Evaluation of uplift interpretation criteria for drilled shaft capacity

Representative interpretation criteria are examined to evaluate the capacity of drilled shaft foundations under axial uplift loading. A wide variety of uplift load test data are used, and these data are divided into drained and undrained databases. The interpretation criteria are applied to these load test data to establish a consistent uplift interpretation criterion. The results are comparable for both drained and undrained loading. In general, the undrained load test results show somewhat less variability than the drained results. Based on these analyses, the Q(L2), Q(0.5in), and slope tangent methods are the more reliable and consistent, and specific design recommendations for the interpretation of uplift drilled shaft load test are given, in terms of both capacity and displacement.