Representative criteria are examined to evaluate the “interpreted failure load” or “capacity” of rigid drilled shaft foundations under lateral loading. Field lateral load test data are used for this analysis, consisting of both drained and undrained databases. It was found that a hyperbola describes the load–displacement data well and that the normalized undrained curve is stiffer, higher, and more sharply curving than the drained curve. The initial elastic region ends at approximately 1%B (where B is the shaft diameter),which represents serviceability limit state (SLS) conditions. The final region begins at about 4%–5%B, which represents ultimate limit state (ULS) conditions. Also, the QL method is most appropriate for interpreting the “failure load” because it is the only method that incorporates actual soil-shaft failure mechanisms as part of the interpretation, is the least variable, and has the lowest coefficient of variation (COV). Further detailed recommendations are given for assessing the load test data.
Evaluation of interpretation criteria for drilled shafts with tip post-grouting