Abstract:
Integrity testing of drilled shafts through non-destructive methods has become commonplace in the industry. Many test methods are available and established, each having their own individual strengths and limitations. However, shaft acceptance should not be based solely on these test results. When integrity testing raises a concern or indicates a potential anomaly, the shaft may still be capable of performing as designed. All available installation information and test results should be considered.
When further investigation is warranted, there are several options to provide additional information for consideration of shaft acceptance. Common methods include additional testing utilizing alternate methods, concrete coring, or an engineering analysis with stated assumptions. A less common option is to perform a full-scale load test on the shaft in question to evaluate the ability of the shaft, as installed, to carry the structural loads. This paper will discuss two case histories where load testing was performed to support shaft acceptance where anomalies were indicated in multiple integrity testing methods.
Two county road bridges in close proximity and being constructed in the same timeframe were designed to be supported by drilled shaft foundations. The specifications required one shaft at each abutment be tested using Thermal Integrity Profiling (TIP). The TIP results indicated significant anomalies at the base of each shaft. The contractors and owners agreed to perform dynamic load tests to evaluate the load carrying ability of the shafts as installed. Prior to dynamic testing, Pile Integrity Testing (PIT) was also performed on each shaft. This paper will discuss and compare the multiple test type results for the shafts on these projects. The advantages and limitations of using this approach will be presented so others can evaluate the suitability of this testing option for foundation acceptance on future projects.