3D Measurement Method Of Underground Displacement Based On Hall And MR Effect

Landslide occurs frequently with enormous harm. There are variousmonitoring contents of landslide, and underground displacement monitoring is themost difficult one. It can intuitively reflect the deformation of the subsoil. Real-timedisplacement monitoring of potential landslide area plays a timely role in earlywarning.To monitor the deep displacement of slope, inclinometer buried in geologicaldrilling, multi-point displacement meter and TDR coaxial cable are used. Three mainmeasurement methods can not measure the three-dimensional changes of theunderground displacement. Therefore, this paper proposes a3D measurementmethod of underground displacement based on Hall and MR effect.Analysis the geological change of landslide movement, and select rotationallandslide, translational landslide and block slide to be measurement objects. Proposethe measurement scheme based on local geological structure invariance of slidingbody and outline model of3D displacement: connect all the cylindrical measuringunits along a common axis, and bury them in the subsoil; measure all the relativedisplacement between adjacent units to realize the whole subsoil measurement.Install the Hall sensors, magnet, MR sensor and shield in the cylindricalmeasuring unit, and establish the3D Cartesian coordinate system of measuringdevice. For the Hall sensor of measuring unit A and magnet of measuring unit B,subsoil deformation will change the relative position. Calculate the coordinates ofmagnet before and after geotechnical displacement, and the magnitude ofdisplacement can be calculated through geometric operation.Set up the experimental platform, and gradually change the relative positionbetween Hall sensor and magnet to calibrate Hall sensor. Based on the magnetic fielddistribution of cylindrical magnet and data analysis of MATLAB, contour lines andisosurfaces of magnetic flux density (Hall voltage)can be gotten. Three Hall sensorsin triangular distribution are uesd to compose the sensor array. To a magnet in thespace, every Hall sensor has a certain Hall voltage and corresponding isosurface. Three isosurfaces intersect at one point, and the three-dimensional coordinate of thepoint can be derived from the measurement algorithm.With the geomagnetic measurement using MR sensor and magnitudemeasurement, the direction of relative displacement between adjacent measuringunits can be measured. The measurement range of relative displacement can bedescribed by an irregular cylinder. The irregular cylinder is the public part of threecylinders based on the calibration data of Hall sensors.The measurement accuracy of3D coordinate measurement can be within±5%,and the measurement accuracy of geomagnetic measurement can be within±2%.Measurement of relative displacement meets the actual requirements.