Experimental Study On Simulation Of Coal And Gas Outburst Under Different Load Level

Being one of the serious natural disasters threatening the safety production of coal mine at home and abroad, coal and gas outburst is a kind of extremely complex dynamic phenomena of geology which happens during the process of coal mining. With the increasing of mining depth, the ground stress and gas pressure is enlarging, besides, the geological and technical conditions of coal mining is growing more complex, thus the frequent gas dynamical disasters (e.g. gas explosion and coal and gas outburst), which bring great threats to the safety production of coal mine. Natural factors are what greatly influence the coal and gas outburst, and gas dynamic disasters are mainly attributed to parameters like geological structure, ground stress, rock mass structure of coal, gas pressure and gas content, and coal mining activities.On the basis of hypothesis of the synthetic effects of coal and gas outburst, the present study analyzes the mechanical properties of coal sample by using the TSZ-2.0 automatic tri-axial apparatus produced by NanJing Soil Instrument Factory Co., Ltd, and carries out simulation experiments of coal and gas outburst under three distinct loads with a design of different vertical stresses, horizontal stresses and step loads by utilizing the large-scale test device for coal and gas outburst simulation independently developed by the Key Laboratory for Exploitation of Southwestern Resources and Environmental Disaster Control Engineering (Chongqing University).After the brief introduction of the structure of and concrete operation procedures for the large-scale test device for coal and gas outburst simulation independently developed by Chongqing University, the thesis describes the fabrication of shaped coal sample for experiment, the division of collection areas of coal sample after outburst, and the experimental program. Specifically speaking, there are simulation experiments of coal and gas outburst under uniform load of different vertical stresses and horizontal stresses and of coal and gas outburst under non-uniform step load which have been done in the present study, the results of which show that the different levels of stress on have certain effects on coal and gas outburst. In the experiment under uniform load, when the stress of one direction is constant, with the increasing of the stress of another direction, the mass of outburst coal sample is becoming larger and the mass ratio of outburst coal sample in the total amount of coal loading is bigger, i.e. the absolute and relative intensity of outburst is increasing with the enlargement of stress level. In the experiment under step load, the absolute and relative intensity of outburst is also increasing with the developing of the stress level of the stress concentration region; in addition, after rubbing down the outburst hole model using gypsum, it's found that most of the outburst hole models are typical and the greater the experimental load is, the larger the solid measure of the outburst hole and the mass of gypsum mold are.Moreover, comparing the smooth and steady temperature signal which is realized through wavelet de-noising of temperature evolution curve, the results indicate that the greater the stress level is, the temperature increment of coal sample during the adsorption and charge process is smaller, the slower the increasing of coal sample temperature is, and the longer the time that gas pressure grows from 0 MPa to 1 MPa during charge process is. The outburst temperature of coal sample is decreasing at the instant of outburst and then slower.