| China is one of the most serious countries affected by coal and gas outburstdisasters in the world，one of the disasters occurred in the Carboniferous-Permian coalseams. Coal and gas outburst area is the stacking area of the tectonic coal developmentarea and gas-rich region. Studies have shown that the electrical parameters(mainlyrefers to the resistivity and dielectric constant)of geological structure zone and thestress concentration clusters will change significantly, which led to significant changesin the spatial distribution law of electromagnetic field. Therefore, for the study ofelectrical variation of the coal is significance for proving tectonic coal developmentareas and gas-rich region and predicting occurrence of coal and gas outburst.Based on the National Natural Science Fund Project-The Study on theCharacteristics of being loaded low-frequency electrical parameter of gas-containingcoal and rock (50,904,024), the paper establish the experimental system of lowfrequency electrical test parameters about coal containing gas, select different typescoal samples of representative coal mine as study samples and testing the characteristicdifferences and variation of the electrical parameters of different metamorphic gradecoal and different type of structure coal of does not contain gas, in the process ofadsorpting gas by coal and deformation and fracture under load process about the coalcontaining gas; based on the mining of rock mechanics and ground electrical theory，based on other research achievements. At the same time, experimental testing of theindustrial composition analysis, pore structure, macerals of the studied samples.Combined with the theory of coal petrology, physics of dielectrics, gas (CBM) geology,analyzes the mechanism of influence in the press of deformation and fracture underload about the coal containing gas by gas, stress, construction composition of the coaland rock, the microscopic structure of the coal and rock, the test frequency and so on.Trough test studying and theory analyzing, some conclusions are obtained.(1)Dielectric constant is larger in raw coal than that in briquettes under differentloads. With the gas content increasing in coal samples, electrical resistivity becomesdecreasing while dielectric constant increasing. When gas adsorption reaches to themaximum, dielectric constant becomes stable. (2)Dielectric constant and electrical resistivity are continuing changing followingabove mentioned regularity with loads increasing under triaxial compression condition.But, electrical resistivity of Hebi meagr-lean coal isn’t following the regularity. Intriaxial compression process, electrical resistivity in raw coal and is smaller thanbriquettes, while dielectric constant is larger than briquettes. electrical resistivity ofanthracite is smaller than meagr-lean coal, while dielectric constant is larger.(3)Frequence and electrical resistivity are in negative correlation.The gaspressure and electrical resistivity are also in negative correlation, while in positivecorrelation with dielectric constant. For different adsorption capacities of differentcomposition in coal, the affection degrees to dielectric constant are also different.，being CO2>CH4>N2.(4)All mine coal samples with the increase of soaking time, the resistivitygradually decreases, the dielectric constant increases gradually；Coal mineral in thebody have different effects on electrical parameter level, effect of kaolinite onelectrical parameter to be much more than to quartz, calcite and other minerals on theinfluence of electrical parameters of coal; the pore and larger cracks of the coal,impact on electrical parameter of coal, dense structure of raw coal, crack less,compared with briquette, less resistivity, larger dielectric constant. |
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