Implementation Of Metallic Ore Goaf Detecting System Based On Time-domain Electromagnetic Method

The economic development demand for mineral resources is increasing,although the metal mineral resources in China is rich,but most of metal mines due to historical reasons there are complicated goaf,if there is a collapse of an unknown mined out area in the mining operation,it may result in serious safety accidents.So it is very important to explore the mined out area.In recent years,the application of time domain electromagnetic method is more and more mature both in theory research and instrument development,this method was successfully applied in mineral exploration,water resource exploration,military surveying and mapping direction,is a frequently used method of geophysical field,however,there is no large-scale application in the detection of mined out area.It is found that some researchers put forward the application of time domain electromagnetic method in the exploration of metal mine goaf,engineers have also used a variety of geophysical equipment tried,although the results have been achieved,but because of the lack of targeted use of the device,so the method does not scale applications.In order to verify whether the principle of time domain electromagnetic method is suitable for the detection of mined out area,Ansoft Maxwell 3D is used to construct the model of underground high resistivity sphere to simulate the mined out area,on the basis of the simulation analysis,the relation curve between the induced voltage and the measured point position is obtained.It can be seen from the curve that the existence of the high resistivity sphere is abnormal,which shows that the principle can play an important role in the exploration of mined out area.Therefore,in view of the characteristics of the metal mining area,this paper designs a metal mine goaf detection system based on time domain electromagnetic method.The system includes three parts: transmitter,coil and receiver.The transmitter consists of the transmitter timing control unit,the knob type parameter setting unit,the transient high power supply based on the large capacity capacitor,the high power H bridge unit based on the IGBT,the drive circuit unit and so on;The design requires that the 200 V emission voltage can be reached under the field conditions,and the key parameters such as emission time and acquisition time can be adjusted.The receiver includes two aspects of hardware and software.The hardware includes signal conditioning circuit module and the signal acquisition unit,using a combination of flat PC+ acquisition card to receive and collect the signal,and the realization of AD conversion;The receiver includes two aspects of hardware and software.The hardware includes signal conditioning circuit module and the signal acquisition unit,using a combination of Tablet PC and acquisition card to receive and collect the signal,and the realization of AD conversion;The software part of the Lab VIEW platform using the "producer consumer" programming model based on the design requirements to realize the "acquisition","stack","save" and other functions,After the parameter setting of the front panel is completed,the program begins to collect and display the waveform in real time.In order to reduce the interference of the noise,the received digital signal will be processed in the same way,and the data will be stored in the default path.After the prototype was completed,we conducted a series of tests in the laboratory and in the field.In laboratory tests,this system can work in various gear combinations,and the test of the instrument parameters were calibrated,bipolar pulse signal transmitter can transmit the maximum 200 V in the test,pulse width,frequency and other key parameters can be adjusted by the knob switch on the panel;The receiver can complete the 4 channel sampling with the 156 k sampling rate,and the sampling precision is 24 bits.The key parameters of the instrument meet the design requirements.In the field test,first of all,a measuring line is arranged in the area which is known to have underground mined out area,It can be seen from the inversion results that the received signal has a significant decline in the mined area.After the analysis of the experimental process and results,it is proved that the design of the metal mine goaf detection system has a strong function and reliability in the field exploration,it can be used to detect the mined out area of the underground 0-60 m inthe metal mining area,and has confirmed the positive correlation between the detection depth of the metal mined out area and the emission voltage.