Evaluation of Pile Load Testing State of Practice for ALDOT Projects
Type of DegreeMaster's Thesis
Civil and Environmental Engineering
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A database of driven piles taken from archives of the Alabama Department of Transportation (ALDOT) was created for the purpose of evaluating the pile load testing state of practice for ALDOT. The dataset was derived from driven piles on ALDOT projects from 1995 to 2021. The database consisted of records from H-Piles, steel pipe piles, and prestressed square concrete piles. In this dataset, 81 piles possessed both static load test and high strain dynamic test (HSDT) data on the same pile. Of the HSDT, some piles were analyzed using CAPWAP (Case Pile Wave Analysis Program) and some were analyzed using iCAP. Analysis outputs consisted of end of drive (EOD), set checks (STCK - restrike within 24 hours of EOD), and beginning of restrike (BOR - restrike after 24 hours of EOD) data. There were 20 additional piles studied with static load test data only. All static load tests were further analyzed to observe the current state of static load testing practice. Many of the piles in this study were driven in the coastal plain region of Alabama. Currently, ALDOT commonly conducts static load tests and PDA-S and iCAP analysis on driven piles to predict ultimate capacity. A statistical analysis was conducted on the piles that had both static load test data and HSDT data to determine if ALDOT could rely less on static load tests and more on HSDT to determine ultimate capacity. If this were possible, it could potentially save ALDOT a tremendous amount of money and time, as static load tests are both expensive and time consuming. HSDT (both CAPWAP and iCAP) at EOD, STCK, and BOR were compared to the maximum load applied (MLA) during each static load test. It would have been preferred to compare a Davisson Failure criterion from each static load test to HSDT EOD, STCK, and BOR. Unfortunately, from the dataset gathered, only 18 out of 101 static load tests conducted on ALDOT projects reached Davisson failure criterion. In the current state of practice, ALDOT conducts static load tests on test piles to either two and a half times or three times the design load and does not typically load test piles to Davisson failure criteria. Because of this, the MLA from the static load test was used to compare to HSDT results. Because there was a mixture of piles having HSDT by both CAPWAP and iCAP, statistical tests were conducted to determine if there was a difference between CAPWAP and iCAP. In this dataset, there was no significant difference between CAPWAP and iCAP in their linear relationship with the MLA during the static load test. For the purposes of this analysis, CAPWAP and iCAP were considered equivalent. Overall, there was a significant predictor effect of HSDT on MLA at the endpoints of EOD, STCK, and BOR as assessed by simple linear regression. However, it does not appear that HSDT is a surrogate or substitute for MLA across all subsets of the dataset examined. Further research will be required to better understand the complex relationship between dynamic and static load testing.