| After the thick and extra thick coal seams are mined out,the roadway adjacent to the goaf has large deformation in a certain space-time range behind the mining face,even large deformation occurs continuously for a long time,which seriously affects the safety extraction of the coal mine.With the increase of coal seam mining height,this phenomenon is becoming more and more serious.The existing research results on the stress distribution,temporal and spatial change law of abutment pressure and its influence on the dynamic pressure roadway surrounding rock stability cannot clearly explain the lateral abutment pressure temporal and spatial change law and the dynamic pressure roadway surrounding rock stability,because of the increase of mining height and the thick hard roof strata thickness,mechanical properties and vertical position.In addition,there is a lack of functional expression to describe the temporal and spatial change law of lateral abutment pressure.In view of this,using theoretical analysis and numerical simulation methods,the influence of mining height,roof rock structure and the thick hard roof strata movement on the temporal and spatial change of lateral abutment pressure are systematically studied.And then the dynamic pressure roadway surrounding rock stability affected by the lateral abutment pressure temporal and spatial change is analyzed.The research results will provide a theoretical basis for the determination of coal pillar width,tunnel and support time,support method and strength of dynamic pressure roadway along the goaf which affected by full height fully mechanized mining / fully mechanized top coal caving in thick and extra thick coal seams.The main work and achievements are as follows:(1)Aiming at the influence of mining height and roof rock structure on lateral abutment pressure distribution.Based on the thick and extra thick coal seams roof rock structure and mining technical conditions,the coal seam roof structure composed of coal seam,interlayer,thick hard strata and loose layer is generalized.Combined with the Kerr elastic foundation assumption and time growth function,the prediction model of lateral abutment pressure distribution is established.And then the effects of mining height and roof rock structure on the characteristic indexes of lateral abutment pressure distribution(lateral abutment pressure peak value,coal wall failure zone width,limit equilibrium zone width and abutment pressure distribution range)are studied.The results show that the coal seam depth,mining height,the height(vertical position)of thick hard stratum in roof from coal seam have a significant impact on the characteristic indexes of lateral abutment pressure distribution.With the increase of coal seam depth,the lateral abutment pressure peak value increases linearly,and the coal wall failure zone width,the limit equilibrium zone width and the abutment pressure distribution range increase logarithmically.With the increase of mining height,the lateral abutment pressure peak value decreases exponentially,and the coal wall failure zone width,the limit equilibrium zone width and the abutment pressure distribution range increase linearly.With the increase of the vertical position of thick and hard stratum,the lateral abutment pressure peak value and the limit equilibrium zone width decrease exponentially,and the abutment pressure distribution range increases linearly.The influence mechanism of mining height and the thick hard roof stratum on the characteristic index value of lateral abutment pressure distribution is that the change of lateral abutment pressure is caused by the change of vertical in-situ stress and mining additional stress in the coal seam,and the change of mining additional stress distribution is caused by the change of mining height and the thick hard roof stratum.(2)Aiming at the time effect of the thick hard roof stratum movement on the lateral abutment pressure distribution.The change process of lateral abutment pressure distribution with time under the conditions of thick hard roof stratum are studied by numerical simulation.The functional relationship describing the change of the lateral abutment pressure peak value with time is given.The influence of mining height and thick hard roof stratum characteristics on the stability time of lateral abutment pressure is studied.The results show that the characteristic indexes of lateral abutment pressure distribution gradually increase and stable with time,and the stability time of the peak value is greatly affected by the thick hard stratum movement.The time change curve of the lateral abutment pressure peak value is expressed by negative exponential function,which can be used to calculate the stability time of lateral abutment pressure after coal seam mining.The stability time of the lateral abutment pressure peak value is significantly affected by mining height and the vertical position of the thick hard stratum.With the increase of the mining height and the vertical position of the thick hard stratum,the stability time of the lateral abutment pressure peak value increases logarithmically.The main reason is that with the increase of mining height and the vertical position of the thick hard stratum,the elastic foundation coefficient of the interlayer decreases,the force of the thick hard stratum on the interlayer decreases,which increases the stability time of the deformation of interlayer and the lateral abutment pressure peak value.(3)Aiming at the space effect of the thick hard stratum movement on the lateral abutment pressure distribution.The spatial change process of lateral abutment pressure distribution under the condition of thick hard roof stratum during the working face advancing are studied by numerical simulation.The functional relationship between the lateral abutment pressure peak value and the working face advancing distance is given.The influence of the mining height and thick hard roof stratum characteristics on the lateral abutment pressure lag distance of mining face is studied.The results show that with the working face advancing,the characteristic index values of lateral abutment pressure gradually increase until it is stable.The lateral abutment pressure peak value lag distance of the working face is greatly affected by the thick hard stratum movement.The spatial change curve of the lateral abutment pressure peak value is expressed by negative exponential function,which can be used to calculate the distance behind the working face when the lateral abutment pressure peak value is stable after coal seam mining.When the lateral abutment pressure peak value is stable,the stable distance behind the working face is significantly affected by mining height and the thick hard roof stratum.With the increase of mining height and the vertical position of the thick hard stratum,the lag distance increases logarithmically.(4)Aiming at the influence of time-space change of lateral abutment pressure on the surrounding rock stability of dynamic pressure roadway along the goaf.The coupling calculation of continuous discontinuous method is adopted.The load calculated by the negative exponential function expression of the spatial evolution of the lateral abutment pressure peak value is taken as the stress boundary condition at the top of the numerical model.The effects of the lateral abutment pressure peak value and its stability distance,coal pillar width and tunneling time on the deformation of roadway surrounding rock are studied.Based on the influence of time-space change of lateral abutment pressure on the surrounding rock stability of dynamic pressure roadway along the goaf,a method to determine the coal pillar width and tunneling time of dynamic pressure roadway is given.The results show that the lateral abutment pressure peak value,coal pillar width and roadway tunneling time have significant effects on the surrounding rock stability of the dynamic pressure roadway.With the increase of the lateral abutment pressure peak value,the roadway surrounding rock maximum deformation increases exponentially.With the increase of coal pillar width,the roadway surrounding rock maximum deformation first increases logarithmically,then decreases exponentially.With the lag of tunneling time,the roadway surrounding rock maximum deformation decreases exponentially.Under the action of lateral abutment pressure,the main reason is that the lateral abutment pressure change leads to the increase of stress and its increase time of roadway surrounding rock,which enhances the plastic expansion of coal and rock mass at the end of bolt anchorage.The reasonable coal pillar width and roadway excavation time are determined according to the relationship between the deformation of roadway surrounding rock and them,and combined with the negative exponential function expression of time-space change of peak lateral abutment pressure.An optimized design scheme for tunneling the headentry along the goaf in the 3405 working face of Shanxi Lanhua Kechuang Daiyang coal mine,which is 70 d or 221 m behind the top coal caving face with a17 m coal pillar reverse tunneling. |
PDF Full Text Request