A novel DFOS-embedded steel strand tendon ground anchor was developed with embedded fiber optic cables for strain measurement throughout the anchor cross-section. This unique cable configuration enables distributed
strain sensing (DSS) along the steel strand tendon, internal grout, and external grout during pull-out testing and long-term. A full-scale field test with four 60-ft (18.3m) ground anchors in mixed soil conditions was performed, with installation and pull-out testing in Antioch, CA. Varying grouting configurations were evaluated: with and without post-grouting. Two DFOS platforms: Optical Frequency Domain Reflectometry (OFDR) and Brillouin Time Domain Reflectometry (BOTDR) were demonstrated as suitable for ground anchor field monitoring. This novel approach enabled a detailed investigation of the tendon/grout/ground interaction mechanism and its effect on the strain transfer transition zone between the bonded and unbonded sections of the anchor. Looking forward, these findings will support future numerical modeling and ultimately transform the state of practice for resilient ground anchor design and construction.
