Discussion of ‘Interpretation of Augered Cast in Place Pile Capacity Using Static Loading Tests’-Article

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Chen and Kulhawy compare their database of 56 ACIP pile load tests with the database used by Stuedlein and colleagues. Their dataset covers a broader range of pile dimensions and depth ratios, and both datasets concern piles in cohesionless soils.<br /><br />They discuss how pile slenderness affects interpretation. When the depth-to-diameter ratio (D/B) exceeds about 20–25, the initial load–displacement slope is similar to the elastic compression slope, so Davisson and slope-tangent-in-compression (STC) interpretations are comparable. At lower D/B, the elastic slope is steeper than the initial slope, which can make the Davisson interpreted load artificially low; the discussers recommend STC instead.<br /><br />The authors endorse plotting test data using Davisson’s recommended graphing scale and caution against smoothing the observations, which can obscure important features. The L1–L2 method identifies the elastic limit (L1) and interpreted failure threshold (L2) from the three regions of the load–displacement curve. Reliable identification of L2 generally requires data extending beyond that point.<br /><br />Chen and Kulhawy question several L1–L2 results reported in the original study. In multiple cases, the reported L2 load is below or nearly equal to Davisson or STC loads, contrary to their experience; they suggest data problems or misinterpretation. Across prior studies, L2 is typically about 15–25% above the Davisson or STC load. They recommend using this relationship cautiously to estimate L2 when tests do not reach sufficiently large displacements. Overall, they consider L1–L2 a useful, straightforward method when data quality and plotting are adequate.

Keywords

ACIP pile load tests

Chen and Kulhawy

Stuedlein database

cohesionless soils

pile slenderness

D/B ratio

Davisson interpretation

STC method

L1-L2 method

load-displacement curve