Control technology of flexible bow-shield-supporting system for gob-side entry retaining in highly inclined seam

Steeply dipping coal seam accounts for 15%～20% of China’s total coal reserves.In western China,more than 50% of coal mines belong to steeply dipping coal seam.In order to realize gob-side entry retaining in steeply dipping coal seam,it is necessary to develop new gob-side entry retaining technology.Based on the ‘τ’ structure model of strata movement in large inclined coal seam mining,the bow flexible shield support was invented and successfully applied to the No.31321 large inclined coal face of Shidonggou Coal Mine.The gob-side entry retaining was realized,the coal loss was reduced and the recovery rate was improved.The results show that the developed bow-shaped flexible shield support system has the function of hardness and softness,that is,the single support has large stiffness and can withstand high pressure.Under the thrust of gangue in the caving zone,the support system can move horizontally and has flexible function.Through the field test,it is found that the bow flexible shield support retains the roadway along the goaf,giving full play to the support and shield effect of the support.The support bears less roof pressure and does not bend downwards or break.The combined structure formed by the support and the compacted caving zone can effectively control the mine pressure and during the normal period and the weighting peried,the safety factor of the support is 2.724 and 1.363 respectively,and the support can be recycled and reused.The research results put forward a new method for non-pillar mining in steeply dipping coal seam.