Strata Behavior Of The Mixed Mining Working Face Of Fully Mechanized Gangue Backfilling Mining And Caving Mining In Pingdingshan No.12 Coal Mine

This paper takes the mixed mining working face of gangue backfilling mining and caving mining in Pingdingshan No.12 coal mine as the engineering background.Based on its production system layout,the key equipment selection of the working face,and the backfilling mining technique,this paper studied the strata behavior of the mixed mining working face of gangue backfilling mining and caving mining through physical simulation and numerical simulation,the main achievements are as follows:(1)Based on the physical simulation experiment,the strata behaviors in the caving section,gangue backfilling section and the transition section have been revealed.The strata in the caving section shows caving belt,fissures belt and bending subsidence belt.The gangue backfilling section mainly shows the fissure belt and bending subsidence belt,while the caving section is not obvious and height of the caving section increases as the ratio of gangue backfilling section length and caving section length decreases.Also the roof movement will be more obvious as the ratio decreases.(2)It shows that how the advancing distance of the mixed mining working face and the gangue backfilling section length influence the vertical stress.The stress in the layers over the caving section is obviously smaller than that in the gangue backfilling section.And the stress is mainly concentrate on the boundary of the gob and the transition part of the working face.The stress will increase as the working face advances and the gangue backfilling section decreases.(3)It discusses how the advancing distance of the mixed mining working face and the length of the gangue backfilling section influence the sinking form and the length of the transition section.The following results are obtained.In the gob,the strata behavior in caving section is more obvious than the gangue backfilling section and the sinking shape is like the spoon.And different from the traditional working face,the maximum subsidence point is offset to the middle points of the mixed mining working face.With the advancing distance increasing,the position of the maximum subsidence show in a line and the maximum value is increasing with length of the gangue backfilling section.For the length of the transition section in the mixed mining working face,it increases as mixed mining face advances and increases while the gangue backfilling section decreases and finally tends to be stable.The transition section length varies in the range of 6.2m~13.5m,if the hydraulic support is 1.5m in width,it will be within the range of 4~9 supports.(4)According to the engineering practice of the Ji15-31010 mixed mining working face of the Mixed Mining of Fully Mechanized Gangue Backfilling Mining and Caving Mining in PingdingshanNo.12 coal mine and the characteristics of the transition section,this paper gives the number of the hydraulic supports in the transition section based on the methane concentration and supports strengths.Then the resistances and distributions of the hydraulic supports in caving section,gangue backfilling section and transition are analyzed to determine the first weighting and periodic weighting distances in three sections above.Finally,how the bearing force in coal body of the gangue backfilling section and the caving section vary with the advancing distance is stated,which proves the vertical stress characteristics in gangue backfilling section and caving section.