Study On The Characteristic Luling Coal Mine 10th Coal Seam Overlying Strata And Desruction During The Process Of Stoping

The excavation of coal causes the deformation and destruction of overlying strata and creats fractures which offer channels of gas.The concentration of gas accumulate to some extent,as can induce an affect on the safety of coal mining work.How to avoid the destruction of gas is the most important part of coal mine safety production.According to the sphere of action,the measures of preventing of gas can be divided into regional and local measures.Excavtion of protecting strata is the most efficient and economic regional method compared to the other measures.The excavation of protecting strata can relieve the stress inside the proected strata and make it gas permeable,so that the adsorbed gas accumulated in the coal seam will be released and the pressure of gas can be reducted considerably,as can prevent gas outburst.As we all know from the "Three Area" Theory that during the exavation,there are caving zong,freatured zone and bentand susidised zone in the strata.The gas circulating channel mainly distribute in the freatured zone,where the gas exhaust laneway are usually installed to intercept the gas from the upper coal seam and the goaf of the mined bed.So the combination of protecting strata and gas exhaust laneway will be more effective in contracting the gas desorbed from the coal seam.Luling coal mine located about 20 kilometers away in the southeast of Suzhou in Anhui.Its output is up to 2,300,000 tons and it is identified as high-risk gas outbust coal mine,expecially in its 8th coal seam.The 10th coal seam which is about 50m away below the 8th coal seam is specified as the protecting strata.However, the spread of the 10th coal seam whose thcikness, the lithological character and petrofacies of its roof and the distance between 8th coal seam and it is variable is untable.The characteristics discussed above all affect the deformation and desruction of 10th coal seam and the permeablilty and the degree of pressure relief of protected strata.Moreover,the deformation and destruction characteristic of excavated strata is the foundation of identifying the installing parameters of upper gas drainage laneway and upper corner gas drainage hole.So the study on the deformation and destruction characteristic of overlying strata during the excavation of the 10th coal seam is very important to coal mine safe and efficient production.This paper considered sedimental environment of the studying area and the occurance condition of 10th coal seam,started with studying geologic structures and the characteristics of rock and combination of the overlying and underlying strata of 10th coal seam,divided the overlying strata of 10th coal seam into some engineering geologic zones through the fuzzy comprehensive envaluation method,took the excavating parameters and geologic structure as boundary conditions to analysis the desruction discipline and pattern,characteristic of pressure of overlying strata,regularity for change of coal wall support pressuer,deformation characteristics of strata horizontal movement and vertical subsidence through RFPA on the base of the determination of mechanic datas from drill cores,which comes from studied strata,finally predicted the deformation and destruction of relevant pattern of underlying strata in different zones.Finally, this paper divided the researching area into four parts in horizontal plane according the characteristic of the deformation of underlying strata and predict that the height of fracture zone developed in the underlying strata of different districts is between 20-60m.