| China is currently one of the most serious mine water disaster countries in the world. For a long time, coal mine water disaster has restricted the development of safe production of coal mining industry and brings very heavy damage to the lives and property of the State and the people. In addition, the collapse column and fault although not as flood that caused great damage to life and property, but not in the coal lane tunneling process to detect its existence, it will cause damage to the tunneling equipment caused economic losses, and also to create difficulties for maintaining roadway roof, affecting the normal production efficiency.To explore in front of the coal roadway driving working face with collapse column and fault is very important to ensure safe and efficient production of coal roadway, too.Therefore, in the process of coal roadway driving, detecting if there are water-conducting or-bearing, collapse column and fault fastly, accuratly in a certain range is an important task to ensure safe production of coal mine. Currently, coal roadway advanced detection methods are drilling and geophysical prospecting method. Drilling method is a kind of traditional method, with drilling equipment to Drill a depth detecting hole and coring. The water-conducting or –bearing structure, collapse column and fault are located accuratly by observing and analysising the coring. The inadequacies of this approach are: equipment complex, long construction time, detecting slow and short distance, encounting catastrophic water may cause water inrush accidents, the detection result is "a peephole view", not "face". Geophysical prospecting method is mine geophysical exploration short for all kinds of geological exploration especially in the coal mine underground mining space using the physical properties of the medium to detecting somethings. Compared with the method of drilling, mine geophysical prospecting method has the advantages of economic, efficient, non-destructive, large detection range and so on. Comprehensive tunneling geophysical prospecting technology in coal roadway, therefore, have been many scholars focus on topic and research direction.At present, researched relatively deeply and have some application cases in coal roadway, there are four geophysical methods: DC mine advanced detection technology, mine transient electromagnetic method, mine geological radar advanced detection technology, mine seismic wave technology. But special working environment of coal roadway and coal mine special requirements on the observation system and equipment brings technical bottlenecks, many interference factors, data acquisition and data interpretation difficult and many other advanced detection problem for geophysical prospecting technology. It also makes the existing geophysical methods always exist certain defects.After analyzing the summary of the principles of current geophysical methods, the China University of Mining and Technology(beijing)puts forward the focusing dual frequency induced polarization(IP) advanced detection method in coal roadway tunneling. The technology is organic combining the dual frequency induced polarization method having strong anti-interference ability and widely used to detecting metal ore on the ground, with focusing DC electric method having a large detection distance.This paper focuses on the research of Forward-inversion Model and Signal Transmitter for Dual-frequency Induced Polarization Advanced Detection Method of Comprehensive Tunneling in Coal Roadway. The research of focus double-frequency induced signal transmitter engineering prototype is completed. The mathematical model of dual-frequency and focus dual-frequency IP advanced detection method is established. The inversion method of key target parameters is proposed. The characteristics of different pole scheme are analysised. The performance of signal transmitter engineering prototype and the theoretical analysis results are verified by the laboratory simulation test. The main results and conclusions of this paper are as follows:(1) developed the focus induced signal transmitter prototype of advance detection in coal roadway tunneling on dual frequency IP methodIn view of the status quo that the lack of mining focusing on dual frequency induced signal transmitter restricts the development and application of dual frequency and focus dual-frequency IP detection technology in the field of advanced detection in coal roadway, the focus induced signal transmitter prototype of advance detection in coal roadway tunneling on dual frequency IP method is developed. Prototype can output up to five channels to transmit doul-frequency modulation square wave induced signall. It can meet the need of the doul-frequency and focus doul-frequency IP advanced detection. The prototype uses a switching power supply with isolation function, constant current circuit, secondary constant current circuit, linear isolation circuit, communication and modulation signal isolating circuit circuit, the circuit ensures the five outputs single transmit to the same medium adjustability and stability and accuracy. In addition, according to the requirements of electrical equipment for coal mine safety, all the input and output ports in the prototype of have been developed with isolated and double over current, over voltage protection circuits. The prototypes can stimulate a significant induced polarization effect in the medium by test in the lab and the prototype through all testing in coal testing center made explosion-proof certificate.(2) Mathematical model of advanced detection in coal roadway with the dual frequency induced polarization method is studied, using the model the forward and inverse relations is analysised.Basing on the potential field of point source and medium resistivity cole-cole mode, analytical mathematical model is established. The model indicates the relationships between direct measurement parameters and the key parameters—geological anomalous body size and safety distance.Through the analysis of the model from the principle it points out that the dual frequency IP method can eliminate the influence of roadway cavity and occasional disturbances factors on the detection results, and has the advantages of strong anti-interference ability. By using the mathematical models, the forward and inverse relationships between the directly measured parameters and advanced detection target key parameters—the size and the safety distance of disaster water-conductoring or water-bearing structure, subsided columns and faults of three kinds of coal roadway common advance detection targets. A inversion method to calculate the size and safety distance of disaster water-conducting and bearing body, subsided columns and faults basing on directly measurement parameter percent frequency effect(PFE) is proposed.(3) Mathematical model of advanced detection in coal roadway with the focus dual frequency induced polarization method is studied, using the model the forward and inverse relations is analysised.Basing on the electric field superposition principle, it establishes a frequency-domain analytical mathematical model of point potential for three- and five-pole focusing measuring conditions. The ratio of shielding current and main current and the forward and inverse relationships between the directly measurement parameter PFE%-R and the size a safety distance d and inclination θ1 of disastrous water-conducting or bearing structure, collapse column and fault,are analysised by the proposed model. Analysis results indicate: the better current ratio is 1:1 in theroy; by two poles running device, the induced current forcus is better than induced current unforcus in response for abnormal structure and both of them can ignore the influence of inclination θ1; Five poles focusing is more sensitive about the thickness a, safety distance d of water-conducting or bearing structure, collapse column and fault than tripolar focusing and in the detection range, there are the following rules dfive poles focusing and two running>dthree poles focusing and two running>dno focusing and two running; Basing on the conclusion of forward analysis, the thickness and safety distance of water-conducting or bearing structure and collapse column can be calculate by the directly measures parameters PFE%-R.(4) a comparative analysis of the different Electrode arrangement schemes of the dual frequency induced polarization method in the advanced detection of different geological anomalies.Different Electrode arrangement schemes such as no current focus with two or three poles running, three poles focus with two or three poles running and five poles focus with two or three poles running etc. are researched. And the result shows that the parameters of water-conducting or –bearing structure PFE%-R is increase at first and then reduce existing the maximum point; the parameters of collapse column PFE%-R is reduce at first and then increase existing the minimum point; the parameters of fault PFE%-R is always reduce arossing the zero point in all detection programs. So we can determine the type of abnormal body basing on the PFE%-R data by the result. In detection programs, focus advanced detection of abnormal response is more sensitive than non focus, and on the size and security anomalies distance with high resolution. Inaditionally, detection depth of induced current focus is large and the risk of losing the inversion of information is relatively small.(5) carrying out laboratory simulation test, through the test to detect focus dual frequency induced signal transmitter engineering prototype, and verify mathematical model and the theory conclusionIn model test use earth to simulate the coal, dig groove and tank in the ground down and then filling in different electrically polarizable medium to simulate typical coal roadway and geological anomalies. The function test results show that the prototype function achieves the expected design requirements. The simulation results not only prove the correctness of the theoretical analysis and the reliability of the proposed method in the previous chapters but also indicate that under the same focus pole condition, three poles running scheme has strong anti-interference ability; with the same measurement program without focusing, five-pole and three-pole focus programs in turn, enhance its capability of anti-jamming. |
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