HMT mining
Publish: 2021-04-11 05:04:58
1. mining subsidence area is also called goaf
goaf is proced under the surface by man-made excavation or natural geological movement; Empty & quot;, The existence of goaf makes the safety proction of mine face great safety problems, personnel and mechanical equipment may fall into the goaf and be injured
e to the lack of timely and effective backfill and grouting treatment in some places, the area of underground goaf in China is becoming larger and larger. Goaf changes and destroys the natural balance of the earth's surface and lithosphere, resulting in Goaf Collapse and other geological disasters
the collapse of goaf is caused by the goaf of ore body (layer) and the destruction of overburden. The mechanical balance of overlying rock above the orebody will be broken when the underground orebodies of various sizes are mined and mined out. Under the action of gravity and stress, cracks and fault displacement will occur. Groundwater will take advantage of the deficiency and leak into the goaf through cracks, which will accelerate the destruction of overburden, cause the movement of strata and surface, and finally form the Goaf Collapse Area
the collapse area will not only lead to the depletion of groundwater, the destruction of cultivated land, the deterioration of ecological environment, but also damage the local houses, the ground fissure deformation of roads, the construction difficulty and cost of major projects such as expressways, railways, airports and urban buildings e to the treatment of Goaf Collapse. In addition, the surface cracks will provide sufficient oxygen for the underground natural coal seam, the underground coal fire will weaken the roof pressure of the goaf, aggravate the caving, widen and lengthen the ground cracks, and finally form a vicious circle of "ground cracks fire area surface cracks"< Gravity exploration method is to use the mass loss or surplus of underground geological bodies to observe the gravity anomaly caused by them on the surface, so as to determine the distribution, size and boundary of underground geological bodies. The quality loss of goaf e to mining results in low gravity anomaly. When the goaf is well preserved, the low value resial gravity anomaly is formed. When the goaf collapses without water filling, the mass loss value remains unchanged, but the negative density value decreases and the influence thickness increases; When the water is filled, the loss mass is compensated to a certain extent, and the negative density value is reced. No matter what kind of situation actually exists in the goaf, the local resial gravity anomaly can be detected according to the general law. Using high density and high precision microgravity survey and proper data processing and interpretation methods, the area of goaf can be controlled. In order to improve the accuracy of interpretation, the digital terrain multi-slice high-precision geological reconstruction method and three-dimensional interpretation method are adopted< In the field measurement, all the electrodes are set on a certain interval measuring line, and then connected to the programmable multi-channel electrode converter with multi-core cable, so that the electrode layout can be completed at one time. In order to collect a large amount of data accurately and quickly, the electrode arrangement, electrode distance and measuring point can be quickly converted by program control. With the help of the electrical processing software, the collected data are processed and the results are illustrated, which makes the interpretation more convenient and intuitive. Based on the results of electrical resistivity tomography in goaf and inclined air shaft of a power plant, the application of electrical resistivity tomography in goaf and inclined air shaft is discussed. The results show that the two-dimensional measurement method of electrical resistivity tomography in goaf and inclined air shaft is accurate and feasible; If there is no water in goaf and inclined air shaft roadway, the resistivity tomography two-dimensional measurement results are generally high resistance abnormal closed circle, if there is water, it is low resistance abnormal closed circle< 2. Transient electromagnetic method (TEM) is to observe the inced secondary field which changes with time caused by the eddy current inced by the underground geological body ring the intermittent period of sending a pulse magnetic field to the underground. The size of the secondary field is related to the electrical property of the underground geological body. The attenuation speed of the inced secondary field of the low resistance geological body is slow and the voltage of the secondary field is large; The inced secondary field of high resistivity geological body decays faster and the secondary field voltage is smaller. According to the characteristics of the attenuation curve of the secondary field, we can judge the electrical property, nature, scale and occurrence of the underground geological body. Because the signal received by the transient electromagnetic instrument is the electromotive force of the secondary eddy current field, after normalizing the secondary potential, according to the change of the normalized secondary potential value, we can indirectly solve the geological problems such as collapse column, goaf and fault. This method has the advantages of high resolution, high efficiency, little influence by terrain, and can penetrate the high resistivity overburden, and has rapidly developed into an efficient and fast geophysical method. The transient electromagnetic method is applied to the detection of a goaf, and the effect is good. It not only infers the scope of the underground goaf, but also judges the water accumulation in the goaf
