<p><p><strong>Reference(s):</strong></p><p><em>Brown et al. (2007)</em></p><p><strong>Method Summary</strong></p><p>Brown et al. (2007) present a performance-based specification in which the contractor is responsible for computing static resistance, setting pile length requirements for a given design axial loading, and verifying that the performance requirements are satisfied via the use of load tests. Load tests are performed in the pre-production phase to verify that proposed construction procedures are capable of producing the desired performance and on a specified percentage of production piles to verify performance of piles installed during the construction phase.</p><p>The side shear component is mobilized with relatively small pile vertical displacements relative to the surrounding soil, typically less than 10 mm (0.4 inches). The end bearing component is fully mobilized with larger displacements, typically at a pile tip movement in the range of 5% to 10% of the pile diameter. Driven piles of comparable axial resistance are likely to mobilize the tip resistance at a smaller vertical displacement due to the inherent preloading at the tip that occurs during installation. Consequently, the load-settlement curve from a load test of a CFA pile may appear somewhat softer than that of a typical driven pile, and methods used to interpret ultimate load resistance from load tests on driven piles could be conservative for CFA piles.</p><p>According to Brown et al. (2007), the results of a test pile installation and testing program should be used to:<br><ul> <li>Establish target drilling penetration rate(s) for the various subsurface conditions on the site</li> <li>Establish pressure/volume relations for placement of grout/concrete. The grout factor (i.e., ratio of the volume of grout/concrete actually used to the theoretical volume for the specified pile size) that is calculated on the test pile(s) ±7.5% should be used for the installation of the production piles</li> <li>Establish target values for torque and crowd force for displacement or partial displacement piles</li> <li>Establish mix design parameters such as grout flow, necessary admixtures, etc.</li> <li>Evaluate design correlations of side and base resistance with the site specific soil parameters</li></ul></p></p>