Load Transfer Behaviour of Instrumented Jet Grouting Self-drilling Anchors

Grouted anchors are one of the most efficient geotechnical systems to transfer tensile force from the structures to the ground. Recent technological developments have introduced solutions aimed at simplifying installation procedures while maintaining very high load capacity. Among these, jet-grouting self-drilling anchors combine hollow steel bars with high-pressure injection, allowing the installation without temporary casing and the formation of large-diameter foundations. However, the load-transfer mechanism along the foundation is still not fully understood, particularly when the foundation length exceeds the traditional limit of 10–12 m. This paper presents the results of full-scale pull-out tests performed on jet-grouting self-drilling anchors instrumented with strain-gage sensors distributed along the reinforcement, aiming at improving the understanding of the load transfer mechanism in anchors of different lengths and applied loads. In addition, one anchor was instrumented with a distributed fiber optic sensing (DFOS) system, providing quasi-continuous strain measurements that complemented the local strain-gage readings. These results highlight the strong concentration of load transfer near the top of the bonded length and demonstrate the potential of distributed fiber optic sensing for capturing the detailed load transfer mechanisms in grouted anchors.