Study On The Movement Of Surrounding Rocks And Sectional Coal Pillar Width Setting During Shallow Seam Mining

In this paper,the method of combining field investigation,theoretical analysis,numerical simulation experiment,similar material simulation test and field monitoring of mine pressure is carried out on the background of pillar setting in the section of fully mechanized mining face of 2-2 upper coal seam in Yang Jia cun Coal Mine,Inner Mongolia.In this paper,the evolution of lateral support pressure and pillar setting in shallow coal seam under fully mechanized mining conditions are studied and verified in engineering practice.The main research results are as follows:(1)The coal seam of Yang Jia cun Coal Mine is stable,without gas and water inrush danger;Through the rock core and the indoor rock mechanics test,it is found that the strength of the coal and the rock is relatively low and the strength of the roof rock is relatively high.The obtained rock mechanics parameters provide the basis for the following tests.(2)The formation structure of Yang Jia cun coal mine is analyzed,the stability of "Vous-soir Beam" structure in coal seam mining is calculated,and the bending,abscission layer,fracture and collapse process of roof motion of coal seam mining are obtained by similar material simulation.The evolution trend of the stress of the key stratum in coal seam mining is monitored,and the position of the fracture line of the key stratum is obtained,and the influence of the stress perturbation on the fracture and instability of the key stratum and the overlying strata is analyzed.In order to simulate the effect of fault activation or mine earthquake phenomenon on goaf during coal seam mining,applying horizontal stress to the model,it is observed that the model produces an upward development fracture,and the fracture is produced,extended and transfixion with the increase of horizontal stress.The upward development of interpenetrating fractures can affect the surface of the earth.(3)The stress distribution in different stages of seam mining is simulated by numerical simulation.According to the law of stress evolution curve,the lateral stress evolution of coal under dynamic load action is divided into four stages,and the plastic zone of coal in each stage presents a general increasing trend.Under rheological condition,the stress concentration of lateral support decreases with time,the limit equilibrium zone increases gradually,and the influence range of lateral support pressure becomes smaller and smaller.The time when the overlying rock movement tends to be stable and the region with high elastic energy stress concentration in goaf are obtained.(4)According to the limit equilibrium theory,the plastic zone width of the seam mining is 5.3m,the stable minimum theoretical width is 9m,and four different width sections of coal pillar retention schemes of 9m,12m,15m and 20m are obtained;FLAC3D is used to simulate the stability of coal pillar in four different width sections of 9m,12m,15m,20m.It is concluded that the 15m pillar is beneficial to maintain the stability of roadway and to provide the recovery rate of resources,which can be used as the reasonable width of coal pillar in the section;The range of plastic zone of coal pillar and the width of elastic zone and the deformation data of surrounding rock of roadway under mining conditions are obtained by field monitoring,which provides reference experience for coal seam mining and similar mine mining in the future.