【正文】 遼寧工程技術(shù)大學(xué)畢業(yè)設(shè)計 1 The method of mining in China The Known coalbearing area is about 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 coalbearing 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 %, of mediun thick coai seams for %, of thick coal seams for %。 As considering the inclination of coal seams, the amount of reserves of gently inclined coal seams accounts for %, of inclined oal seams for %, of inclined seams for %. 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 inplete 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 pleted 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 longwalltype 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 the 曹野： 2 Coal 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, highface stoping caving method was changed into the downward inclined slicing with topcoal retained or under the protection of false timber roof, the downward horizontally slicing caving method with false topcoal 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 %, 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 topslicing 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 metalmesh 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 pressed air hammer was tested at the beginning, then tongwall mini ng 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 sh