Abstract
Deep displacement monitoring of rock and soil mass is the focus of current geological hazard research. In the previous works, we proposed a geophysical deep displacement characteristic information detection method by implanting magneto-electric sensing arrays in boreholes, and preliminarily designed the sensor prototype and algorithm of deep displacement three-dimensional (3D) measurement. On this basis, we optimized the structure of the sensing unit through 3D printing and other technologies, and improved the shape and material parameters of the permanent magnet after extensive experiments. Through in-depth analysis of the experimental data, based on the data query algorithm and the polynomial least square curve fitting theory, a new mathematical model for 3D measurement of deep displacement has been proposed. By virtue of it, the output values of mutual inductance voltage, Hall voltage and tilt measuring voltage measured by the sensing units can be converted into the variations of relative horizontal displacement, vertical displacement and axial tilt angle between any two adjacent sensing units in real time, and the measuring errors of horizontal and vertical displacement are tested to be 0–1.5 mm. The combination of structural optimization and measurement method upgrading extends the measurement range of the sensing unit from 0–30 mm to 0–50 mm. It shows that our revised deep displacement 3D measuring sensor can better meet the needs of high-precision monitoring at the initial stage of rock and soil deformation and large deformation monitoring at the rapid change and imminent-sliding stage.
Highlights
Geological disasters refer to rock and soil mass sliding accidents that damage ecological environment resources and seriously threaten human life and property under the influence of natural or human factors, including collapse, landslides, debris flows and so on [1,2,3,4,5,6]
A new mathematical model for 3D measurement of deep displacement has been proposed, which is based on data analysis-contour query and polynomial least-squares curve fitting. By virtue of this measurement model, the output values of mutual inductance voltage, Hall voltage and tilt measuring voltage measured by the sensing units can be converted into the changes of relative horizontal displacement, vertical displacement and axial tilt angle between any two adjacent sensing units in real time
Our research shows that the deep displacement of rock and soil mass can be accurately measured by using mutual inductance effect and Hall effect synthetically
Summary
Geological disasters refer to rock and soil mass sliding accidents that damage ecological environment resources and seriously threaten human life and property under the influence of natural or human factors, including collapse, landslides, debris flows and so on [1,2,3,4,5,6]. It is worth stressing that in recent years a new method of deep displacement measurement based on integrated sensing of electromagnetic measurements has been proposed, and the corresponding two-dimensional and three-dimensional measurement sensors have been developed, which have the following features: (1) With the flexible array structure design of sensing unit, each sensing unit can slide freely with the surrounding rock and soil mass, and the deformation coordination is good.
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