<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. (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 [withdrawn 2003]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>