Research On Deformation Characteristics And Support Technology Of Floor Roadway Affected By Goaf In Liangbei Coal Mine

When the goaf is formed in the coal seam face of underground coal mine,the deformation and damage of the floor rock stratum of the stope occur in a large range.At this time,the stability of the surrounding rock is affected by goaf when the roadway is arranged in the close rock stratum of the floor under the goaf.When the reserved coal pillar is used between the working faces especially,the stresses of the adjacent goaf and the coal pillar overlap with each other,the deformation characteristics of the surrounding rock of the roadway are very complex,and the support difficulty increases.Based on the engineering background of-550 m horizontal opening roadway arranged in Liangbei Mine under goaf,this paper uses RMT-150 B rock mechanics experimental system to test and analyze the mechanical parameters of roadway surrounding rock,and calculates the failure range of mined-out floor based on limit equilibrium theory.FLAC3 D numerical simulation software was used to analyze the failure characteristics and stress distribution law of floor strata and roadway under goaf.Combined with the field investigation,the segmentation control technology of floor roadway influenced by goaf was proposed.The main conclusions are as follows:(1)The maximum failure depth of floor in 11151 goaf is not more than 13.6 m.Although the roadway in the failure mode of floor in goaf is in the area of stress reduction,the roof structure of roadway has been damaged in a large range,cracks have developed,and there is a large difference in lithological strength,showing asymmetrical distribution characteristics.(2)After the goaf completely collapsed,the central floor strata gradually recovered to the stress level of the original rock,and the concentrated stress formed at the coal walls on both sides reached 3.1 times of the original rock stress,presenting a "double peak" distribution,and the stress distribution of the floor strata decreased with the increase of vertical depth.(3)The stress distribution of floor strata is affected by the superimposed stress of adjacent goaf and coal pillar,and the influence is severe within the range of 80 m from coal pillar to floor strata of goaf.When floor roadway is arranged in this area,the disturbance characteristics are obvious.There is a linear relationship between the width of coal pillar and the stress distribution of floor rock.With the increase of the width of coal pillar,the concentrated stress of floor rock and the plastic zone of roadway surrounding rock decrease obviously.The larger the width of coal pillar is,the less influence it has on the floor rock and roadway under goaf.(4)With the increase of the vertical distance between the roadway and the goaf,the stress of the roadway decreases obviously.The control technology of dividing the floor roadway into three sections of 10 ～ 15 m,15 ～ 20 m and more than 20 m.Based on the collaborative control theory of internal and external bearing structures,the combined support technical parameters of "high-strength anchor mesh cable + deep and shallow grouting + re-spraying" are given,and the segmented differential control technology of long and short anchor cables and reinforced anchor cables are applied in different sections.(5)The field application results show that the deformation of roadway basically tends to be stable after two months,and the maximum subsidence of roof is 35 mm.The proposed support technology ensures the long-term stability of floor roadway,and the control technology provides a good reference value for the same type of roadway.There are 78 figures,8 tables and 101 references.