Study On Safety Of Working Face Mining Under The Influence Of Surface Water And Goaf Water

The coal mining in the Jurassic of the Majiliang coal mine has being completion,and the Carboniferous system is currently being deepened.The 8117 working face is located in a horizontal 301^-2 panel,which is about to be mined.The coal seam is the Carboniferous 3 coal.The working face is the hills and terraces of the valley.The Majiliang ditch pass through the working face.and 2 coal,7 coal,11 coal,14 coal in the overlying Jurassic strata have been mined,forming a Jurassic goaf.Therefore,the working face is threatened by water damage from the old empty water in the Jurassic goaf and the large ditch on the surface of the horse’s spine.In order to evaluate the safety of 8117 working face mining in surface water and old air,in this paper,first study the hydraulic connection between surface water and goaf water,focus on sudy the development law of mining fissure after mining of Carboniferous 3 coal:through the field measurement method such as drilling TV and water injection test,the 1817 borehole located at 8220 working surface is observed.The variation law of mining crack in the vertical direction is counted,and it is calculated with the formula calculation,model simulation and numerical simulation.In contrast,the upper limit of the development height of the water-conducting fracture zone is finally determined,and the crack-production ratio of coal seam mining is determined.Finally,the safety of the 8117 face mining was evaluated based on the observations at the 8220 working face,and a high-limit mining plan and electrical monitoring program was designed for the 8117 face to prevent roof water damage.The specific workload and research results obtained are as follows:（1）There are a large number of Jurassic coal seam goafs on the top surface of the8117 working face,and the surface of the horse’s spine and its branch trenches pass through.Through analysis,it is determined that the 2 coal old airspace is directly replenished by the surface of the Majilianggou River,and the 11 coal and 14 coal goafs are not directly replenished by surface water.（2）The 1817 hole was drilled and TV observation,and the crack and separation development of the buried depth of 310-400m were counted.The main conclusions are as follows:1)The total fracture area is smaller at the depth of 310-330m,and becomes larger from the depth of 330m,and increases sharply at the depth of 380-400m.2)The abscission layer is more developed in the 310-350m section of the buried depth than the 350-400m section of the buried depth.The water flowing fractured zone determined by drilling TV is developed to a height of 150 m.（3）A water injection test was carried out in the 310-400 m section of the 1817 hole depth,and the changes in water permeability and permeability coefficient were observed.The permeability coefficient increases from 340m deep,and the permeability coefficient increases again at a depth of 380m.According to the results of the water injection test,the development height of The water flowing fractured zone determined is 140m.（4）According to the recent 2014-7 hole data from the 1817 hole,the lithology of the roof overburden was analyzed.Different roof lithology types were used,and the different formulas provided by the regulations were used.The development height of The water flowing fractured zone determined was between 51.42 and 84.58m.The height of the water-conducting fracture zone simulated by the model is 150m,and the numerical simulation of the water flowing fractured zone is 120m.（5）The results of drilling TV,water injection test,formula calculation,model simulation and numerical simulation are compared.Finally,the results of on-site measurement are taken,that is,the development height of the water flowing fractured zone is 150m,and the crack-production ratio is 24.27 times.（6）According to the observation results,the safety of the 8117 working face during mining was evaluated,and most of the working face did not meet the requirements of the specification.In order to safely mine the working face,a height limit scheme was designed for the 8117 working face,and the inter-hole electrical method is designed to further monitor the water flowing fractured zone.