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Urban sprawl is a complex economic and social phenomena and processes, in recent years, with the growing population, rapid economic development, and accelerating urbanization. Changes in the characteristics of urban sprawl increasingly significant, and trends that are difficult to control. Excessive urban expansion to stimulate the economy of the city, while also varying degrees of impact of urban land use efficiency, a more serious impact on the city's ecological environment. To strengthen the study of urban expansion and improve land utilization efficiency, improve land management practices, and to provide scientific and rational land resources sustainable utilization countermeasures and suggestions have positive practical significance and of strategic importance. The small city of Ya'an, Shuangliu and Qionglai as pots West being a rising power, continuous economic development, the rapid urban expansion, too fast urbanization and urban expansion to stimulate the city's economic expansion will affect the efficiency and effectiveness of urban land use. Therefore, the study of urban expansion characteristics and driving force, which has an important role and significance alleviate urban construction land demand pressure as well as scientific and rational planning and management of urban land use. Extended way, the land use structure according to the spatial and temporal characteristics of the three urban expansion, expansion intensity analysis of three different levels of economic development, urban expansion characteristics differences, to establish urban expansion index system of the driving force: the level of economic development, the value of the tertiary industry accounted for The value of the proportion of the tertiary industries, the size of the cities, the level of urbanization, industrial land, land for public facilities, residential land, non-agricultural population, expropriation of arable land used for urban construction land nine factors, analysis of its driving force, drawn mainly impact factor. The conclusions were as follows: (1) from the extended space-time expansion characteristics of the three cities in 1997-2007 the Shuangliu large amount of urban land expansion, 2003-2007 2007, the highest built-up area expanded 6.003Km ~ 2 / r speed 2007, urban expansion coefficient of up to 15.123, the city is a major expansion. Ya'an City Qionglai amount of land expansion in 2003-2007 to 1.28 Km ~ 2 and 0Km ~ 2 speed expansion, maximum expansion factor of 3.95 and 2.95, respectively, the total urban land expansion is relatively small, in a slow period. Belong to large-scale extension extension from the city extended type Shuangliu County, take up a lot of land in the suburbs, the lower the efficiency of land use. The Ya'an Qionglai belongs connotative extension to transform the old city. (2) 1997-2007 3 urban land use structure differences. Shuangliu County of urban land use change is the land of warehouse space, municipal utilities, green spaces, public facilities, land, residential land; Ya'an City, urban land use change land for public facilities, municipal utilities land, special land and warehouse space; Qionglai urban land use change in the larger roads and squares, municipal utilities, green space, residential land. Overall, small changes in the three cities is the transportation land, special land and green space. Based on national standards for various types of land: the proportion of residential land for 20-32%, 15-25% suitable industrial land, roads and squares 8-15%, 8-15% in the proportion of green space, from land-use structure Overall, Shuangliu County has far more than the standard seriously irrational land use structure, Ya'an City, less than the standard internal land use structure in the inefficient use of relatively reasonable Qionglai land use structure and efficiency. (3) three urban expansion intensity in different time periods and at different speeds, from the whole the Shuangliu extension strength and speed, fastest Ya'an City, followed by Qionglai minimum. (4) Urban expansion is a dynamic process, rather than a static ultimate goal. Urban expansion factors are many, can be attributed to the following aspects: natural factors, urbanization, city size, economic factors, environmental factors, policies and other factors, calculated and analyzed by impact factor analysis, draw the main factors affecting urban expansion as: the size of cities, the level of urbanization, non-agricultural population, economic development level. (5) Based on the above research, the paper proposes the countermeasures and suggestions of urban expansion: the development of rational urban expansion mode; strictly control the size of the population, to improve the quality of the population; to strengthen urban expansion planning efforts, the implementation of public participation; optimization urban space layout, improve the efficiency of urban land use.
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