Reliability Analysis of load carrying capacity of Single Pile placed adjacent to existing Buried conduit or utility tunnel-Paper

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The study evaluates the reliability of estimates of pile-capacity loss when a single pile is installed near an existing buried pipe or utility tunnel. Because soil properties vary and are measured with uncertainty, the authors argue that deterministic capacity estimates alone may not adequately represent the confidence in the predicted reduction.<br /><br />The analysis combines finite-element modeling in PLAXIS 2D, the response surface method (RSM), and the First Order Second Moment (FOSM) reliability approach. PLAXIS models compare pile load–settlement behavior with and without a nearby conduit. RSM is then used to approximate the relationship between uncertain geotechnical inputs and the percentage reduction in pile capacity, enabling estimation of the reduction’s mean and standard deviation. The analysis assumes the input parameters are normally distributed and uncorrelated, and does not account for changes in soil properties caused by pile installation.<br /><br />The estimated mean capacity reduction is 15.92%, with a standard deviation of 2.95%. Using an assumed tolerable reduction of 33%—based on a factor of safety of 3—the calculated reliability index is 5.88, classified as “excellent” under the cited USACE guidance. The authors conclude that this workflow offers a relatively efficient preliminary way to assess uncertainty and support decisions about pile placement near buried infrastructure. They suggest it could also be applied to pile groups.

Keywords

pile-capacity loss

buried pipe

utility tunnel

reliability analysis

finite-element modeling

PLAXIS 2D

response surface method

FOSM

geotechnical uncertainty

pile settlement