PSI - Issue 64

Emilia Damiano et al. / Procedia Structural Integrity 64 (2024) 1628–1635 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. The laboratory setups: (a) inclinometer tube equipped with two NSHT prototypes; (b) NSHT test setup on a wind turbine wing.

2.2. In site setup At the end of 2022, a 40-meter-long DFOS-inclinometer was installed in an active slow-moving landslide in Southern Italy. In the site application, four faces of the inclinometer tube were equipped with the NSHT and a temperature cable. The sequence of the installation procedure is illustrated in Fig. 2. After drilling the vertical hole, the NSHT transducers are unrolled and fixed to the lower end of the inclinometer tube. Then, the inclinometer casing tube is progressively lowered down into the hole and the NSHTs are connected to it through rivets at a 1 m interspace. Once the positioning of the inclinometer is completed, backfilling with cement grouting is done. As for conventional inclinometer measurements, zero reading is taken after approximately 30 days. The use of NSHT facilitated the installation procedure, reducing the time and cost of the operation while safeguarding the DFOS from potential damages. Data were retrieved by using a commercial BOFDA interrogation unit ( FibrisTerre, Germany ) with a sampling and spatial resolution of 5 and 20 cm, respectively. The entire equipment reached an accuracy of +/-20  .

Fig. 2. DFOS-based inclinometer on-site installation phases: (a) NSHT transducer; (b) preparing NSHT transducers; (c) assembling NSHTs and temperature cable to the inclinometer tube; (d) installing the inclinometer in the hole; (e) detail photo during equipping and lowering of the tube.

2.3. Strain data interpretation for slow landslides DFOS-based inclinometers diverge from traditional ones by measuring strain within soil masses. Strain can be due not only to sliding but also to other phenomena like consolidation or swelling of clayey soil layers, dilation or