Estimation of Maximum Unit Side Resistance in Drilled Shaft Foundations from Partially Mobilized Load-Displacement Data-PPT Presentation

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This study develops a method to estimate maximum unit side resistance in drilled shaft foundations when load-test data show only partial mobilization. The goal is to improve estimates of shaft resistance for research on diameter-related scaling effects.<br /><br />The dataset included 145 load tests from multiple states and construction methods. Researchers characterized 454 unit side-resistance curves by predominant soil type—cohesive, cohesionless, or mixed—and used the Double Tangent Method to estimate each curve’s mobilization ratio. Only 52 curves (11.5%) showed fully mobilized resistance; most were partially mobilized.<br /><br />Regression models were developed to predict maximum resistance from partially mobilized measurements. Models were assessed globally and by soil type, with construction method also considered. Comparisons between computed and measured maximum resistance showed strong agreement, with high coefficients of determination across soil categories.<br /><br />The models were then applied to partially mobilized data representing about 80% of the load-test dataset. Predictions showed a reasonable increase in estimated resistance, with limited variation and low error. The researchers report that the models were also validated using two independent load-test datasets.<br /><br />Overall, the results suggest that the proposed approach can estimate maximum unit side resistance from incomplete load-displacement records, reducing reliance on tests that achieve full mobilization.

Keywords

drilled shaft foundations

unit side resistance

partial mobilization

maximum resistance estimation

load-test data

Double Tangent Method

regression models

soil type classification

diameter-related scaling

load-displacement records