Study On The Evolution Mechanism Of Coal And Gas Outburst And Outburst Elimination Engineering Application

Coal and gas outburst,one of the most devastating and complex mining dynamic disasters in underground mining,is currently a worldwide problem.It will not only bring huge economic losses,but also cause some casualties.As one of the countries with the most serious coal and gas outburst in the world,China has a large amount of outburst mines with wide range,high frequency and intense outburst,which causes the difficulties in outburst prevention and management.At present,in research on coal and gas outburst mechanism,divergences and difficulties remain.The mechanism has not been thoroughly made clear.The prevention and controlling of coal and gas outburst is still a major technical problem faced by the coal mine production.Therefore,clarifying the main mechanism of coal and gas outburst and ensuring the safety of coal mine production are the key issues of high-yielding and efficient production of outburst mines.With the development of society and economy,there is an ever-growing demand for energy.At the same time,the exploitation and utilization of gas is more and more noticeable and important.Therefore,research and management of coal and gas outburst have important social value and economic significance.Through the simulation of the inoculation,initiation and propagation processes of coal and gas outburst,the spatial-temporal evolution laws of coal containing gas during coal and gas outburst are analyzed from the angle of its induction mechanism.Through the research on its evolution mechanism,the coal and gas outbursts'developing process is revealed;some methods and ideas of the prevention are proposed as well.The results provide some useful methods and ideas for the research of coal and gas outburst and its prevention.The main research content are as follows:?1?“Simulation experiment system of coal and gas outburst under three dimensional stress”has been developed independently,making use of the inversion of the system of coal containing gas under the fully closed position by three dimensional stress and pore pressure the role of active breeds of coal and gas outburst,the whole process of the occurrence and development of physical simulation experiments;The tightness and reliability of each system and the stability of each monitoring system are realized under the condition of one way maximum load pressure 30MPa.Three dimensional axial pressure and lateral pressure of gas bearing coal are realized.?2?Through studies on the evolution mechanism and strength of outburst by a self-developed“Simulation experiment system of coal and gas outburst under three dimensional stress”,the research results proposed that coal and gas outburst is a complicated process.Affected by the human mining activities,the coal under comprehensive stress occurs deformation and failure with the fractures increase and connected.The original adsorbed gas desorb and turn into the free state.Then the original balance of gas adsorption in coal is broken,and the gas begin to migrate to the lower gas pressure direction through the fractured channel.When the gas accumulated in coal can not be released at normal speed,coal and gas outburst occurs due to the comprehensive action.The research shows that the effect of coal and gas outburst is not only affected by stress and gas pressure,but also closely relate to the physical and mechanical properties of coal,especially characteristics of coal in the outburst place with free weak surface.Put forward the judgment criterion of coal and gas outburst;the relation between was intensity of coal and gas outburst and ground stress and gas pressure discussed in this paper.It found that the thrown coal accumulate the most in outburst place after the coal and gas outburst,and then gradually reduced and vanished in the farther place.Most of the coal and gas outburst occurred in the moment of the strongest outburst.?3?Based on acoustic emission evolution regularity of coal and gas outburst and the study of acoustic emission signal characteristics,four stages of the initial compression,elastic deformation,plastic deformation and destruction were discussed.The acoustic emission events firstly occurred in the weak structure surface far from the central position of the coal.As the three-dimensional stress increased,the number of acoustic emission events increased significantly.At the same time,the number of acoustic emission events increased from a slow speed to a faster speed,then increase rapidly,and eventually become slow as the completion of outburst.Through the study on the law of development of deformation and failure of coal,a structural model was put forward,that is,the deformation and failure of the coal containing gas was similar to the ellipsoid in the process of coal and gas outburst.This provided a theoretical basis for the study on coal and gas outburst and the controlling of outburst.?4?Based on theory of the computer numerical simulation and mathematical model of the solid-gas coupling,the numerical simulation of the coal and gas outburst process was preformed using the numerical simulation software of RFPA^2D-GasFlow.The results showed that the coal deformed and broken as well as the free gas flowed due to the increase of strain.With the comprehensive effects of tensile and compressive stress from the in-situ stress and gas pressure,the destruction zone with approximate ellipsoid was formed in front of working surface,and the coal and gas outburst was deduced,and maintained until reaching the new equilibrium state.Based on the simulation of the functions of the three factors?gas pressure,in-situ stress and physical and mechanical properties of coal?of the coal and gas outburst,the conclusion can be proposed,that is,the gas pressure supplies the power source for the coal and gas burst,speeding up the destruction of coal containing gas and the broken coal expulsion;the stress plays a leading and decisive role in the process of coal and gas outburst;the coal strength plays an important role in hindering of coal and gas outburst.?5?Through the analysis of the criterion of coal and gas outburst and the test of the industrial test on the field of hydraulic slotting.It turned out that the hydraulic cutting seam outburst prevention technology had a eliminating or reducing effect on the three elements influencing coal and gas outburst in various degree.It not only reduced the effect of stress on coal,but also increased the resistance strength and reduced the internal pressure of coal.To some extent,it eliminated the danger of coal and gas outburst and prevented coal and gas outburst effectively.