When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stra...When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stratum. This extremely thick rock bed, called a ＂main key stratum＂, will not subside nor break for a long time, causing lower fractures and bed separations not to close and gas can migrate to the bed separation areas along the fractures. These bed separations become gas enrichment areas. By analyzing the rule of fracture evolution and gas migration under the main key stratum after the deep protective coal seam has been mined, we propose a new gas drainage method which uses bore holes, drilled through rock and coal seams at great depths for draining pressure relief gas. In this method, the bores are located at a high level suction roadway （we can also drill them in the drilling field located high in an air gateway）. Given the practice in the Haizi mine, the gas drainage rate can reach 73% in the middie coal group, with a gas drainage radius over 100 m.展开更多
With the change and development of modern international new situation, some of the more traditional tariff barriers declining, green barriers to trade with their own unique and distinct era characteristic become the m...With the change and development of modern international new situation, some of the more traditional tariff barriers declining, green barriers to trade with their own unique and distinct era characteristic become the mainstream of the development of international trade today. Along with the Western Europe in some developed countries protect their existing markets, with the name of environmental protection and green trade protection measures, construction of the green trade barriers, so in practice to a certain extent seriously hindered the of some agricultural products sales and foreign trade credits. In this paper, starting from the factors and characteristics of green barrier produces, analyzes the causes of the green trade barrier of positivity and negativity, and contact our country agricultural product export and the present situation of the green trade barrier causes, analysis the reason of the thwarted by the green trade barrier, the feasibility of the agricultural development status in China, and puts forward some operable countermeasures, in order to adapt to the new situation of the development of foreign trade of agricultural products in China and good circulation.展开更多
基金Projects 2005CB221503 supported by the National Basic Research Program of China70533050 and 50674089 by the National Natural Science Foundation of China2005BA813B-3-06 by the National Tenth 5-Year Key Scientific and Technological Project
文摘When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stratum. This extremely thick rock bed, called a ＂main key stratum＂, will not subside nor break for a long time, causing lower fractures and bed separations not to close and gas can migrate to the bed separation areas along the fractures. These bed separations become gas enrichment areas. By analyzing the rule of fracture evolution and gas migration under the main key stratum after the deep protective coal seam has been mined, we propose a new gas drainage method which uses bore holes, drilled through rock and coal seams at great depths for draining pressure relief gas. In this method, the bores are located at a high level suction roadway （we can also drill them in the drilling field located high in an air gateway）. Given the practice in the Haizi mine, the gas drainage rate can reach 73% in the middie coal group, with a gas drainage radius over 100 m.
文摘With the change and development of modern international new situation, some of the more traditional tariff barriers declining, green barriers to trade with their own unique and distinct era characteristic become the mainstream of the development of international trade today. Along with the Western Europe in some developed countries protect their existing markets, with the name of environmental protection and green trade protection measures, construction of the green trade barriers, so in practice to a certain extent seriously hindered the of some agricultural products sales and foreign trade credits. In this paper, starting from the factors and characteristics of green barrier produces, analyzes the causes of the green trade barrier of positivity and negativity, and contact our country agricultural product export and the present situation of the green trade barrier causes, analysis the reason of the thwarted by the green trade barrier, the feasibility of the agricultural development status in China, and puts forward some operable countermeasures, in order to adapt to the new situation of the development of foreign trade of agricultural products in China and good circulation.
