采矿工程毕业设计

The method of mining in ChinaThe Known coal-bearing area is about 0.55 million km2 in China. Almost all the provices, cities, autonomous regions (including Taiwan Provice) possess certain amount of coal reserves. China is one of thc countries in the world of which the coal reserves are richest. The proved reserves accounted for 782234Mt at the end of 1985.The main deposition characteristics of coal formation in China are as follows:(1) The geologic period when the coal was formed is long. From early Palaeozoic Era to the Quaternary Period coal deposition was already proved. So various types of deposting states and multiseam formation were found.(2) The geological structures suffered by coal-bearing formations are much more, So various geological conditions are encountered in coal depositing fields, such as folds, faults, irregular thickness and inclination of coal seams. As considering the thickness of coal seams, the amount of reserves of thin coal seams accounts for 17.36%, of mediun thick coai seams for 37.84%, of thick coal seams for 44.8%; As considering the inclination of coal seams, the amount of reserves of gently inclined coal seams accounts for 85.95%, of inclined oal seams for 10.16%, of inclined seams for 3.89%. It be seen that 0f gently. inclined medium thick and thick coal seams account for most part of the total reserves.All of the above factors determined that the mining methods practically adopted must be! manifold. According of incomplete statistic information there are totally 54 of mining methods which have been experienced in China. The formation of these mining methods has undergone a long period. Especially, after thefounding of P. R. China mining methods are gradually devoloping, reforming and improving, and abundant experiences have been accumulated.China is not only one of the countries in the world which produce large amount of coal each year, but also one of the earliest counhries in the world which exploit and utilize coal reserves.The history of exploiting and utilizing coal reserves in China began as early as 6 to 7 thousands years ago.Before liberation, only the machines powered by steam engine were used in few productional link, such as in hoisting, water drainage, ventilation etc. Some quite backward mining methods, like the entry retreating mining and abandoned pillar mining etc, were employed, and the extraction and developing operations were mainly completed by hard handwork. The working conditions of miners and the safety conditions of coal mines ware extremely poor, there were no any measures to prevent mine hazards, and fatality accidents were severe.After the founding of the P. R. China, the old mining methods were gradually reformed. In May of 1950, the resolution of "Conducting the Reform of Production Methods and safe production" was issued by the Ministry of Fuel Industry, it requires that Production reform would be carried out step by step. Firstly, the out of date mining methods would be changed into new longwall-type methods in order to raise coal recovery rate. This resolution insisted the production must obey the principle of "safety first". Therefore, the ventilation conditions of mining sections and mines as well as the working environment must be improved. Latterly, the first "Safety Regulations of Underground Coal Mines" (a draft), the "Resolution about the Safety Works of Coal Mines" and the "Resolution about Carrying out New Mining Methods in All theCoal Mines" were issued, and it was emphasized that the reform of mining methods is a revolution in coal mining industry. After that, reform of mining methods was Carried out all over the country.In gently inclined thin and medium thick coal seams, the old entry retreating and abandoned pillar mining method were changed into longwall mining; In thick coal seams, high-face stoping caving method was changed into the downward inclined slicing with top-coal retained or under the protection of false timber roof, the downward horizontally slicing caving method with false top-coal or timber roof, and a few changed into ascending hydraulic filling method. Meanwhile, roof grading was carried out according to the experiences at hme and abroad in order to benefit selecting different roof control methods for different roof conditions.During this period, great achievement was obtained in the reform of old mining methods. Up to 1957, the output produced by means of longwall mining in the state operated coal mines accounted for 92.6%, the coal recovery rate of mining sections raised to about 70%, and the working environment and conditions of safe production were apparently improved.The roof control in longwall face eliminates the situation of no supports as in old mining methods, the support types changed gradually from timber props and framed timbers