Space-time Evolution Of Mining Pressure Field In Gently Inclined Medium-thickness Seam And Overburden Rupture Rule

In 21 TH century,with the rapid development of China economy and technology,the development and using of coal resources is becoming more and more important in national economy.Where formation stress and safety mining during mining arise people’s concerns.In the procession of colliery exploitation,along with the tunnel drilling and face mining,stress field of surrounding rock will be redistributed.The change of stress in infection zones of coal mining,especially the redistribution of stress of rock mass will impact on the integrity and stability of the surrounding rock of roadway,even result in instability and destruction of surrounding rock,arise coal crushing in high stress area and coal and gas outburst,affect the production of coal directly.Therefore,the monitoring,control and research of mining pressure field gradually are becoming one of the problems as important as coal mining,getting the attention of people.Based on actual situation of Baijiao mine,studied the space-time evolution regularities of surrounding rock pressure field in mining gateway in gently inclined coal seams,and the broken variation of overburden.It has provided technological and theoretical basis support for safe and efficient mining of working face.Simulated variation of surrounding rock pressure with different distance in mining gently inclined medium-thickness seam,in-depth study evolution laws of overburden ruptured and the space-time evolution regularities of mining pressure field based on finite difference software’s Flac3 D in this paper.Here are some preliminary conclusions:①Theoretically analysis coal and rock mass stress,caving form and the extension of destroy crack in mining gently inclined medium-thickness seam;system discussed the divide of "Three Zones" in overburden failure and confirmed it’s scope of influence;analysed mechanical model of overburden strata destruction and described the space form of fracture field based on the results of previous studies.②Process the rock sample into standard specimen in lab.The general compressive strength of samples proved as 39.13 MPa by rock mechanical properties tests;calculate the cohesion of c by Mohr stress circle theory and rock rupture angle θ; where the general cohesion of c of three groups specimens is 7.95 MPa.In combination with mechanical property test and engineering geological conditions obtained the physical and mechanical properties of coal measure strata;supporting material parameters for numerical simulation.③ Used finite difference software Flac3 D simulated gently inclined medium-thickness seam mining.Results show that:the stress field influenced by mining and the max vertical stress of surrounding rock nearby uphill pillar is 50.33 MPa when the working face promoted 50 m,while the stress increased to 66.58 MPa when promoted 150 m,it has increased 48.34 MPa than initial stress which was 18.24 MPa before mining.At the same time,the max roof sinkage is 20.30 cm where the field measurement is 24.80 cm.The simulation results agree well with field measurement level.④The comparison between model calculated results and field monitoring data of surrounding rock stress showed that: the status of monitoring points influenced by stress change more and more significantly with the working face advanced,vertical stress increased gradually even the rate of change gradually deepens with working face comes near.Also the changes of roof displacement is effected by mining stronger and stronger.