| China is abundant in coal resources, and coal has been the main energy consumption for a long time. However, the coal production pattern deviates from the consumption pattern severely, which gives rise to high-intensity and large-scale flow of coal resources. Railway is the primary means of coal transportation, but the increasingly growing coal resources flow results in longer and longer coal transportation distance, as well as larger and larger traffic volume. China’s coal railway transportation network has been through thirteen decades of development, and as a result, tremendous breakthrough has taken place in the density of road network, transportation equipment, as well as the operations management, forming six regional coal railway transportation network, including northeast, north China and east part of northwest, east China, middle of south and southern part of China, southwest, and Sinkiang. However, China’s rail tracks is short in mileage and uneven in road network distribution, with few railroad transportation networks between the regions, low railway technology, mixed transportation of passenger and freight train, variety of freight categories, and huge transportation pressure.Under such a circumstance, three time nodes are selected in this paper, namely the fifth national railway speed increase in2004, the sixth railway speed increase in2007and the preliminarily formation of China’s high speed railway in2011, for studying on the reachability of large-scale key mines in China and the reachability evolution of coal railway transportation network in China respectively, discussing the development mechanism and proposing optimization suggestions.In this paper, the reachability development of78national key coal mines in China is studied with grid method, and according to the results, the reachability distribution of key large-scale mines in China is related to the position of coal mines and railway network, with strong traffic directivity and obvious differences. Regions with good reachability are near the key large-scale national coal mines. From2004to2011, the time distance of Zhejiang, Hubei, Fujian, Guangdong, Guangxi, Baicheng in the west of northeast China, Da’an was shortened, with good reachability. However, reachability of the west part in Sinkiang and Tibet is not optimized. Grid method only studies the time distance of any point to the nearest target point through the transportation network, but in practice, coal transportation conditions of’seeking far and neglecting what lies close at hand’ spreads widely. Studies on the reachability based on ’human’ displacement give few considerations to the transfer, but it shall be considered in the coal transportation, and this is the deficiency of grid method in studying the reachability of coal transportation. Consequently, in this paper, distance method is adopted, and the reachability development of large-scale key coal mines is studied with the shortest spatial distance, weighted transit time and connectivity. Among the three characteristic years, coal mines in Henan always have a best shortest spatial distance, which is in circular distribution, with gradually decreasing reachability level. The reachability differences of southwest coal mine is shortened at first, and there are no obvious changes, while there are no obvious changes in the spatial reachability of northeast coal mine, suggesting that the coal transportation network pattern and coal mine location is the leading influencing factors of shortest spatial distance. The weighted average transportation time distance contour line of year2004is closed circle, while2007became’C type, opening to the East China, and2011became closed circle again. The weighted average transport time in southwest region, east Gansu and northeast Inner Mongolia is relatively long, with poor availability, but the difference of weighted transport time between north Inner Mongolia and Erdos mines gradually decrease, and the time reachability is balanced. The most primary cause for the changes in time reachability lies in the transition of China’s railway construction and operation policies from existing line to passenger and freight separated lines. Owing to the optimization of locomotive routing, the connectivity contour line gradient decreases, suggesting that the connectivity difference of large-scale state-owned coal mine is declining.The reachability evolution characteristics of coal railway transportation network is analyzed with the shortest spatial distance, minimum time distance, connectivity and reachability coefficient by taking the marshalling station and coal water port involving the coal transportation in railway network as the nodes. According to the results:(1). From2004to2007, by transforming the existing railways simply and improving the highest running speed of the train, it not only failed to reduce the journey of coal transportation, but also lowered the time reachability in north China, north part of east China and south China due to the addition of high-class passenger trains.(2). The spatial distance reachability occurs in a center-periphery pattern with north of Zhengzhou as the center; the core of the layer of time-distance reachability experiences displacement and deformation, for instance, it was circular with north of Fuyang as the core in2004, while it was stretched in long and narrow shape in2007, and it was expanded in oval shape in2011:the core layer of the connectivity expands in north and south direction in2004, while it became the’L-shape’extension in2007, and ’cross-shape’ in2011;(3). China’s coal railway transportation network grows balanced day by day, and its connectivity is the most balanced, and then it is the time distance and spatial distance.(4). In the coal water port, location is a crucial factor determining the reachability.Factors influencing the coal railway network reachability consist of the internal factors of railway and external factors of railway. The internal causes contain the level and technical standards of coal railway, contradictions between the passenger rail transport and the coal transportation, management system of railway, etc. while the external causes contain the changes in production capacity and coal consumption, adjustments in the policies of railway construction and operation policies, etc. According to the above influencing factors, the mechanism of reachability evolution of coal railway transportation network is discussed, including motive power-changes in the coal production pattern; pushing force-namely constant perfection of railway network by increasing the investment; support force-constant improvement of the performance of railway transportation device with science and technology, as well as the constant innovation of railway transportation management system; pressure passenger transport demands, as well as some human factors, etc. as for the transportation of passenger and freight separated line, four modes are proposed, namely Zhengzhou-Xi’an, Beijing-Shanghai, Shijiazhuang-Taiyuan, as well as Jinan-Qingdao railway. In which, Shijiazhuang-Taiyuan and Jinan-Qingdao railway are the most favorable for improving the reachability of coal mine, Beijing-Shanghai railway considers both the long-distance passenger and coal transportation, while Zhengzhou-Xi’an railway is limited in improving the reachability of coal.According to the Medium and Long-term Planning for Railways in China, China’s large-scale national coal mines and reachability of coal railway transport network in2020are predicted respectively. Compared to2011, the reachability of most large-scale coal mines will be optimized in2020, and the improvement of coal mine reachability in the east of the northwest is the most evident, owing to the newly-built cross-regional coal transport special railway line, as well as the perfection of internal coal transportation railway network, and then it shall be Xinjiang region. Generally, the reachability of coal railway transportation network in2020will be optimized, and the improvement of reachability in northwest region and Fujian area is evident, while that in southwest and northeast region is relatively limited. With the promotion of long locomotive routing, the connectivity difference of each region is narrowed evidently. According to the conclusion of the previous studies and the prediction results, the following suggestions are proposed for the reachability of China’s coal railway transport network:firstly, the coal railway transportation network shall be perfected and optimized constantly, and recently, attention shall be paid to the construction of coal transportation network in the east part of northwest region and Xinjiang region for adapting to the increasingly growing demands for coal transportation. Secondly, it shall stick to the ’passenger-freight separated line’, perfect the passenger special line network, optimize the passenger transport organization, and make room for more operation space for the coal trains. Furthermore, it shall continue to promote the coal train transportation and locomotive routing, and launch the joint operation of national railway and enterprise coal railway. Finally, it shall make full use of the returning empty coal train, and launch ’pendulum model’transportation. |
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