to metal frictional props plus hinged bars.in gently inclined and inclined thick or extrathick coal seams, the top-slicing caving mining under the protection ofartificial false roof was tested and improved. The oringinal false timber roof was changed into bamboo curfain, waaved twigs of the chaste tree, and mainly into metal-mesh false roof. Moreover, clay grouting was used for forming regenerated roof. In gently inclined extrathick coal seams, ascending inclined slicing longwall mining on the strike associated With hydraulic filling was also practised.For steeply inclined thin and medium thick coal seams, inverted bench mining by means of compressed air hammer was tested at the beginning, then tongwall mining was adopted. In steeply inclined thick coal seams, the horizontally slicing and slant slicing were practised firstly, and the method of mining under the protection of flexible shields was latter tested successfully and spreaded. Besides, the strip shrinkage stoping to the rise, the oblique longwall-type shrinkage stoping on the strike and the sublevel blasting mining method were also practised. The combined mining method with the help of metal shield mesh was tested too in extrathick steeply inclined coal seams.Many experiences have been accumulated in the process of adopting longwall mining. For example, the clay grouting used in inclined slicing longwall caving mining on the strike for extracting thick and extrathick coal seams can not only prevent spontaneous combustion of coal, but also be advendtageous to forming regenerated roof, thus improve roof conditions and enhance the application scope of downward caving mining method. Another example is changing the double-entry system into single-entry system, thus the developing-extracting ratio decreased.At the mean time, developing mechanized mining to ease the hard labour works was paid much attention by the government. The MLQ-64 type shallow-web single drum shearer, which was made out in Xiaohengshan Coal Mine (Jixi CMA), combined with SGW-44 type chain scraper conveyor, metal frictional props and hinged bars equipped the first ordinary mechanized working face in 1964, which realized the mechanization of coal extraction, loading and conveying operations. Such an ordinary mechanized mining method spreaded rapidly, andthe degree of mining mechanization raised from 4.11% at the end of "1st 5-Year plan" to 15.3% at the end of "3rd 5-Year Plan", which made the longwall mining be consolidated and developed.In order to further improve the longwall mining, researches on fully mechanized mining were carried out. The first set of fully mechanized mining equipment, which was designed and made domestically, was tested underground in 1974. Meanwhile, complete sets of fully mech anized mining equipment were imported from abroad.In 1978, fully mechanized mining entered a new developing period in China after the Third Meeting of Eleventh central Commitee of the Chinese Communist Party. In September of 1979, the first "Technical Policies of Coal Industry" was issued by the Ministry of Coal Industry, it stipulated that fully mechanized mining is the developing direction of coal industry.With reforming and opening, more than 100 sets of fully mechanized mining equipment were imported and wide-ranging international exchanges were in progress, which speeded the researches of home-made fully mechanized mining equipment and made these equipment reach the abroad advanced level in some aspects. Now the fully mechanized mining equipment suitable to gently inclined thin and medium thick coal seams as well as inclined slices of thick coal seams can be designed and made at home.To suit the development of coal industry, the new "Technical Policies of Coal Industry" was revised and issued in 1987, which further indicated that the development of fully mechanized mining must be speeded.The developing history of fully mechanized mining is introduced in Table 1-1.Latter, the newly manufactured MLQ2-80 type, DY-100 type and DY-150 type single drum shearer, MLS3p-170 type double-drum shearer replaced the MLQ-64 type, MLQ2-80 type single drum shearer, the new SGW-150 type chain scraper conveyor replaced the SGW-80 type conveyor, the individual hyeraulic props replaced the metal frictional props. Above mentioned 3 kinds of new face equipment formed the second generation of ordinary mechanized mining, which was tested firstly in Feicheng CMA and achieved good technio-economic results. After that, the new MG-150W1type double-drum shearer associated with SGZCF630 / 220 type chain scraper coveyor and long metal Fl type bars formed the third generation of ordinary mechanized mining, which achieved much better technico-eco- nomic results.At the same period, the blasting mining technology of longwall faces developed quickly.several