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

Article

Pdf Summary

The paper evaluates methods for interpreting failure loads from static loading tests on augered cast-in-place (ACIP) piles. Because different interpretation methods can produce substantially different capacities, the authors compare methods cited in the 2012 International Building Code (IBC) with other approaches, considering both interpreted load and associated displacement.<br /><br />The analysis uses 36 ACIP pile load tests in predominantly cohesionless soils. The Davisson Offset Limit (DOL) method served as a comparison baseline. On average, the modified DOL (MDOL), Butler–Hoy Criterion (BHC), Chin–Kondner extrapolation (CKE), and Hansen 90% Criterion (90C) produced capacities about 21%, 44%, 71%, and 83% higher than DOL, respectively. The BHC also generally required less extrapolation than the 90C method.<br /><br />The authors conclude that the original DOL method is inappropriate for ACIP and other drilled foundations. It was developed for driven piles and relies on assumptions about pile stiffness and toe behavior that do not fit cast-in-place piles. The 90C method can yield higher capacities, but often requires substantial extrapolation, making its reliability dependent on test data and subsurface conditions. The BHC is considered the most suitable IBC-approved method because it is systematic, comparatively objective, and provides more efficient capacity estimates without usually requiring extensive extrapolation.<br /><br />The paper emphasizes that pile displacement matters alongside interpreted capacity. Larger displacements at an estimated failure load do not necessarily imply unacceptable structural performance, since design factors reduce working loads and settlements. Practitioners should conduct tests to sufficiently large displacements, carefully assess geological conditions, and avoid relying on extrapolated capacities where soil layers or groundwater conditions could limit pile resistance.

Keywords

augured cast-in-place piles

ACIP piles

static loading tests

failure load interpretation

Davisson Offset Limit

Butler-Hoy Criterion

Chin-Kondner extrapolation

Hansen 90% Criterion

pile capacity

load test displacement