3. Very low frequency electromagnetic method
very low frequency electromagnetic method generally uses the electromagnetic wave emitted by the radio with the frequency of 15-25khz as the field source. When the electromagnetic wave meets the geological body in the process of propagation, it polarizes and proces the secondary current, which causes the inced secondary field. Generally speaking, the amplitude direction and phase of the total field and the primary field after the combination of the secondary field and the primary field are not the same, which causes the distortion of the primary field. The existence of goaf can be found by measuring the distortion of some parameters with special instruments. The VLF electromagnetic method is usually divided into two methods: dip angle method and wave impedance method. When detecting high resistance body, the wave impedance method is generally used for VLF electromagnetic method measurement. The direction of the measuring line should be consistent with the direction of the transmitting station or the angle between the measuring line and the direction should be minimum
4. Ground penetrating radar (GPR)
GPR uses high-frequency electromagnetic wave to send it from the ground to the ground through antenna t in the form of wide-band short pulse, and returns to the ground after reflection by reflector, and receives it through antenna R. When propagating in the medium, the intensity and waveform of electromagnetic wave will change with the electrical properties and geometric shape of the medium. Therefore, the structure of the medium can be inferred from the two-way travel time, amplitude and waveform of the received wave. Ground penetrating radar is suitable for detecting shallow targets. Because it can replace antennas with different frequencies, it has a wide range of applications and high detection resolution, so its application in engineering has been recognized. GPR data can be processed by special software, focusing on amplitude recovery, filtering, F-K filtering and deconvolution. The time profile with high signal-to-noise ratio is obtained, which improves the identification of useful signals. The radar time profile reflects the changes of underground media more truly and comprehensively, and ensures the data quality, The electrical difference of underground medium is used to stratify and identify underground abnormal geological bodies. This method is fast and accurate, especially for the detection of underground goaf, civil air defense engineering cavern and underground karst cave< 5. MT, AMT, HMT and CSAMT methods
magnetotelluric method (MT), audio magnetotelluric method (AMT) and high frequency magnetotelluric method (HMT) are essentially passive source frequency domain electromagnetic methods for collecting natural field signals. The difference lies in the different frequency of the collected signals, the corresponding detection depth and resolution. High frequency magnetotelluric (HMT) signal frequency is high, up to 100kHz, the depth of research is shallow, from more than ten meters underground to more than 1000 meters. This depth range is just the most active depth of human mining, underground engineering construction, groundwater resources development and other proction activities. Therefore, high frequency magnetotelluric method has made great progress in both theoretical research and instrument implementation in the past ten years, and has become the main method of medium depth goaf detection. This method does not need artificial field source, has low cost, has large exploration depth, is not affected by the shielding of high resistivity layer, and has high resolution for low resistivity layer
CSAMT (controlled source audio frequency magnetotelluric method) is a method that uses a finite length wire grounded at both ends as the emission source, uses artificial source to excite the alternating electromagnetic field, observes the electromagnetic response on the surface, and calculates the wave impedance and apparent resistivity for exploration. Because of the high resolution of CSEM, CSEM can detect the geological anomaly in electrical property and become one of the methods of goaf detection. The biggest feature of this method is the use of artificial field source, which greatly increases the intensity of electromagnetic signal and makes up for the weakness of natural field source, such as weak signal and difficult observation. However, e to the existence of field source, this method also has its inherent shortcomings, such as field source additional effect, near-field effect, field source shadow effect, transition zone effect and heavy equipment, which affect the application of this method to a certain extent.
