Technical Support for SDDOT's Pile Load Testing Program
Developing an extensive database of field test results on deep foundation piles to improve design methods.
In October 2007, the Federal Highway Administration mandated using Load Resistance Factor Design (LRFD) methodology for all federally funded transportation infrastructure projects. Static and dynamic load testing as well as resistance factor calibration were required so that greater efficiency and consistency with the deep foundation design process were realized.
RESPEC assembled a qualified team to perform a work plan for the South Dakota Department of Transportation (SDDOT) that included suggesting a test matrix that targeted pile types and soil conditions common to the state. After sufficient data were collected, a probabilistic analysis was performed to recalibrate resistance factors using SDDOT methodologies. Using the expended database, RESPEC evaluated the applicability of several methods to predict pile-bearing capacity and developed a database of unit-side and tip-resistance values that are specific to South Dakota soils. Strain gage data along the length of the piles were used as well as the t-z method to enhance predictions of the load settlement curves for deep foundation piles.
This type of analysis provides unit-side and tip-resistance values for different soil types along the length of the pile and enhanced settlements to help interpret the failure load of the static load test. This data point is critical to implementing deep foundation design in accordance with the LRFD specifications.