em>.</p><p><strong>Implementation Requirements </strong></p><p>Gradation analyses are quickly and inexpensively run by all soils testing laboratories.</p><p><strong>General Comments</strong></p><p>Proper stone gradation is important for all stone column applications.</p><p>&nbsp;</p></p></div></div>

<div class='content-section' id='individual-qc-qa-methods-generally-applicable-to-rammed-aggregate-piers' title='Individual QC/QA Methods Generally Applicable to Rammed Aggregate Piers'><h2 class=''>Individual QC/QA Methods Generally Applicable to Rammed Aggregate Piers</h2><p><p><h2>Individual QC/QA Methods</h2>The following are generally applicable to rammed aggregate piers.</p></p><div class='content-subsection' id='surveying-methods' title='Surveying Methods' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Surveying Methods</div><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. Drill depths and top of pier elevations should also be checked to ensure that the constructed pier length matches the specified length.</p><p><strong>Accuracy and Precision</strong></p><p>Most surveying methods provide greater accuracy and precision than required for this application.</p><p><strong>Adequacy of Coverage</strong></p><p>Surveying methods can be used to quickly confirm proper spacing location, and length of all piers on site.</p><p><strong>Implementation Requirements </strong></p><p>This method is readily available and easily implemented.</p><p><strong>General Comments</strong></p><p>Surveying methods help ensure proper pier geometry, which is important for all applications.</p></p></div><div class='content-subsection' id='moisture-content-tests' title='Moisture Content Tests' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Moisture Content Tests</div><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. Moisture content testing is inappropriate for clean stone.</p><p><strong>Accuracy and Precision</strong></p><p>Reasonably accurate moisture contents can be obtained using oven-dried, fry pan, or Speedy Moisture Meter methods.</p><p><strong>Adequacy of Coverage</strong></p><p>Care should be taken to ensure samples used for testing are representative.</p><p><strong>Implementation Requirements </strong></p><p>This method can easily be implemented in the field (fry pan and Speedy Moisture Meter methods) or the lab (oven-dried method).</p><p><strong>General Comments</strong></p><p>Aggregate moisture content is relatively important for all rammed aggregate pier applications.</p></p></div><div class='content-subsection' id='bottom-stabilization-test-bsta-' title='Bottom STAbilization Test (BSTA)' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Bottom STAbilization Test (BSTA)</div><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. It is also a method to determine that the pier elements are comparable in quality to the load test pier elements. This test may be performed on top of the bottom bulb, or after one or several lifts have been constructed on top of the bottom bulb. When the compacted aggregate and foundation soil becomes stiff enough such that the displacement during the BSTA is less than 1.5 times the value observed during the modulus test pier construction, bottom stability has been achieved. A pattern of successful BSTA observations is sufficient to reduce BSTA verification to spot checks. </em></p><p><strong>Accuracy and Precision</strong></p><p>This method provides an empirically-derived qualitative evaluation of bottom stability.</p><p><strong>Adequacy of Coverage</strong></p><p>The stability of the bottom of the pier provides an indication of the performance of the entire pier.</p><p><strong>Implementation Requirements </strong></p><p>This method requires only the equipment needed for pier installation.</p><p><strong>General Comments</strong></p><p>Bottom stability is important for almost all rammed aggregate pier applications.</p></p></div><div class='content-subsection' id='dynamic-cone-penetrometer-dcp-testing-' title='Dynamic Cone Penetrometer (DCP) Testing ' ><h4 class=''>Dynamic Cone Penetrometer (DCP) Testing </h4><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Dynamic Cone Penetrometer (DCP) Testing</div><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. DCP testing does not need to be conducted on every pier element, unless unacceptable DCP test results, questionable aggregate moisture content, or questionable aggregate gradation requires additional verification of aggregate densification. DCP testing is inappropriate for clean stone and is only used for graded base course stone. </em></p><p><strong>Accuracy and Precision</strong></p><p>DCP blow counts are empirically correlated to density, and have proven to give reasonably accurate results.</p><p><strong>Adequacy of Coverage</strong></p><p>DCP testing only provides an indication of density in the vicinity directly beneath the cone.</p><p><strong>Implementation Requirements </strong></p><p>This method can be quickly and easily implemented.</p><p><strong>General Comments</strong></p><p>Aggregate density, and therefore DCP testing, is important for all rammed aggregate pier applications.