Feasibility Study On The Hydrogeology Of The Lower Coal Group Mining In East Wing Area Of No.5Mine Of Fengfeng Coalfield

Carboniferous-permian coal seams are widely distributed and their resources areabundant in coal fields of North China.In recent years, the demand for energy has been onthe increase and the intensity of mining has also been on the rise, which leads to theshrinking of the shallow coal reserves (upper coal group).In order to prolong the usage ofcoal mine, it is imminent to mine the lower coal group while Ordovician limestone is themain aquifer affecting the mining of lower coal group. With the increase of mining depth,the water pressure of Ordovician limestone on seam floor becomes bigger and bigger. Thethreat of Ordovician limestone to the mining of lower coal group gets more and moreserious.In order to achieve the safety and high efficiency of the lower coal group mining, itis very significant to make a feasibility study on the hydrogeology of the lower coal groupmining.Owned by Fengfeng Group, No.5Mine is mining upper coal group (Damei,Yizou,Yeqing and Shanqing). With annual capacity of300,000tons, its actual recoverablereserve is only50million tons left by the end of2010.Coal in upper part that has beenmined for52years has dried up.Threatened by Daqing Limestone and Ordovicianlimestone, the lower coal group has not been mined. So the mining of lower coal group isimminent.Combined with the hydrogeology conditions of No.5Mine, this paper carries out thefollowing work:(1) With27borehole data of No.5Mine as basic data, the3-d geological model of eastwing area is generated by the use of GMS software. Then, by analyzing the east-west andsouth-north sections, it is found that the depth of coal seam from the south to the northincreases gradually.(2)According to27borehole data of No.5Mine, the water-irruption of XiaoqingDaqing and Xiajia coal is predicted with the method of water bursting coefficient. Theresult of prediction is the following: the water bursting coefficient of this area is larger thanthe empirical value-0.06Mpa/m. If we mine the lower coal group without preventivemeasures, there will be the threat of water bursting.(3) At last, the present study proposes water preventive measures for the lower coalgroup mining: two measures of “drainage and decreasing pressure” and “reconstruction ofcoal seam floor” to Daqing aquifer adopted; the “reconstruction of coal seam floor” measure adopted to Ordovician limestone aquifer. And the paper also puts forward thewater preventive measure of the joint of Daqing and Ordovician limestone, injectingOrdovician limestone first, and then injecting Daqing.