Study on separated layer water burst mechanism for weakly cemented giant thick glutenite

There is a giant thick glutenite aquifer with weak water-bearing intensity on the main coal seam in Anxin Coal Field. However, water inrush disasters occurred in several working faces during mining. Finding out the water inrush mechanism is the basis of mine water disaster control. Based on the analysis of hydrogeological characteristics, the zoning characteristics of the thickness and water-rich intensity of the glutenite aquifer were elucidated. By means of uniaxial compressive strength, triaxial acoustic emission and X-ray diffraction, the physical and mechanical properties of the roof aquiclude were obtained. Based on theoretical analysis of key layers, the relationship of fracture zone and mining catchment zone, and similar simulation tests, four hydrogeological structure model of water inrush for the glutenite aquifer were established and water inrush mechanisms for the glutenite aquifer were revealed. At last, the engineering criteria and prevention measures for water proof protective layer instability were put forward. The research results showed that the aquifer in the eastern part of the study area is moderately water-rich, and many water inrush occurred in the weak water-rich area in the past. The clay mineral content in the roof mudstone reached 59.6% with a strong hydrophilicity and good water-resisting property. The strength of the roof aquiclude decreased after mining, and it was easily become good water-conducting channel under the action of upper rock load and hydrostatic pressure of mining catchment zone. The glutenite aquifer had special physical and mechanical properties, and pore-fissures developed and changed to be water-bearing abnormal zone after mining disturbance. The water inrush intensity of giant thick glutenite was related to the characteristics of the lower bedrock, the height of the water-conducting fissure zone and the thickness of the water-proof protective layer. The engineering criterion of water burst for weakly cemented glutenite is the protective layer less than 30 m in the normal area and less than 60m in the geological structure area respectively. Study on the separated layer water burst mechanism and engineering criterion for weakly cemented giant thick glutenite can provide reference for the water inrush prevention in the western coal fields.