Optimization study on filling material beside gob-side entry retaining

In order to make gob-side filling body of gob-side entry retaining adapt to the roof movement, the properties of concrete material is modified by adding polymer and steel fiber to achieve the purpose of “yield-support”. The test of modified concrete was carried out to test the uniaxial compressive strength under different ratios, and the best ratio of each component was determined. The stress of filling body and displacement of upper and lower plate are simulated by FLAC3D numerical simulation method to analyze yielding performance. The results show that the ethylene vinyl acetate copolymer（ＥＶＡ） improves the plastic deformation ability of the concrete material, and steel fiber has a good effect on the ductility of concrete. When the dosage of polymer is 15%, the yielding property is 6.10%. The results of numerical simulation show that the modified concrete of gob-side filling material can sink with roof and release the pressure of the roof movement under the condition of its own strength, and finally achieve the purpose of coordination and yield. In addition, the best width of filling body beside gob-side retaining entry is 1.2 m.