The Modeling Research For Detecting Three-dimensional Underground Deformation Based On Sensing Method Of Magnetic Ring

Landslide is always induced by underground deformation, which is quitehazard to human community. At the same time, monitoring the undergrounddeformation is an important index of geotechnical instrumentation for detecting thelandslide. Thus it is necessary to utilize the real-time instrument to monitor thoseareas that would probably encounter the landslide. Also people could realize thesedisasters as early as possible.Nowadays, people use TDR coaxial, inclinometer and multi-point displacementmeter to detect the underground deformation. However, these devices could noteffectively reflect the three dimensional deformation of underground mass. Thus wepropose a new way to detect the3D underground deformation which based on HallEffect and sensing method of magnetic ring.According to the geological characteristics of the rotational landslide andtranslational landslide, this paper issues the measuring scheme: connecting all thecylindrical measuring units along with a common axis and burying them into thesubsoil with certain direction, the device could measure all the relative displacementbetween any adjacent units to reflect the deformation of underground mass.After installing the Hall sensor array, magnetic ring and PCB board into thecylindrical measuring unit, and establishing the cylindrical coordinate system, thisinstrument would indicate the distance of relative deformation of adjacent units, bycollecting output voltages and utilizing the special algorithm. At the meanwhile, thetrend of underground movement could be detected.In order to calibrate the Hall sensor, the author sets up the experimentalplatform and regularly changes the relative position between Hall sensor andmagnetic ring which are settled into the measuring unit. Resorting to the magneticfield distribution of magnetic ring, calibrating data and MATLAB, the contour linesof Hall voltage could be acquired. Thus, a new measuring module is proposed whichis comprised by four HALL sensor array. Each Hall sensor could output a certain voltage value, due to the incentives of magnetic ring in any position. And each valueof voltage could directly correspond to a contour with the same voltage value.Theoretically, the intersection of four contour lines reflects the coordinate point ofmagnetic ring. Due to the measurement error, this point could be achieved by methodof approximation. Depending on this, we could get relative spatial position of twoadjacent measuring units.3-Axis digital accelerometer could measure the axial angle of unit and directionof relative displacement of any two adjacent units.In the cylindrical coordinate system, the quoted error of R axis of magnetic ringcould be lower than8%; the quoted error of Z axis of magnetic ring could be lowerthan6%. Meanwhile, the measuring quoted error of axial angle of unit anddirectional angle of relative displacement of any two adjacent units would be nomore than0.11%. Thus measurement of relative displacement of two adjacent unitscould meet the actual requirements.