goaf is proced under the surface by man-made excavation or natural geological movement; Empty & quot;, The existence of goaf makes the safety proction of mine face great safety problems, personnel and mechanical equipment may fall into the goaf and be injured
e to the lack of timely and effective backfill and grouting treatment in some places, the area of underground goaf in China is becoming larger and larger. Goaf changes and destroys the natural balance of the earth's surface and lithosphere, resulting in Goaf Collapse and other geological disasters
the collapse of goaf is caused by the goaf of ore body (layer) and the destruction of overburden. The mechanical balance of overlying rock above the orebody will be broken when the underground orebodies of various sizes are mined and mined out. Under the action of gravity and stress, cracks and fault displacement will occur. Groundwater will take advantage of the deficiency and leak into the goaf through cracks, which will accelerate the destruction of overburden, cause the movement of strata and surface, and finally form the Goaf Collapse Area
the collapse area will not only lead to the depletion of groundwater, the destruction of cultivated land, the deterioration of ecological environment, but also damage the local houses, the ground fissure deformation of roads, the construction difficulty and cost of major projects such as expressways, railways, airports and urban buildings e to the treatment of Goaf Collapse. In addition, the surface cracks will provide sufficient oxygen for the underground natural coal seam, the underground coal fire will weaken the roof pressure of the goaf, aggravate the caving, widen and lengthen the ground cracks, and finally form a vicious circle of "ground cracks fire area surface cracks"< Gravity exploration method is to use the mass loss or surplus of underground geological bodies to observe the gravity anomaly caused by them on the surface, so as to determine the distribution, size and boundary of underground geological bodies. The quality loss of goaf e to mining results in low gravity anomaly. When the goaf is well preserved, the low value resial gravity anomaly is formed. When the goaf collapses without water filling, the mass loss value remains unchanged, but the negative density value decreases and the influence thickness increases; When the water is filled, the loss mass is compensated to a certain extent, and the negative density value is reced. No matter what kind of situation actually exists in the goaf, the local resial gravity anomaly can be detected according to the general law. Using high density and high precision microgravity survey and proper data processing and interpretation methods, the area of goaf can be controlled. In order to improve the accuracy of interpretation, the digital terrain multi-slice high-precision geological reconstruction method and three-dimensional interpretation method are adopted< In the field measurement, all the electrodes are set on a certain interval measuring line, and then connected to the programmable multi-channel electrode converter with multi-core cable, so that the electrode layout can be completed at one time. In order to collect a large amount of data accurately and quickly, the electrode arrangement, electrode distance and measuring point can be quickly converted by program control. With the help of the electrical processing software, the collected data are processed and the results are illustrated, which makes the interpretation more convenient and intuitive. Based on the results of electrical resistivity tomography in goaf and inclined air shaft of a power plant, the application of electrical resistivity tomography in goaf and inclined air shaft is discussed. The results show that the two-dimensional measurement method of electrical resistivity tomography in goaf and inclined air shaft is accurate and feasible; If there is no water in goaf and inclined air shaft roadway, the resistivity tomography two-dimensional measurement results are generally high resistance abnormal closed circle, if there is water, it is low resistance abnormal closed circle< 2. Transient electromagnetic method (TEM) is to observe the inced secondary field which changes with time caused by the eddy current inced by the underground geological body ring the intermittent period of sending a pulse magnetic field to the underground. The size of the secondary field is related to the electrical property of the underground geological body. The attenuation speed of the inced secondary field of the low resistance geological body is slow and the voltage of the secondary field is large; The inced secondary field of high resistivity geological body decays faster and the secondary field voltage is smaller. According to the characteristics of the attenuation curve of the secondary field, we can judge the electrical property, nature, scale and occurrence of the underground geological body. Because the signal received by the transient electromagnetic instrument is the electromotive force of the secondary eddy current field, after normalizing the secondary potential, according to the change of the normalized secondary potential value, we can indirectly solve the geological problems such as collapse column, goaf and fault. This method has the advantages of high resolution, high efficiency, little influence by terrain, and can penetrate the high resistivity overburden, and has rapidly developed into an efficient and fast geophysical method. The transient electromagnetic method is applied to the detection of a goaf, and the effect is good. It not only infers the scope of the underground goaf, but also judges the water accumulation in the goaf
