Prediction Analysis of Overburden Rock Failure Height and Size Determination of Sand Control Coal (Rock) Pillar in Working Face Mining

Aiming at the sand control and water prevention problems of the 33_lower06 working face in Gaozhuang Coal Industry, which was located in the Quaternary thick loose layer - thin bedrock condition, the "two zones" prediction formula of overburden rock and the actual measured data of the 3_lower301 working face were comprehensively adopted to analyze the development heights of the overburden rock collapse zone and water conducting fissure zone in the 3_lower coal under the condition of mining height of 3.0-4.6 m. The results indicate that the water richness of aquifers in the lower section of the Quaternary Lower Group was weak, and the water isolation property of the bedrock weathering zone was good, which basically doesn’t pose a water (sand) threat to the working face; The collapse zone heights under different mining heights were about 16.69-43.61 m, and the heights of water conducting fissure zone were about 41.4-59.8 m. After taking into account the 20 m depth bedrock weathered aquifer zone, the minimum height of the sand control coal (rock) pillar was 46-78 m. The working face mining height should be determined by zoning according to the mining range of the 3_upper coal seam and the local bedrock thickness. In sections where the bedrock thickness doesn’t meet the corresponding coal (rock) pillar retention requirements, the mining height should be reduced or protective coal bodies should be retained. This comprehensively considering the close distance coal seam repeated mining, the overburden rock failure height, and the depth of the weathered aquifer zone of the bedrock, can provide reference for the sand control coal (rock) pillar retention and mining height determination under similar thick loose layer - thin bedrock conditions.