</p></p></div><div class='content-subsection' id='stiffness-modulus-test' title='Stiffness Modulus Test' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Stiffness Modulus Test</div><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. (2001a, b)</em></p><p><strong>Method Summary</strong></p><p>Fox and Cowell (1998) provide a good summary of the modulus test for this application, which is paraphrased below.</p><p><em>Stiffness modulus is determined by performing a load tests in general accordance with ASTM D 1143 and ASTM D 1194</em> [withdrawn 2003]<em>. A vertical pressure is applied to the top of a pier element in a series of load increments, which are based on the maximum stress on the pier element calculated for the project. The maximum applied test load is typically 150% of the maximum design load. The loads are applied to the pier using a hydraulic jack and load frame. At each load increment the deflection is measured using dial gauges. The load is maintained until the rate of deflection is less than 0.01 inches per hour or until the maximum time duration is reached, whichever occurs first. A typical load schedule including load durations is provided as Table 2 below. The deflection for each load increment is then plotted against the stress for that increment. The modulus used for design is equal to the design stress divided by the corresponding deflection at that stress. The stiffness modulus is then used for estimating the settlement of the reinforced zone. </em><h3>Table 2. Typical Geopier load schedule (Fox and Cowell 1998).</h3><table class='tablepress' id='tablepress-1913'><thead><th><center>Increment</th><th><center>Approx. Stress on Geopier Element (%of max,. design)</th><th><center>Minimum Duration, Minutes
</th><th><center>Maximum Duration, Minutes</th></thead><tbody><tr><td ><center>Seat</td><td > <center>< 9</td><td > <center>N/A</td><td > <center>N/A </td></tr><tr><td > <center>1</td><td > <center>17</td><td > <center>15</td><td > <center>60</td></tr><tr><td > <center>2</td><td > <center>33</td><td > <center>15</td><td > <center>60</td></tr><tr><td > <center>3</td><td > <center>50</td><td > <center>15</td><td > <center>60</td></tr><tr><td > <center>4</td><td > <center>67</td><td > <center>15</td><td > <center>60</td></tr><tr><td > <center>5</td><td > <center>83</td><td > <center>15</td><td > <center>60</td></tr><tr><td > <center>6</td><td > <center>100</td><td > <center>15</td><td > <center>60</td></tr><tr><td > <center>7</td><td > <center>117*</td><td > <center>60</td><td > <center>240</td></tr><tr><td > <center>8</td><td > <center>133</td><td > <center>15</td><td > <center>60</td></tr><tr><td > <center>9</td><td > <center>150</td><td > <center>N/A</td><td > <center>N/A</td></tr><tr><td > <center>10</td><td > <center>100</td><td > <center>N/A</td><td > <center>N/A</td></tr><tr><td > <center>11</td><td > <center>66</td><td > <center>N/A</td><td > <center>N/A</td></tr><tr><td > <center>12</td><td > <center>33</td><td > <center>N/A</td><td > <center>N/A</td></tr><tr><td > <center>13</td><td > <center>0</td><td > <center>N/A</td><td > <center>N/A</td></tr></tbody></table><br><p class="disclaimer">*=longer load increment</p><strong>Accuracy and Precision</strong></p><p>This test provides a direct measurement of the stiffness modulus of the aggregate; however the modulus is conservatively defined as the top of pier stress divided by the deflection at the top of the pier. This procedure gives conservative (i.e., reliable), but not always accurate, values of the stiffness modulus.</p><p><strong>Adequacy of Coverage</strong></p><p>The method provides a measure of the modulus of the entire pier, rather than testing discrete points or samples within the pier. Any major discontinuities will affect the capacity, and will become evident during the test. Only a limited number of tests can be performed on a project.</p><p><strong>Implementation Requirements </strong></p><p>Stiffness modulus tests require the mobilization of specialized equipment and instrumentation.</p><p><strong>General Comments</strong></p><p>Load tests provide a measure of the stiffness modulus of the pier, which affects settlement performance.</p><p><strong> </strong></p></p></div><div class='content-subsection' id='uplift-test' title='Uplift Test' ><p><p><div class="grayed-title"><strong>QC/QA Method: </strong>Uplift Test</div><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. The deflection due to the design load is then compared to performance criteria.</p><p><strong>Accuracy and Precision</strong></p><p>This method provides a direct measurement of pier uplift capacity.</p><p><strong>Adequacy of Coverage</strong></p><p>Uplift tests measure the uplift capacity of the entire pier. Any major discontinuities will affect the capacity, and will become evident during the test. Typically, only a few tests are performed on a project.</p><p><strong>Implementation Requirements </strong></p><p>Uplift tests require the mobilization of specialized equipment and instrumentation.</p><p><strong>General Comments</strong></p><p>Load tests provide a measure of the uplift capacity of a rammed aggregate pier, making this method applicable only to the support of structures.</p></p></div></div>