Abstract: In the early stage of a mine in Shandong,room-and-pillar mining was mostly used,leaving a large number of high-quality resources. It will not only cause disasters such as air leakage in the goaf,spontaneous combustion of the seam,instability of the pillar,but also destroy the integrity of the seam,which brings great difficulties to the recovery of pillar resources. Based on the above problems,the coal slurry-based cementing material was proposed to pre-fill the pillar goaf,and the performance test of the coal slurry-based cementing backfilling material was carried out. The flow and mechanical properties of the slurry under the action of additives such as water reducing agent and strengthening agent were tested and analyzed. Considering the creep effect,the effect of increasing the strength of the backfilling and strengthening pillar was quantitatively analyzed. The results show that the water reducing agent C is the main control factor of the slurry expansion degree,the strengthening agent D is the second largest influencing factor of the early strength of the specimen,the cement proportion B is the main influencing factor of the later strength of the specimen,and the mass concentration A is the main common factor of the slurry performance. The lateral constraint provided by the filling body significantly improves the bearing capacity of the pillar,and the creep compressive strength of the pillar increases linearly with the increase of unilateral filling thickness. The results of this study have certain reference significance for the pre-filling room-type empty area of coal slime-based cementing materials and the recovery of underground sluggish mineral resources. 

Key words: coal slime,orthogonal test,creep,filling reinforcement