<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. 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>