城市空间结构是城市规划和发展的基础研究内容之一,特别是以城市群综合发展的区域经济体成为当前城市发展的主要形态,以首都北京为核心的首都圈则是其中具有代表性的城市群,许多学者将该区域作为城市格局研究的首选对象。本文针对首都圈"京津塘、京唐秦、京保石"三条发展轴线内的主要城市,从区域内城镇体系空间结构、道路基础设施空间布局、城市扩展动态分析三方面,对20世纪80年代末、90年代末、2008年三个时间段的城市空间结构演变进行了遥感分析。其揭示出首都圈三轴线城市空间发展变化规律,为北京世界城市区域建设和发展规划提供了依据。结果表明,三轴线城镇均沿中心城向外扩展,城市之间的空间扩展和集聚表现出明显的辐射效应和方向性,城市扩展空间形态日趋复杂。另外,三轴线城市发展也表现出差异性,"京保石"发展轴线上的城镇密度相对较大,"京津塘"发展轴线上的交通设施分布相对密集,城市扩展及变化的速度和规模最大,"京保石"发展轴线次之。

Urban spatial structure is one of the major research fields in urban planning and development. Currently, regional economies are becoming the main form of urban development in urban agglomeration comprehensive development. The capital circle is a typical city group, which has a center of the capital. Many scholars have selected this region as the objective for carrying out researches on urban pattern fields. In this paper we analyzed the major cities along "Beijing-Tianjin-Tanggu, Beijing-Tangshan-Qinhuangdao and Beijing-Baoding-Shijiazhuang" three axes of the capital circle based on remote sensing technology. The urban spatial structure from 1980s to 2008 is analyzed in three aspects, i.e. the spatial structure of the cities and towns system, spatial distribution of road infrastructure, and dynamic analysis of urban expansion. The three aspects of the dynamic urban expansion are discussed in detail, including the quantitative description of urban expansion and spatial variation, occupation of land areas for expansion characteristics, and the evolution trend of urban spatial form. The paper reveals the spatial law of urban development, and provides support for international city construction of Beijing and its regional development planning. The results show that all the cities and towns along the three axes extended from the center of the city. Expansion and concentration between the cities have showed significant radiation effects and directionality. Spatial patterns of urban expansion have been increasingly complex. At the same time, urban expansion and development along the three axes have been different. The cities and towns along south-west axis of "Beijing-Baoding-Shijiazhuang" have been the most densely distributed. The means of transportation along the axis of "Beijing-Tianjin-Tanggu" have been most developed. And obvious changes occurred in the scale and rate of urban expansion along the axis of "Beijing-Tianjin-Tanggu", followed by the south-west axis of "Beijing-Baoding-Shijiazhuang".