PSI - Issue 84

Lorenzo Di Taranto et al. / Procedia Structural Integrity 84 (2026) 1007–1014

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2.1. Inclinometer Monitoring

Experimental evidence derived from boreholes instrumented with MEMS (Micro-Electro-Mechanical Systems) inclinometer chains provides significant data for characterizing the slope kinematics. The monitoring system consists of Inclinometer 1, located upslope, reaching a depth of 40 m below ground level (b.g.l.) with sensors installed at 1 meter intervals, and Inclinometer 2, located downslope of the infrastructure, which reaches a depth of 60 m b.g.l. with a sampling interval of 1 meter down to -30 m and 5 meters for the remaining section (Fig. 3). Analyses conducted for the year 2024, taking January as the reference baseline reading, suggest the presence of a deep-seated instability phenomenon characterized by the coexistence of two or more active slip surfaces. Specifically, measurements from vertical 1 (upslope) highlight a main slip plane located at approximately 26 m b.g.l., with a cumulative displacement of 5 mm primarily concentrated in the October–December quarter. Concurrently, an additional deformational horizon is identifiable at a depth of about 10 m b.g.l., with displacements of approximately 1 cm recorded during the same period. This kinematic behavior exhibits significant spatial variations downslope: data from Inclinometer 2 identify a slip surface at a depth of approximately 26 m b.g.l., where the deformational activity is markedly more evident, with cumulative displacements reaching 1.8 cm over the entire year.

Fig.3. planimetric layout of inclinometers, piezometers, and cross-sections; (b) 2024 incremental inclinometer displacement plots for inclinometers 1 and 2 (60 m depth), with the baseline reading (Reading 0) in January 2024.

2.2. Piezometric Monitoring Piezometric monitoring was conducted using piezoresistive cells with continuous recording along the same boreholes instrumented with inclinometers. These sensors were arranged at four depths for each vertical: -7 m, -12 m, -18 m, and -28 m below ground level (b.g.l.). Specifically, borehole 2 (Vertical 2), located near the right abutment of the viaduct, exhibits pore water pressure dynamics that are highly differentiated according to the installation depth. Data from the sensors at the shallower horizons (-7 m and -12 m) show a general downward trend in pressures over time. This behavior suggests a progressive reduction of the hydraulic head in the upper levels, likely related to the