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In recent years, large-scale coal resources exploitation and utilization of a huge economic and social benefits at the same time, the over-exploitation of coal underground formation of a large number of mined-out area, coal mining area lead to a large area of ??ground subsidence, ground-level structures , transport facilities, living infrastructure, land and suffered serious damage, bring great threat to mine people's life and production are not severely affected and harm China's economic construction and social stability. Therefore, the identification of the specific circumstances of the mined-out area to avoid landslides, water inrush roof fall and other catastrophic geological phenomena occur, it becomes the current problems to be solved. Geophysical methods due to the highly efficient, non-destructive and so, in the Detection been widely used. Due to the mined-out area formed in the burial depth, spatial structure, surrounding rock conditions generally there is a big difference, so that the physical properties of different goaf reflect also showing a lot of difference, thus based on differences in physical properties as the basis for detection the suitability and effectiveness of various geophysical methods for the detection of different goaf there are some differences. At home and abroad geophysical techniques to detect more goaf detection method has some effect but there are also limitations. Such as ground penetrating radar to distinguish ability but limited depth, earthquake and Rayleigh wave layered ability, but whether to charge the water reflects the obvious, DC law subject to ground conditions and terrain affect the transient electromagnetic method is affected by the terrain, coal mining area hydrocephalus detection is better, but the resistive anomalies response is not obvious. Different gobs of physical properties, study their specific condition geophysical detection technology, supported by the necessary drilling to verify the technical approach domestic solve such problems. Departure from the basic characteristics of the coal mining area, first gobs of surface deformation characteristics, hydrology characteristics and geophysical characteristics are discussed and detailed analysis of the impact and contact between the characteristics of the coal mining area summarized; data acquisition and high-density resistivity method, field layout and data processing carried out a detailed statement, mainly including pole pitch selection, electrode layout and dead pixels rejection data stitching, terrain correction and negative forward calculation ; followed by transient electromagnetic method commonly used device briefly summarizes the device characteristics of the transient electromagnetic method, starting from the basic principles of the transient electromagnetic method, the central loop device horizontally layered homogeneous medium under the conditions of the instantaneous alternating electromagnetic response of the focused discussion on the basic characteristics of the transient electromagnetic field, transient electromagnetic method of data acquisition and processing are described, including the filtering process, the influence of terrain correction, negative forward calculation; finally with an engineering example, mainly to the high density resistivity method, transient electromagnetic method, supplemented by seismic method to detect the coal mining area, the following aspects of research: 1, high-density resistivity method better reflects the coal gobs of distribution of. Goaf cause cracks and tensile fracture of roof joints, resulting in high-density resistivity inversion chart appears resistive anomalies in scope than mining (empty area in the upper part of the mined-out area resistive anomalies); goaf water-filled, high-density resistivity inversion chart low resistivity anomalies. Overall, high-density resistivity method can better reflect the the shallow geological information, better electrical reflect the mined-out area. 2, transient electromagnetic method better reflects the distribution of state of the coal mining area. Transient electromagnetic cross-sectional view of the same the abnormal range greater than the results of the mined area, which is due to the goaf roof joints cracks and crack fissure. Prepared in order to better reflect the resistivity anomaly changes in the vertical resistivity plane contour map also better reflect the distribution of the mined-out area of ??the state. Figure 3, in the high density resistivity inversion, transient electromagnetic cross-sectional view of the upper part of the mined-out area resistive anomalies exist to varying degrees, the resistive anomalies passes gobs of presence information, to the delineation of the mined-out area plane range; in transient electromagnetic sectional view, the presence of mined-out area will cause the apparent resistivity contour abnormal fluctuations, this information can be used as the basic symbol delineated the goaf plane range. The goaf exploration more effective combination of methods complement each other with the line laid for the transient electromagnetic method and high density resistivity method, supplemented by artificial shallow earthquakes verified, incompleteness mined-out area surrounding rock, resulting in apparent resistivity anomalies greater than the mined area to transient electromagnetic, when applying geophysical data should, supplemented by high-density electrical and shallow seismic, mining depth of less than 100 meters from the coal seam thickness of less than 10 meters slowly pour the coal seam conditions empty area, the most effective geophysical methods for high-density electrical transient electromagnetic method, shallow seismic reflection method should be used as a reference.
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