| As the rapid development of China’s economic in recent years, the consumption rate of China’s bauxite resources has been much faster than the world average. Currently, China’s shallow bauxite resources are gradually exhausted, so the exploitation of bauxite resources begins to turn to the deep. The underground mining of the bauxite is just in its infancy; only a few bauxite mines still use traditional room and pillar mining method which is low productivity, low resource recovery rate and serious waste. Meanwhile, now fully mechanized mining technology in coal industry has been very mature. If this method can be applied to the underground mining of bauxite, it will greatly improve production efficiency and resource recovery. Therefore this paper puts forward the new technology of long-wall loosing blasting fully-mechanized mining which researches a series of technical problems of implementing this technology. Although the application of loosing blasting fully mechanized longwall mining technology to the non-ferrous metal ore has not yet a precedent, the use of mechanized mining of bauxite is bound to become a general trend.The paper takes the underground mining of bauxite in Hejiagetai in Xing county as the main research object, using field sampling, laboratory test, theoretical analysis, numerical simulation, comparison and selection methods and field test and so on, researching systematically occurrence state, development and distribution of geological structures, ore characteristics, mining methods of bauxite ore layer in Hejiagetai.It proposes a new method of underground mining of bauxite, namely loosing blasting fully mechanized longwall mining technology of the bauxite, exploratory research of the loose blasting, strata pressure control and equipments have been launched, which support this method. The main results are as follows:(1) By site coring and laboratory tests, we clear the distribution of the roof and floor rock, and physical and mechanical properties of the rock, which offers the basic theory to the reasonable choice of the underground mining of bauxite mining method.(2) In connection with the occurrence state of bauxite in Hejiagetai and with the basic principles of mining design, scientifically and rationally analyzing the underground mining method of bauxite in Hejiagetai, we establish that the mining methods are room and pillar mining and long-wall single caving, and put forward creatively a new method:long-wall loose blasting fully-mechanized mining. Combined with theoretical analysis, we establish the main technical parameters extraction technology of the various mining methods. By comparison, long-wall single caving method and long-wall loose blasting fully-mechanized mining have larger face production, higher production and recovery efficiency, more obvious economic benefits than room and pillar mining. Its advantages are far more than any other mining methods.(3) On the basis of analyzing the rock crushing mechanism and the strength characteristics of fractured rock, we regard the rock mass strength of the nature of the fractured rock as an evaluation of the cutability of the ore, which can be calculated by measuring the transmission speed of the ultrasonic wave in ore. Thus, the cuttability evaluation of the loose blasting rock can be solved(4) On the basis of studying the distribution of the jointed rock mass and blasting fragmentation, we propose the regression analysis of determining the relationship between blasting fragmentations and blasting parameters, which provide the basis on the blasting parameters which are determined by the blasting fragmentation requirements. And we also propose the calculation method of loose blasting parameters against the underground mining conditions in Hejiagetai by the analysis of loose blasting principle.(5) By the field bursting test and the cuttability evaluation and method of the loose blasting rock, we evaluate and analysis the blasting effect. We conclude that the ore strength can be weakened to1/4of the rock strength. To the bauxite in Hejiagetai, the bauxite strength is87.64MPa and the strength can be reduced to21.91MPa after reasonable loose blasting. Because of the test results, the drum mining machine can be used in the bauxite mining, which provides a realistic basis for the realization of long-wall mechanized mining in bauxite.(6) We study the basic forms of the stope roof structure and strata characteristics by long-wall mechanized mining in bauxite.(7) Against the occurrence state of the roof and floor of the bauxite in Hejiagetai, using synthetically immediate roof load factor estimates, theoretical calculations, numerical simulation analysis method, we determine the reasonable support strength of hydraulic support by long-wall loose blasting mechanized mining, and the strength is not less than0.56MPa. Meanwhile, we solve problem that loose blasting rock may damage the support column by designing the smashing device of the hydraulic support column.(8) The roadway characteristics of the bauxite mining area in Hejiagetai is "two soft and a hard". In connection with the surrounding rock strength characteristics of this roadway, we get the roadway solutions and support parameters of mining face by long-wall loose blasting mechanized mining in Hejiagetai. (9) Through the equipment selection and overall design of the bauxite mining face by long-wall loose blasting mechanized mining, determining the drum mining machine, face scraper conveyor, crossheading transfer machine and crusher, crossheading scalable belt conveyor, it provides the main technical and security for the realization of the safe and efficient mining of the bauxite by long-wall loose blasting mechanized mining.In conclusion, by more in-depth and systematic study of long-wall loose blasting fully-mechanized mining technology of the bauxite in Hejiagetai, we solve the main technical challenges of the fully-mechanized mining of the bauxite, which provides a scientific basis on the fully-mechanized mining and design of the bauxite. |
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