3. Very low frequency electromagnetic method
very low frequency electromagnetic method generally uses the electromagnetic wave emitted by the radio with the frequency of 15-25khz as the field source. When the electromagnetic wave meets the geological body in the process of propagation, it polarizes and proces the secondary current, which causes the inced secondary field. Generally speaking, the amplitude direction and phase of the total field and the primary field after the combination of the secondary field and the primary field are not the same, which causes the distortion of the primary field. The existence of goaf can be found by measuring the distortion of some parameters with special instruments. The VLF electromagnetic method is usually divided into two methods: dip angle method and wave impedance method. When detecting high resistance body, the wave impedance method is generally used for VLF electromagnetic method measurement. The direction of the measuring line should be consistent with the direction of the transmitting station or the angle between the measuring line and the direction should be minimum
4. Ground penetrating radar (GPR)
GPR uses high-frequency electromagnetic wave to send it from the ground to the ground through antenna t in the form of wide-band short pulse, and returns to the ground after reflection by reflector, and receives it through antenna R. When propagating in the medium, the intensity and waveform of electromagnetic wave will change with the electrical properties and geometric shape of the medium. Therefore, the structure of the medium can be inferred from the two-way travel time, amplitude and waveform of the received wave. Ground penetrating radar is suitable for detecting shallow targets. Because it can replace antennas with different frequencies, it has a wide range of applications and high detection resolution, so its application in engineering has been recognized. GPR data can be processed by special software, focusing on amplitude recovery, filtering, F-K filtering and deconvolution. The time profile with high signal-to-noise ratio is obtained, which improves the identification of useful signals. The radar time profile reflects the changes of underground media more truly and comprehensively, and ensures the data quality, The electrical difference of underground medium is used to stratify and identify underground abnormal geological bodies. This method is fast and accurate, especially for the detection of underground goaf, civil air defense engineering cavern and underground karst cave< 5. MT, AMT, HMT and CSAMT methods
magnetotelluric method (MT), audio magnetotelluric method (AMT) and high frequency magnetotelluric method (HMT) are essentially passive source frequency domain electromagnetic methods for collecting natural field signals. The difference lies in the different frequency of the collected signals, the corresponding detection depth and resolution. High frequency magnetotelluric (HMT) signal frequency is high, up to 100kHz, the depth of research is shallow, from more than ten meters underground to more than 1000 meters. This depth range is just the most active depth of human mining, underground engineering construction, groundwater resources development and other proction activities. Therefore, high frequency magnetotelluric method has made great progress in both theoretical research and instrument implementation in the past ten years, and has become the main method of medium depth goaf detection. This method does not need artificial field source, has low cost, has large exploration depth, is not affected by the shielding of high resistivity layer, and has high resolution for low resistivity layer
CSAMT (controlled source audio frequency magnetotelluric method) is a method that uses a finite length wire grounded at both ends as the emission source, uses artificial source to excite the alternating electromagnetic field, observes the electromagnetic response on the surface, and calculates the wave impedance and apparent resistivity for exploration. Because of the high resolution of CSEM, CSEM can detect the geological anomaly in electrical property and become one of the methods of goaf detection. The biggest feature of this method is the use of artificial field source, which greatly increases the intensity of electromagnetic signal and makes up for the weakness of natural field source, such as weak signal and difficult observation. However, e to the existence of field source, this method also has its inherent shortcomings, such as field source additional effect, near-field effect, field source shadow effect, transition zone effect and heavy equipment, which affect the application of this method to a certain extent.
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