Experimental study on concentrated stress transfer characteristics of district coal pillars in contiguous coal seams
The research on the characteristics of stress transfer from coal pillars to floor is directive to determine the control method of roadway surrounding rock in contiguous coal seams.Based on the contiguous seam in Duerping coal mine in Shanxi province,the similar model test of upper seam excavation is carried out,and the horizontal strain data of different floor depths were collected by using DIC technology,the distribution characteristics of vertical,horizontal and shear strains and the variation law of the horizontal distance between the peak strain and the boundary of coal pillar are analyzed,which explores the concentrated stress transmission to floor from sectional pillars in upper seams after mining.The results show that:in the floor area of the coal pillar,the three strains are distributed asymmetrically in twin peaks with the center of the coal pillar as the axis,the peak values of vertical and shear strains on the first excavation face is smaller than that on the later excavation face,the horizontal strain peak value is just the opposite,the three strain peak values decrease as the floor depth increases.The vertical and shear strains of the goaf floor tend to 0 far from the coal pillar boundary,however,the horizontal strain showed the character of repeated increase and decrease.The horizontal distance among the three strain peaks and the boundary of the coal pillar shows that the vertical strain is larger on the side of the coal pillar by the first excavation face than on the side of the coal pillar by the later excavation face,but the shear strain is just the opposite,and the horizontal strains of successive faces are equal on the side of the coal pillars,the horizontal distance between the three strains and the boundary of coal pillar increases with the increase of floor depth.The vertical and horizontal stresses are compressive and tensile stresses respectively,while the shear stresses at the side of coal pillar in successive mining faces is tensile and compressive stresses respectively,the vertical and shear stress are both high stress level,but the horizontal stress is very small,the peak values of vertical and horizontal stress are located in the floor area of coal pillar,while the peak values of shear stress occurs in the floor area of goaf,the vertical and shear stresses tend to 0 with the distance increase from the boundary of coal pillar,and the horizontal stress shows the character of repeated transformation.The selection of wall rock control of contiguous seams roadway should concern vertical stress,and shear stress on instability and failure.
contiguous coal seamsdistrict coal pillarstress transfer characteristicssimilar material model testDIC technology
NETL
NSTL
万方数据
