1936年以来南京城市空间扩展特征研究

城市交通网络的发展是城市空间扩展的重要表征和驱动力。以1936—2015年间6个代表性年份的城市交通地图为数据源,提取相应年份南京城市轴线图,利用基于空间句法的整合度、城市扩张强度（SS-EII）和智能度指数,分析1936年以来南京城市空间扩展趋势和特征,划分演化阶段,并分析城市加速扩张阶段的空间扩展质量。结果表明：① 南京城市空间扩展大体经历了滞缓（1936—1971年）、复兴（1971—1982年）和加速（1982—2015年）三个阶段,逐渐突破老城区,向西南、东北、南部和西北实现全方位空间扩展,形成多中心空间结构。② 加速阶段空间扩展质量总体较高,交通网络建设逐渐与用地扩张相协调,并开始引导城市空间多中心扩散,但各中心间有机联系不足,导致城市空间整体性和空间效率有所降低。③ 应进一步加强多中心间的交通联系,促进人口、经济有机疏散,并提高城市空间整体性。

The characteristics of urban spatial expansion in Nanjing since 1936

The development of urban road network is one of the main driving forces of urban spatial expansion. Based on the urban traffic maps in 1936, 1949, 1971, 1982, 2001 and 2015, the urban axis maps of Nanjing were extracted for the corresponding years. With the Integration Index, Urban Expansion Intensity Index (SS-EII) and the Intelligence Index, which are all based on spatial syntactic analysis, the trends, characteristics and evolution stages of urban spatial expansion in Nanjing from 1936 to 2015 were analyzed, and the spatial expansion quality at the accelerated expansion stage was discussed. The results are as follows: (1) In the 80 years, the urban road network of Nanjing has been integrated into a whole from the original regional isolation, and the primary and secondary roads tend to be clear and neat. The early urban area was composed of Xinjiekou as the single center, and along the north-south, east-west and northwest major roads respectively, the urban area gradually expanded, forming a multi-center spatial structure. (2) The urban spatial expansion in Nanjing experienced three stages, that is stagnation (1936-1971), revival (1971-1982) and acceleration (1982-2015), and achieved an all-round expansion to the southwest, northeast, south and northwest. At the stagnation stage, the urban space maintained one single center, mainly along the northwest, southeast and northeast axes, there was slow infilling within the old urban area. At the revival stage, the urban space broke through the boundary of the Ming City Wall to expand in four directions, and some small-scaled regional centers gradually appeared in the northwest and south of city. At the acceleration stage, the urban space greatly expanded along the northeast-southwest and northwest-southeast axes, resulting in the urban multi-center structure. (3) At the acceleration stage, the quality of spatial expansion was generally high. The construction of transportation network followed the expansion of urban land use, and gradually caught up and matched with it, even begun to lead the directions of multi-center diffusion in the city. However, due to the lack of traffic links among the multi-centers, the integrity and spatial efficiency of the urban space generally declined. In summary, the general trends and characteristics of long-range and large-scaled urban spatial expansion can be reflected by analyzing the evolution of road network and SS-EII, and the urban multi-centers and their evolution can also also accurately extracted. Compared with L-EII, R-EII and the Intelligence Index, the quality of urban spatial expansion can be also evaluated. In view of the current lack of links between urban multi-centers, in the future, the traffic links between the urban centers and the sub-centers, as well as between the sub-centers, should be further strengthened, so as to improve urban traffic efficiency, organically decentralize the urban economy and population, as well as improve the organization integrity of urban multi-centers. In the future study, further considerations should be given to the impact of road attributes and subway networks on the topological relationship of the axis map and the accessibility of urban space.