Observed Behaviour of Floating Composite Passive Anchors in Landslide Stabilisation through DFOS

Passive anchors are widely used for landslide stabilisation due to their adaptability and ease of installation, yet their in-situ mechanical behaviour remains difficult to observe and is often inferred indirectly from global slope response. This study investigates the behaviour of floating composite passive anchors instrumented with distributed fibre optic sensing (DFOS), with the aim of bridging the gap between assumed and observed performance. Two field applications are presented: an experimental test site where anchor activation was intentionally promoted, and a real stabilisation project characterised by low residual slope movements. High-resolution DFOS measurements allowed direct observation of strain localisation and its evolution along all the anchors length, providing insight into load transfer mechanisms and long-term sensor durability. The comparison between the two cases highlights the complementary role of distributed monitoring within an observational framework, supporting a more physically based interpretation of anchor performance and improved confidence in stabilisation effectiveness.