Research On The Mechanism Of Delay Outburst Of Coal And Gas

Coal containing gas bursting is a complicated dynamic phenomenon where massive mixture of gas and coal erupt abruptly from the inner coal wall to the excavation area. China is one of the countries where the coal containing gas bursting happens the most around the world. The delay coal containing gas bursting accounts for only a small portion. However, its elusiveness and hysteresis make it abrupt and unpredictable, which might happen when people are working on excavation so as to cause massive casualties, delay coal containing gas eruption has much to do with the rheological character of coal containing gas and the presence of the distressed zone before mining face. Therefore, the study of rheological constitutive model and failure criterion of gas coal with rheological character and the effect of outburst mechanism of coal and gas extension based on distressed zone has significant importance to the revelation of mechanism of delay coal containing gas bursting and to the prevention strategies.The paper applies respectively Burgers Body, Generalized Kelvin, and Poyting-Thomson Body to investigate the triaxial creep when the stress level is below the yield stress and then conducts a comparative analysis of the results. The comparison demonstrates that Burgers Body is the best model to represent the viscoelasticity and the rheological property of coal containing gas. By connecting this model in series with a nonlinear viscoplastic body, a new nonlinear viscoelasto-plastic theological model of coal containing gas is built. Then, the paper conducts a fitting analysis of the triaxial creep data of coal containing gas when the stress level is above the yield stress so as to test and verify the accuracy of the model. Subsequently, the paper applies the new model to deduct a time formula which can calculate the delayed time of the exposed coal containing gas bursting, so that measures can be prepared to effectively prevent the occurrence of casualties caused by coal containing gas eruption.In addition based on outburst mechanism of extraction face distressed zone extension for coal and gas, prevention and control measures were researched and put forward. Considering ground and gas stress as a function of time and supposing its redistribution time were continuous, a function of situ stress and gas pressure were created as M (t), and then by coal and gas outburst determine the conditions obtained extension of the prominent area of coal and gas-based relief. Since coal and gas delay prominent mainly affected by the impact of coal and rock creep and distressed zone, the total time of the extension of coal was the sum of the time of gas coal creep buckling and distressed zone of instability.