At long last, the report for the NCHRP micropile study performed by Erik, Dan D., and Andy is published. The report, Reliability-Based Geotechnical Resistance Factors for Axially Loaded Micropiles, is the result of a considerable research effort that aims to rework AASHTO’s micropile design methods. Highlights of the research tasks are listed below.
- Compile a database of micropile load tests and organize the database by micropile type and ground conditions.
- Develop new presumptive and predictive models for micropile design. The presumptive models are based only on micropile type and ground condition; the predictive models further consider soil or rock strength.
- Calibrate probabilistic resistance factors for micropile design based on presumptive and predictive models, and for designs based on site-specific load tests. If adopted, the resistance factors for designs based on load tests would be the first for AASHTO to be based on probabilistic calibration rather than fitting to historical practices.
The report can be downloaded for free from TRB’s website: