Study On Mine Pressure And Its Control Technology Of Fully Mechanized Working Face With Top Coal Caving And Weak Floor In Dafosi Mine

The high mining stress and the weak instability of the floor in the fully mechanized top coal caving stope with weak floor lead to the frequent occurrence of surrounding rock failure such as rib spalling and floor heave in the working face.At present,there are many thick coal seam(11.4m)fully mechanized top coal caving face under the condition of weak floor(aluminum mudstone)mining in Binchang mining area.This type of stope space is often affected by surrounding rock failure accident.Therefore,based on laboratory test,theoretical analysis,numerical calculation and industrial test,this paper analyzes the failure types and occurrence mechanism of surrounding rock problems in 40119 coal face of Dafosi Coal Mine in Binchang mining area,studies the surrounding rock control effect of retaining different bottom coal thickness and adopting soft bottom fully mechanized caving face with different setting load strength.The research results further enrich the mine pressure and rock layer control theory and technical means of soft bottom fully mechanized top coal caving face,mainly in the following aspects:(1)Mechanism of rib spalling in 40119 working face.On the basis of Griffith theory and Mohr—Coulomb theory,the failure mechanism of thick coal bed is studied,and it is revealed that a large number of unit coal bodies have tensile fracture instability and shear slip failure instability.The theoretically calculated failure depth of 40119 coal face under Lade-Duncan yield criterion is 2.3m.(2)Floor heave mechanism of 40119 working face.On the basis of slip line field theory,the failure law of floor heave of fully mechanized caving stope with weak floor thick coal seam is analyzed,and the high stress of roof to weak floor leads to slip deformation of floor along weak surface of structure.According to the motion characteristics of bottom rock mass,the theoretical failure depth of floor is 7.2m.(3)The bottom coal thickness control effect on the strata behavior.Analysis of the control mechanism of coal wall and floor on working surface.By means of numerical simulation method,the failure characteristics of surrounding rock in working face space are analyzed when different thickness bottom coal is left,and it is found that when weak floor thick seam fully mechanized caving stope enters bottom coal mining from bottomless coal mining,the failure of stope surrounding rock is greatly reduced,and the control effect of bottom coal on surrounding rock is very significant.When the thickness of bottom coal thickness is more than 0.6m,the control range of bottom coal damage to stope surrounding rock is gradually slowed down.(4)The control effect of setting load on strata behavior.The control mechanism of coal wall and floor is analyzed by increasing the setting load of the working face.The numerical simulation results show that the setting load increment is negatively correlated with the floor heave,that is,when the setting load increases,the floor heave decreases gradually,and when the setting load changes from 7000 k N to8000 k N,The setting load increment has the best control effect on the surrounding rock.(5)Analysis of strata behavior results in test section of 40119 working face.It is found that the failure of surrounding rock affected by floor heave and high mining stress can be effectively controlled by setting bottom coal and increasing setting load in fully mechanized caving stope with soft bottom thick coal seam.The existence of bottom coal and the increase of setting load can make the support better play its supporting ability in the "support-rock" system,reduce the shrinkage of the support when the working face comes to press,and reduce the influence of roof movement on coal wall and floor,so as to realize effective control of stope surrounding rock.The paper has 80 pictures,15 tables and 74 references.