Study Of Experiment Of Gas-filled Coal Mechanical Properties And Mechanism Of Delay Outburst Coal And Gas

In general case, coal and gas delay outbursts account for a small proportion of total outburst accidents. But they are very harmful because their occurrences are delayed and invisible, the workers are possibly working and have no time to prevent them. A series of experiments were carried out by ASAP 2020 V3.01 H Surface Area and Porosity Analyzer, HCA High Pressure Volumetric Method Adsorption System, AGI-250kN SHIMADZU, MTS815 Rock Mechanics Test System, self-made"Gassy Coal THM Coupling System"and"the large-scale test device for coal and gas outburst simulation"in this dissertation. The field experiment studying the relationship of ground pressure, gas pressure and value of drilling cuttings weight is carried out at 2124 fully mechanized coal mining face of Sanhui mine in Tianfu Mining Company. Based on the analysis of all experiment results, we can obtain the mechanism of coal and gas delay outburst according to the energy criterion, mechanics criterion, failure criterion of local disturbance and space-time mechanism of unstable failure on coal and rock of distressed zone at mining and tunneling face. The main research results are as follows:1. The delay outburst coal samples have strong adsorption capacity as same as the outburst coal samples and mechanical strength as same as of non-outburst coal samples. It may be one of the important reasons inducing coal and gas delay outburst.2. The damage constitutive equations of vertival stress-strain of coal samples are respectively established under the conditions of uniaxial compression and triaxial compression based on the mechanical experiment. The confining pressure and elastic modulus of coal samples exist in logarithmic function relationship. The damage variable and axial strain of measured values after the yield point of coal samples exist it too.3. We have modified Darcy Law formula considering the influence that deformation exerts on the permeability of coal samples under the triaxial compression. Comparing with the condition that neglecting the deformation's effect, the maximum deviation is more than 20%. Therefore, we should consider it.4. The relationship equations of effective stress and permeability are established and the seepage properties of coal samples are obtained by the gas seepage experiment of coal samples under the triaxial compression. The effective volumetric stress and permeability of the delay outburst coal samples exist in negative exponent relationship.5. The change direction of permeability rate and damage variable is same by the gas seepage experiment of delay outburst coal samples under cyclic loading. The change of the permeability rate and damage variable is very obvious at the first few cycles, but tends to be stable after several cycles. It shows that the permeability rate is related to the damage degree.6. The positive relationship of ground pressure, gas pressure and value of drilling cuttings weight drilling cuttings weigh and ground pressure, gas pressure is derived by the field experiment based on 2124 fully mechanized coal mining face of Sanhui mine in Tianfu Mining Company.7. The results of the simulation experiment show that coal and gas delay outburst is the result of both ground stress and gas pressure interaction. The prepare process of outburst can describe to the balance of original rock stress broken by mining work, ground stress distributing again, the coal and rock fracture development, adsorption gas in coal seam desorbing to free gas, gas pressure increasing, the hard coal and rock of plugging weak lamination broken by gas pressure and ground stress and outburst happened by gas swelling power. The critical gas pressure influences the outburst intensity which reflects damage degree at delay outburst. The energy of transportation outburst coal power is provided mainly by gas expansion energy.8. Based on above-mentioned studies, We redefine the conception of coal and gas delay outburst. We can obtain the mechanism of coal and gas delay outburst according to the energy criterion, mechanics criterion, failure criterion of local disturbance and space-time mechanism of unstable failure on coal and rock of distressed zone at mining and tunneling face.