The Development Of Magnetoresistivity Receiving Prototype System Based On Grounded Wire Source

Dam construction in China flourished in the last century with the rapid development of water conservancy and hydropower in China.However,with the passage of time,dam leakage and dam-break events occur from time to time during the flood season.This was mainly due to the backward construction conditions at that time and the inevitable damage to the hydrological environment such as prolonged river immersion,rain erosion and natural weathering.These incidents have caused very serious harm to China's socio-economic development and the safety of people's lives and property.Therefore,it is very important to check the leakage of the dam.At present,the leakage detection of dykes in China is usually copied from other geophysical detection methods.As a result,some detection equipment is affected by factors such as the terrain environment,which causes problems such as inaccurate measurement results and low detection efficiency.In view of the above problems,this paper designs a magnetoresistivity receiving prototype system based on grounded conductor excitation source.The magnetoresistance detection method has been widely used in ground,air and ocean detection in the early days.With the continuous in-depth study of scholars from various countries in recent years,Willowstick applied the MMR detection method to the detection of dam leakage and achieved considerable detection results.This method mainly detects the priority flow path of groundwater by the difference in conductivity between the underground seepage flow path and the background material.By placing transmitting electrodes on both sides of the dam and injecting a low-frequency sinusoidal AC signal of a certain frequency,the conductivity of the leakage location is lower than that of the non-leakage location due to the leakage,and the leakage location becomes the priority flow path for current.By using a high-precision magnetic sensor receiving system to measure the magnetic field distribution above the dam body,the specific location of the dam leakage can be obtained by inversion.Due to the advantages of less impact on terrain and environment and higher detection efficiency,this method is suitable for dam leakage detection under complex conditions.At present,this method is rarely studied in China,and more attention is paid to the theoretical inversion research of this method.The instruments used for detection are mostly imported from abroad.This paper intends to design a magnetoresistivity receiving prototype system based on grounded conductor excitation source.The main research works in this paper are as follows:1)Firstly,the basic principle of the magnetic resistivity detection method is introduced,and a simulation model of the magnetic resistivity detection method in the application of dam leakage detection is established.The performance indicators of the instrument designed in this paper are put forward through the simulation results,which provides a reference for the later design.2)Then,the working principle of the hollow coil sensor is introduced.The influence of the sensor structure and the winding mode,the number of turns and the area of the coil on its signal-to-noise ratio and sensitivity is further analyzed.Finally,various parameters of the sensor are determined.According to the signal characteristics and design requirements of the sensor,a low-noise preamplifier circuit was designed to match it.By analyzing the noise floor of the sensor,the pre-operational amplifier is selected to reduce the noise floor of the sensor.Aiming at the problem that the three coils of the three-component coil sensor are not orthogonal,a three-component correction method based on the ellipsoid model is given in this paper to reduce the detection error of the total magnetic field due to the installation error.Furthermore,a high-precision signal conditioning circuit and a corresponding power circuit are designed to improve the signal receiving amplitude and anti-saturation capability of the system.In order to facilitate field operation and data recording,the GPS module was selected to record the collected time,latitude and longitude information in real time.In order to ensure that the sensors collect the attitude uniformly,an attitude acquisition circuit is designed to measure and store the attitude data.3)A suitable A / D acquisition card was selected for data acquisition.At the same time,the host computer software was written based on Windows system to control the system and display and save the collected data in real time.4)After the design is completed,the performance indicators of each part of the system are tested first.The test results show that the measurement range of the designed system sensor meets the signal amplitude requirements of the MMR detection.The nonorthogonal angle error of the designed three-axis sensor can be controlled within the ideal range.Then,a simulation detection experiment of priority flow path was carried out in the laboratory,which verified the effectiveness of the instrument for detection of priority flow path.Finally,a field verification test was performed using the designed receiving system,and the measurement results verified the effectiveness and practicability of the instrument in the field.