Research on Structure Optimization and Measurement Method of a Large-Range Deep Displacement 3D Measuring Sensor

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. stage is characterized by cracks in the surface layer of rock and soil mass, followed by collapse [9]. Therefore, studying the deep displacement of rock and soil mass is more in line with the needs of disaster prevention and mitigation than the study of surface displacement. The deep displacement of rock and soil mass can reflect the dynamic stability of rock and soil mass more accurately and quickly, therefore it provides accurate, powerful data and theoretical support for early warning of landslides.However, the deep displacement measuring device must be buried deep underground, requiring the instrument to be strong, anticorrosive, convenient for installation, operation, long-distance signal transmission and so on. At the same time, the deep displacement monitoring environment is harsh and complicated, and there are problems such as no light, water seepage, corrosion, geotechnical shearing and extrusion, which can easily cause damage to the buried instruments. Therefore, compared with surface displacement monitoring, the development of deep displacement monitoring technology is relatively slow, and the types of deep displacement monitoring instruments that can be practically applied are obviously less and have poorer performance. At present, the global monitoring of deep displacement of rock and soil mass mainly includes borehole inclinometer, time domain reflection technology, Brillouin Optical Time Domain Reflection (BO...

Low-Power and Wireless Communication Research on Underground Displacement Three-Dimensional Monitoring System

“…In two adjacent coils, when the current in one coil changes, an induced electromotive force is generated in the adjacent coil, which is called the mutual inductance phenomenon. The principle of dual mutual inductance measurement proposed by our research group [ 11 , 12 ] is based on the application of the mutual inductance phenomenon. Figure 2 shows the principle diagram of dual mutual inductance voltage measurement.…”

“…However, these methods cannot achieve the monitoring of underground three-dimensional displacement of rock and soil mass and cannot truly reflect the evolution process of underground rock and soil mass. In recent years, our research group has integrated multiple magnetoelectric sensing mechanisms such as electromagnetism, mutual inductance, and magnetoresistance, combined with dual mutual inductance equivalent modeling, a flexible sensing array, and integrated sensing technology, to propose a new type of underground displacement remote monitoring system [ 11 , 12 ], which can automatically, in real-time, and accurately monitor the underground three-dimensional displacement of rock and soil mass. Through the study of the above literature, the advantages and disadvantages of existing underground displacement detection methods are shown in Table 1 .…”

“…The original system [ 11 , 12 ] used an RS485 bus to connect the ground management terminal and hundreds of sensing units for communication. If the 485 communication module of any sensing unit has failed for some reason, it will cause other sensing units to be unable to continue 485 communication.…”