Evaluation of Piles' Ultimate Capacity utilizing Direct CPT Methods Considering Consolidation and Aging Setup-PPT Presentation

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The study evaluates methods for estimating the long-term axial capacity of existing piles, particularly bridge piles affected by scour. Pile resistance can increase over time through two processes: consolidation setup, as excess pore pressure dissipates, and later aging, which increases soil strength, stiffness, and pile–soil interface resistance. Accounting for these gains may improve assessments of piles that have been in place for decades.

Researchers developed setup factors from test-pile and literature databases. For clay, the average consolidation setup parameter was <strong>Ac = 0.53</strong>. Aging parameters were <strong>Ag = 0.23 for clay</strong> and <strong>Ag = 0.16 for sand</strong>. These models were combined with eight direct CPT-based pile-capacity methods. Predictions were evaluated against instrumented pile tests and measurements from an existing bridge.

The CPT methods combined with the consolidation model generally underestimated clay-layer side resistance at the end of pore-pressure dissipation. After applying the aging model, predictions improved substantially. Across the eight methods, predicted-to-measured side-resistance ratios ranged from 0.76 to 1.29, while total-capacity ratios ranged from 0.85 to 1.20. The <strong>Philipponnat and UF methods</strong> gave the most accurate estimates of total resistance in the bridge evaluation.

The findings indicate that significant capacity gains can occur after consolidation is complete, and that incorporating both consolidation and aging is important when assessing long-term pile capacity. Ignoring these effects may be conservative, whereas using setup models with CPT-based methods can support more realistic evaluations of in-place piles.

Keywords

pile capacity

axial resistance

scour

bridge piles

consolidation setup

aging effects

CPT methods

side resistance

soil strength gain

long-term capacity