| In recent years,large-scale exploitation and utilization of coal resources,has brought huge economic and social benefits,however, over-exploitation of coal has led to the formation of a large number of underground gob area.Coal gob area led to a large area of surface subsidence, ground buildings,transport facilities, life infrastructure, soil suffered serious damage, it also bring great threat to the people's living and production in mining area and cause serious implications and hazards to China's economic construction and social stability. Therefore, avoiding the occurrence of geological phenomena, such as collapse, water invasion, roof caving and other disasters, has become a pressing problem.Geophysical methods are widely used in the detection Of gob area because of the characteristics of efficient, non-destructive and so on. However, due to the general big differences in Ages, burial depth, spatial structure and surrounding conditions of gob area, there are big difference in physical properties reflection of different mined areas. In consequence, various geophysical methods which are based on the differences in physical properties may have different suitability and effectiveness in detecting in different gob areas.While at home and abroad, there are many geophysical techniques in detecting gob area, each method has some effect but there are also limitations. For institute, GPR has strong resolution but limited in depth,the seismic and Rayleigh wave has strong layered ability, but reflect not obviously to whether water filling, direct current prospecting can be greatly influenced by grounding condition and topographic relief, the transient electromagnetic method is little influenced by topography and has better Mined-out area of coal mine water detection effect, but for high resistance abnormal reaction is not obvious. The characteristics of physical property according to different mined-out area for its specific conditions, the effective geophysical detection technology, combining with the necessary drilling verification is the the main technical way to solve the problems in present.This article from the basic characteristics of coal goaf on mined-out area, first of all discussed and analyzed the surface deformation characteristics, hydrological features and geophysical characteristics in detail, and summarized the characteristics of coal goaf between contact and influence, then made detailed elaboration to the high density resistivity method of data collection and data processing, field quasi-geoid, content mainly includes polar distances selection, electrode layout, bad point eliminate, data matching, terrain correction and are inversion, etc. Then simply described the common device of the transient electromagnetic method is, summarized the transient electromagnetic method characteristics of each device. Then gived the key discussion to transient electromagnetic method, which is based on the basic principle of horizontal layer under the condition of uneven medium to line device of center of transient electromagnetic response. And the basic characteristics of the transient electric magnetic field, the transient electromagnetic method of data collection and processing is expounded,mainly include filtering processing, topographic influence and calibration, are inversion calculation; high density resistivity method and transient electromagnetic method is given priority to, seismic reflection wave method for coal goaf complementary. We have made the following several aspects of the research results:1.The high-density resistivity method well reflect the distribution state of coal goaf. Due to the roof goaf joints and fractures and ripping caused cracks, resulting in high density resistivity inversion chart, appear high resistance anomaly area is goaf range(Upper appear high resistance abnormal in mined-out area);When water filling in goaf, after the high-density resistivity inversion figure appear on the low resistance abnormalities. Overall, the high density resistivity method can better reflect shallow geological information of mined-out area, good electrical reflection.2.Transient electromagnetic method also well reflect the distribution state of coal goaf. In the transient electromagnetic section, as well as coverage than abnormal results of mined-out area range, which is due to the roof of mined-out area caused by joints and fractures and ripping fracture. In order to better reflect the anomalous the vertical change, we compiled the resistivity plane equivalence value maps, also well reflect the distribution state of mined-out area.3.In high-density resistivity inversion figure, transient electromagnetic section, in the upper part of mined-out area exist to varying degrees high resistance abnormalities, the high impedance abnormal goaf existing information passed, and draws the goaf plane range. More effective method of mined-out area exploration combination of transient electromagnetic method heightening density resistivity method quasi-geoid with line, with mutual complement of artificial shallow earthquake verified. Due to the surrounding rock goaf imperfection that lead to abnormal resistivity coverage than goaf range, when quoted should geophysical data with transient electromagnetic primarily, high-density electrical method and shallow earthquake is complementary, less than 100 meters in depth, thickness of coal seam of less than 10 meters under the condition of sloping inhibition coal goaf, the most effective geophysical exploration methods for high-density electrical method and transient electromagnetic method, shallow seismic reflection wave method should be used as a reference. |
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