| Coal and gas outburst is one of the complex dynamic disasters and also the difficult subject worldwide in this area. Generally, serious outburst disasters not only cause huge economic losses, but also engender possibly great casualties. Over recent years, the disasters of coal and gas outburst occur more frequently, especially after the coal mines are being gradually transferred to deep mines, the phenomenon of high geo-stress, gas pressure and permeability become increasingly apparent, has become a major disaster mainly from outburst of industrial safety field in China, bringing more technical difficulties on the early-warning and control of coal and gas outburst. In this paper, taking some typical strong outburst face of sixth level in Xinzhuangzi coal mine, in Huainan as the research object, A new idea and new method for hazard mechanism and early-warning of coal and gas outburst is proposed, furthermore, the essence mechanism and micro-fracture precursor law for induced outburst are mainly discussed with the use of the theoretical analysis, numerical simulation, mathematical statistics theory, non-linear fractional theory and industrial field tests, In addition, the evaluation indexes and early-warning model of coal and gas outburst hazard in extracting coal face are emphatically elaborated, and the evolution features and gas-rich region determining method of overlying rock mining crack are systematically studied by means of microseismic monitoring technology, consequently some significant research results have been obtained.Based on the gas-solid coupling model of coal-rock with gas failure process, on one hand, the multi-field coupling evolution law for stress field, fracture field and seepage field is analyzed and improved; on the other hand, the evolution features for background stress field and its activity information for micro-fracture precursor of outburst process are simulated reconstruction by using of RFPA2D-GasFlow.The process of initial cracks occurring and extending for coal-rock sample under vertical loading is simulated in terms of RFPA2D, the microseismic effect and its evolution law of coal-rock failure process is revealed deeply, and the microseismic phenomenon is further verified. The results show that the microseismic effect has its special advantage to study evolution law of micro-cracks, mechanical mechanism and local deformation features for coal-rock mass, and based on this feature, the failure process of coal-rock is real-time and dynamic monitored, finally, which provides technical basis for prediction and forecast of gas outburst disasters. In order to meet the needs of microseismic monitoring system for coal mine underground, part of system software-hardware equipments, installation devices and its installation method are developed, improved or redesigned. Taking the artificial burst test to calibrate velocity model method, the optimization of velocity selection for monitoring area and its effects on the source location accuracy are studied, and the layout principle for sensors also put forward. A set of comprehensive analysis method for multi-parameters identifying and filtering out noise is established based on the long and short average method (STA/LTA) detecting principle for complicated signals.Taking time effect evaluation into account, the evaluation index of outburst hazard length is established; on account of the normal distribution theory, a 2 a warning model is established to describe outburst hazard, the feasibility of which is verified by manual blasting inducing coal and gas outburst. The mechanical mechanism and criterion of slip instability is investigated, and then the mechanical model of fault structure is derived, based on the above, the relationship between fault zone activity law and outburst is derived. Combined with case analysis, the outburst hazard evaluate process of the tunneling and roadways with faults with the 2 a warning model is further studied, and then whose warning results are checked in various ways, which proved the reliability of 2 a model.With the basic overburden rock failure theory, a mining overburden mechanical model, which believes that tensile and shear stress areas are respectively formed within overburden zone, is established, the tensile stress mainly distributes within break line of caving zone, and the shear one within the vertical fracture zone. A detailed analysis by numerical simulation is carried out for the initial fracture germination, propagation until macroscopic extension, the acoustic emission property and the energy dynamic evolution of overburden. With the fractal geometry theory, a quantitative description of overburden failure process is reduced ordered and dissipative. Based on the mechanism of mining pressure relieved gas with roadway retained drilling, we believed that there is an irregular and close vertical fracture field which is a "cylindrical lying mass" within the fracture zone. According to the distribution law of the field, low order drilling on the roof is optimized. |
PDF Full Text Request