Preliminary analysis of roof water hazard risk based on"two-zones"exploration technology:An example of Bofang coal mine
In this paper,a variety of"two-zones"exploration techniques,such as drilling fluid leakage obser-vation,core recovery rate statistics,drilling hole television observation and drilling hole resistivity dynamic monitoring,are used to study the development characteristics of water conducting fracture zone in the overly-ing rock of No.3 coal seam in Bofang coal mine,and the risk of roof water disaster under the influence of No.3 coal seam is analyzed.The research result shows that the development height of water conducting frac-ture zone in 3213 working face is 87.66m,and it develops to K9 sandstone aquifer.The development height of the caving zone is 22.61m,which develops to K8 sandstone aquifer at the lower part of No.2coal seam.The maximum height of the caving zone in 3313 working face is 20-21m from the roof of coal seam to the sandstone aquifer in the roof of No.2 coal seam.The maximum height of the water conducting fracture zone is 83-87m from the coal seam roof to K9 sandstone aquifer.The calculated caving/mining thickness ratio is 3.58-3.76,and the fracture/mining thickness ratio is 14.85-15.56.The water conducting fissures produced by the mining of No.3 coal seam can cause the connection between the sandstone aquifers of the Lower Shi-hezi Formation and Shanxi Formation of Permian system and the goaf of No.3 coal seam,and the groundwa-ter in the aquifers percolates downward through the water conducting fissures,increasing the risk of roof wa-ter damage.It is suggested that the mine strictly implements the relevant requirements of roof water disaster prevention and controlling treatment,and reduces the impact of mining fissures on the normal production of the mine.
water-conducting fracture zonedynamic monitoring of drilling hole resistivityoverlying rock failureroof water hazard
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