new techniques, such as the blasting with millisecond delay detonator, the blasting-proof type individual hydraulic props the double-speed large, power chain scraper conveyor and the technology of loading coal with the help of blasting et., have been successfully tested and spreaded gradually in suitable conditions.Moreover, the hydraulic supports used for the fully mechanized mining with top-coal drawing and the corresponding mining technology have been studied and tested since 1982. The first set of equipment for fully mechanized mining with top-coal drawing was tested in the gently inclined extrathick coal seam of Puhe Coal Mine (Shenyang CMA) in June of 1984. In April of 198'6 this mining method tested again in the steeply inclined extrathick coal seam of No.2 Coal Mine (Yiaojie CMA) and achieved good results. Soon afterwards, this mining method applicated in several other coal mines and also achieved successes, its indices of output, efficiency, safety and others are better than that of the traditional mining methods, like the horizontally slicing, the slant slicing, flexible shields, oblique roadway retreating mining and so on.The method of fully mechanized mining with top-coal drawing was also tested in thegently inclined thick and extrathick coal seams in Pingdingshan CMA, Yangquan CMA, Luan CMA etc. some of them achieved good results. But some problems have not been resolved yet, such as the spontaneous combustion of coal, the accumutation of dust and methane, the unstable coal recovery rate etc.The method of top-coal drawing mining with the help of sliding-bar type supports was tested in some steeply inclined and gently inclined extrathick coal seams. For example, in Huating Coal Mine (Ganshu Province), Baizhigou Coal Mine (Bing County of Shanxi Provice) and Xinyao Coal Mine (Chongxin County of Ganshu Province) the technico-eco-nomic indices of this mining technology are apparently better than that of the old mining methods. However, some problems still exist, they are mainly that the stability of the sliding-bar type supports is not good in case of the coal seam possessing big inclination angle.It has been clearly regulated in the "Technical Policies of Coal Industry" that fully mech- anized mining is the developing direction in our country. After undergoing researches, tests and application, a series of fully mechanized mining equipment suitable to extracting gently inclined working faces with medium mining height have been formed preliminarily, which have had the capacity of satisfying the domestic needs. The developing directions of fully mechanized mining in next step are:actively raising the operating ratio of the equipment and the working-time utilization rate; increasing the monthly face production and economic profit;improving the current equipment, increasing its capacity and reliability;focusing efforts on developing the fully mechanized mining equipment used for difficult conditions, such as the "weak-3', "hard-3' (here the number 3 means the roof, the coal seam and the floor), big inclination angle; large mining height etc;It is considered that the fully mechanized mining technique used in simple gently inclined medium thick coal seams or the thick coal seams mined by slicing has been ripe. Generally speaking, this technique has been reached or approached to the internation level of early 80’s, and has achieved significant technico-economic results. The fully mechanized mining technique used in gently inclined thin coal seams (the hardness being of less than mediam grade, the thickness of more than 1.1 m), inclined medium thick coal seams, gently inclined thick coal seams (3.5～4.0m) and steeply inclined thick coal seams (mined by means of the mining method with top-coal 'drawing) has achieved certain results and can be applicated in suitable coal seam conditions, but some problems with it have not been resolved yet, and it needs to be futher improved. For the top-coal drawing mining in gently inclined thick coal seams, the fully-seam mining in thick coal seams (5m), the fully mechanized mining in hard thin coal seams, the mining equipment is still in testing period. The hydraulic powered supports used in the conditions of I, II and III[-grade immediate roof and main roof can be considered being mature now, while the supports used in the conditions of IV-grade immediate and main roof are in the further developing period. Bisides, the technico-economic results of fully mechanized mining have a close relation with the mine production capacity according to statistic informations. So attention must be paid to making the mining technology match the mine production capacity.When equipping fully mechanized faces, it is prior to be considered for better conditions, such as stable roof conditions, gently inclined (less than 15。