Wellerson Bastos, Marcos Pimenta Filho, Luiza Almeida, Marina Ferreira & Mauro Santos Junior


monitoring, visual inspections, and electromechanical equipment testing. Instrumentation-based monitoring relies on devices such as vibrating wire piezometers (VW piezometers) to measure critical parameters, including pore pressures, displacements, and water levels. Visual inspections detect physical anomalies that are observable by sight, while electromechanical tests ensure the proper function of critical components, such as reservoir gates and valves. Effective monitoring requires an understanding of the primary failure modes to which dams are susceptible, as outlined by [2]


and [3] . These modes include overtopping (caused by excessive reservoir


levels), internal erosion (loss of material due to seepage), liquefaction (loss of soil strength due to increased pore pressures), and slope instability (sliding of soil masses driven by elevated pore pressures). Piezometric monitoring is directly associated with slope instability, where measurements indicate increased interstitial pressures that could compromise slope stability. It is also indirectly linked to liquefaction detection and the identification of hydraulic gradients that signal internal erosion. VW piezometers are recognized for their robustness, precision, and long-term durability, making them indispensable in dam monitoring, particularly in conditions where manual readings are impractical or where structures experience high dynamic loads. Their ability to transmit data over long cables without significant signal degradation further enhances their utility in remote or large-scale installations. However, the accuracy and reliability of VW piezometer readings depend on adherence to best practices during installation, operation, and maintenance, as recommended by manufacturers such as Geokon[4]


, Encardio Rite[5] , RST Instruments[6] , Geosense[7] , Soil Instruments[8] . The “fully grouted” installation method, highlighted by[9], has gained prominence for enabling the placement of multiple


sensors along a single borehole, thereby enhancing spatial data resolution, particularly in low- permeability soils. Beyond installation, several technical procedures are critical for obtaining accurate measurements.


These include verifying sensor condition, ensuring proper saturation of the porous stone, inspecting electrical parameters, and correctly applying frequency-to-pressure conversion formulas. Initial zero readings, taken after the sensor reaches thermal equilibrium, provide a baseline for subsequent data and must be recorded before the final installation at the monitoring point. Additionally, correcting for environmental variables, such as temperature and barometric pressure changes, is essential to avoid misinterpretation of data due to frequency deviations[10]


. Given the complexities involved in both operating and interpreting VW piezometer data, this article


aims to systematize the key technical aspects and highlight best practices. The structure follows a logical and didactic progression: it begins with the physical principles underlying VW piezometer operation, a description of essential components, and their influence on performance. It then addresses sensor preparation steps, such as porous stone saturation and initial zero readings, before discussing manufacturer-specific correction equations and their adaptation in automated and manual data acquisition systems. Lastly, diagnostic tools for identifying errors and optimizing monitoring system performance are presented. By integrating these considerations, the article seeks to provide a comprehensive understanding of the operational nuances of VW piezometers, aiming to mitigate common errors and enhance the reliability of geotechnical monitoring programs for dam safety.


106 | Dam Engineering | Vol XXXIII Issue 3


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