Interpretation of augered cast in place pile capacity using static loading tests

Abstract

Instrumented static loading tests present an effective tool for appropriate engineering of piled foundations. Whether instrumented or not, considerable effort can be expended to determine the interpreted failure load developed during the loading test, and the determination of an appropriate capacity is often subject to regulatory review and discussion, which may be complicated by the large number of interpretation methods available and the large range in interpreted capacities that could result. This paper focuses on the differences in the interpreted failure load for augered cast in place (ACIP) piles and seeks to determine which methods are suitable and which methods are inappropriate for the interpretation of ACIP piles. First, a review of various capacity interpretation methods is provided with emphasis on those methods cited in the International Building Code (IBC, 2012). Then, an ACIP pile case history database used to illustrate differences in interpreted capacity is described, followed by the presentation of the resulting differences. Recommendations for and against the use of several failure load interpretation methods are made. This paper emphasizes the importance of both the interpretation of the failure load as well as the consequence of a particular methodology on displacement -a critical performance measure.

Evaluation of Static Pile Load Test Results of Ultimate Bearing Capacity by Interpreting Methods

“…In comparison, the results indicated that Brinch Hansen 80% method is the most accurate method among extrapolation methods in determining the failure load. The term ultimate failure of the pile is inappropriate to refer to continuous settlement under constant load, according to Stuedlein [11]. Therefore, the summary of the study emphasized the adoption of interpretation methods in determining the failure load.…”

“…Then, the 15 methods mentioned above were applied to each pile. Finally, the final bearing capacity was obtained with the specific settlement of each pile, where both load and settlement are done according to ASTM D 1143 [11].…”

State of the Art Dynamic Load Testing of ACIP Piles in the Americas

“…Stuedlein et al [1] discuss the challenges associated with the determination of "capacity" or "failure load" from static load tests. The authors argue that the most significant source of differences in the interpreted capacity from static load tests stems from the number of methods available for the interpretation of the static load test data.…”

Reply to the discussion by Flynn and McCabe on “Statistics of model factors in reliability-based design of axially loaded driven piles in sand”

“…The results indicate that the measured resistances from the L 1 -L 2 method are generally higher than the results from the slope tangent method. It has been recognized by Kulhawy and Chen (2005), NeSmith and Siegel (2009), and Stuedlein et al (2014) that the slope tangent method underestimates the ultimate pile axial Fig. R3.…”