Critical aspects of using vibrating wire piezometers in geotechnical monitoring of dams: how to meet basic operating principles of the devices and avoid common errors that compromise monitoring


The linear approach simplifies field operations by reducing the complexity of data input, making the


process more efficient compared to polynomial equations, which require more constants for pressure calculation. This simplification facilitates sensor calibration and integration with monitoring systems without significantly compromising instrument accuracy in most applications. However, using instruments from different manufacturers with shared dataloggers or readout devices


requires adjusting the variable nomenclature and conversion factors to match the calibration settings of each piezometer model. The following equations (3.3 to 3.6) present the transformations between different piezometers, highlighting variations in the positioning of factors and the addition and subtraction operations adopted by different manufacturers.


Soil Instruments (Equation 3.3)[8] : (3.3) where:


• G: linear calibration factor (e.g. kPa/digit); • L0: zero reading taken during installation (in digits or Hz2


• Tk: thermal correction coefficient (e.g. °C/digit); • T1: current sensor temperature (°C); and • T0: initial reference temperature (°C).


RST Instruments (Equation 3.4)[17] : (3.4) where:


• CF: linear calibration factor (e.g. kPa/digit); • L0: zero reading taken during installation (in digits or Hz2


• Tk: thermal correction coefficient (e.g. °C/digit); • T0: initial reference temperature (°C); and • T1: current sensor temperature (°C).


Roctest (Equation 3.5)[15] : (3.5) Vol XXXIII Issue 3 | Dam Engineering | 113


/1000); • L: subsequent frequency readings taken in the field (in digits or Hz2 /1000);


/1000); • L: subsequent frequency readings taken in the field (in digits or Hz2 /1000);


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