Study On Gob-side Entry Retaining Technology Of Small Pillar In Deep And Thick Coal Seam

Gaojiapu Coal Mine has a large mining depth,and the main coal seam has a strong tendency of rock burst.As a high gas mine,it is necessary to adopt double roadway layout in the section,when the roadway driving distance is long and the single roadway driving is difficult to meet the requirement of air volume in the roadway driving face,but with wide pillar retaining roadway,the high abutment pressure on the pillar is easy to induce rock burst and the pillar loss is large.In addition,influenced by geological structure,mining continuity is very tense.In order to solve the above technical problems,it is necessary to adopt the layout of gob-side entry retaining with small coal pillars.A research method combining theoretical analysis,numerical simulation and on-site monitoring is adopted,aiming at the objective situation of Retaining Roadway along goaf in deep coal seam affected by multiple dynamic pressure and difficult support,the key technologies such as reasonable small pillar width,roof breaking pre-splitting blasting pressure removing method and parameters,support mode and parameters are analyzed and studied,and successfully applied in the field,by taking the gob-side entry retaining with small coal pillars in Gaojiapu 202 working face as the research background.In order to ensure the relative integrity and bearing capacity of surrounding rock of gob-side retaining roadway with small coal pillars as far as possible,it is conducive to the development of anchorage performance of bolts,and to arrange roadway in low stress area as far as possible.Through theoretical calculation and numerical simulation analysis that the low stress area of 201 working face is within 13 m of the lateral coal body of the working face.m,and then the stress distribution and surrounding rock deformation law of different pillar widths are studied by numerical simulation.The results show that when the size of coal pillar is 7m,the roadway is located in the low stress area of coal body laterally and the internal integrity of coal pillar is better and the bearing capacity is higher.Therefore,the reasonable size of coal pillar for retaining small coal pillar along goaf is 7 m.The parameters of pre-splitting blasting with broken roof are designed according to the theory of explosion mechanics,fracture mechanics and rock mechanics,and according to the actual conditions in the field.The numerical simulation of the construction scheme is carried out to verify the effect of blasting tapping,and the stress variation area and the deformation law of surrounding rock are analyzed.It reduces the influence of secondary mining disturbance on gob-side entry retaining with small coal pillars,and ensures the normal use of gob-side entry retaining during the whole service period.Based on the analysis of the drawbacks of the original support design scheme,the bolt support scheme for gob-side entry retaining with small coal pillars under the influence of repeated mining is designed by using the concept of high-strength yielding support.The deformation law of surrounding rock of roadway under different schemes is analyzed by numerical simulation.The results show that adding anchor rope support and increasing support density can effectively control the deformation of surrounding rock of roadway and maintain the stability of roadway.Mine pressure monitoring shows that after setting up 7 m small coal pillars and adopting the above scheme of roof-breaking pre-splitting blasting and roadway bolt support,the deformation of roadway surrounding rock is in a controllable range,which can meet the needs of safety production in 202 working face,and good supporting effect can be achieved.