Risk Assessment of Water and Sands Burst of Coal Seam Mining with Thick Loose Layer and Thin Bedrock

According analysis of hydrologic and geological data and drilling results of 43 downward 20 working face，then the characters of aquifer and aquifuge of the Quaternary loose layers，thickness and water resistant of clay at the bottom and overlying thin bedrock structures were revealed，and mining numerical simulation model of thick loose layers and thin bed rock working face was built，collapse zone height was 14m，water flowing fractured zone height was 33m，the type of working face mining safety coal and rock pillar was ‘roof sands resistant safety coal and rock pillar’，the height of sands resistant coal and rock pillar was 24.3m after calculated.The results showed that water flow fractured zone and coal and rock pillar height by theory all smaller than the thin bedrock thickness 33m，water and sands burst risk was nonexistence when working face mining height was 2.5m.