【正文】 ick and extrathick coal seams can not only prevent spontaneous bustion 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 doubleentry system into singleentry system, thus the developingextracting ratio decreased. At the mean time, developing mechanized mining to ease the hard labour works was paid much attention by the government. The MLQ64 type shallowweb single drum shearer, which was made out in Xiaohengshan Coal Mine (Jixi CMA), bined with SGW44 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, and 遼寧工程技術(shù)大學(xué)畢業(yè)設(shè)計(jì) 3 the degree of mining mechanization raised from % at the end of 1st 5Year plan to % at the end of 3rd 5Year 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, plete 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 reforming and opening, more than 100 sets of fully mechanized mining equipment were imported and wideranging international exchanges were in progress, which speeded the researches of homemade 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 11. Latter, the newly manufactured MLQ280 type, DY100 type and DY150 type single drum shearer, MLS3p170 type doubledrum shearer replaced the MLQ64 type, MLQ280 type single drum shearer, the new SGW150 type chain scraper conveyor replaced the SGW80 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 technioeconomic results. After that, the new MG150W1type doubledrum 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 technicoeco nomic results. At the same period, the blasting mining technology of longwall faces developed new techniques, such as the blasting with millisecond delay detonator, the blastingproof type individual hydraulic props the doublespeed 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 topcoal drawing and the corresponding mining technology have been studied and tested since 1982. The first set of equipment for fully mechanized mining with topcoal drawing was tested in the gently inclined extrathick coal seam of Puhe Coal Mine (Shenyang CMA) in June of 1984. In April of 19839。遼寧工程技術(shù)大學(xué)畢業(yè)設(shè)計(jì) 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 dev