The Chengdu–Kunming railway or Chengkun railway (), is a major trunkline railroad in southwestern China between Chengdu, the capital of Sichuan Province and Kunming, the capital of Yunnan Province. The line runs through the Dadu River and Anning River basins in southwestern Sichuan, which are enclosed by high mountains, canyons and major rivers, and the basin in northern Yunnan. It crosses a major geological fault zone. The mountains along the line are steep and the terrain and geology are extremely complex.
The idea of building a railway between Chengdu and Kunming originated in the late 19th century, but concrete surveys were not conducted until the 1930s and 40s. However, the project was ultimately thwarted by the rugged mountains between Sichuan and Yunnan provinces. Surveys began in the early 1950s, and after comparing and evaluating three main route options—western, central, and eastern—the western route was ultimately chosen due to factors such as the Panzhihua steel base and the natural resources along the route. Construction began in the summer of 1958, but was halted after the completion of the Chengdu-Qinglongchang section in early 1960. Construction resumed in 1964 as a key project of the Third Front construction. The Cultural Revolution subsequently hampered progress in the section under the Second Railway Bureau, but normal construction resumed at the end of 1969. The entire line opened to traffic on 1 July 1970 and began operation on 1 January 1971.
The definition of the Chengdu–Kunming Railway route has undergone several changes. Since 29 September 2021, China Railway has designated the Chengdu–Yizi section as the "Chengdu–Panzhihua Section of the Chengdu-Kunming railway," the Huangguayuan–Kunming section as the "Yuanping–Kunming section of the Chengdu–Kunming railway," and the newly built double-track section originally between Emeishan and Guangtong, now part of the Chengdu–Kunming railway, as the . After the Emeishan–Guangtong railway fully opened to traffic on 26 December 2022, the section of the existing Chengdu–Kunming railway south of Emeishan mainly serves freight and short-distance passenger transport. Currently, three pairs of public-service slow trains operate daily along the entire Chengdu–Kunming railway, with two pairs passing through the Liangshan area becoming a vital lifeline for local residents.
The Chengdu-Kunming railway passes through areas rich in various mineral deposits, and the Dadu River, Yalong River, and Jinsha River basins along its route possess abundant forest and hydropower resources, showing great potential for development. Furthermore, the line traverses areas inhabited by ethnic minorities in Southwest China, playing a significant role in improving transportation conditions, strengthening ethnic unity, promoting economic development, and advancing national defense in the region. Because the Chengdu-Kunming Railway traverses rugged mountains, many construction workers lost their lives during its construction, and several martyrs' cemeteries exist along the railway line to commemorate these sacrifices. During operation and maintenance, the line has also been repeatedly affected by natural disasters, resulting in accidents. This arduous journey has also given rise to the "Chengdu–Kunming Spirit." Today, some bridges, tunnels, and sections of the railway along the route have been designated as cultural relics protection units by the local governments, such as the "Renhe section of the Chengdu–Kunming railway."
Route The Chengdu-Kunming Railway starts from Chengdu, Sichuan in the north and ends in Kunming, Yunnan in the south. The actual length of the line is and the operating length is . In terms of technical requirements, the line exceeds the standard of the existing railway trunk lines in Southwest China: the restricted gradient is 0.6%,The maximum allowable gradient for a section of track hauled by a single locomotive. the gradient north of Xichang reaches 1.6%,The maximum allowable gradient for sections pulled by two or more locomotives. and the gradient south of Xichang reaches 1.2%. The minimum curve radius in general sections is , and in difficult sections it is . Only a few curves with radii of and are retained between and due to the consideration of future rerouting. The entire line was initially a single-track railway and diesel locomotives were used to haul trains. The tunnels were designed for electrified railway clearance, and the design of the line between Guangtong and Kunming provided for the construction of a second track, After the completion of the Chengdu–Kunming double-track railway and renovation project, the section from Chengdu to Emei (specifically to ) and the section from Wenquan to Kunming was rebuilt as a double-track railway with an operating speed of .
The Chengdu–Kunming railway crosses mountains four times, passes through spirals seven times, crosses the thirteen times, crosses the Anning River eight times, and crosses the Longchuan River and its tributaries, the Chuxiong River and the Guangtong River forty-nine times. When the line was opened to traffic, there were 427 tunnels and open-cut tunnels and 991 bridges, with a total length of , accounting for 41.6% of the total length of the line. Among them, the was the longest tunnel built for a railway in China at that time, and the steel truss and the stone arch were also the largest spans of their kind in China at that time.
The line connects with some other railway trunk lines in China's railway transportation network: in Chengdu it connects with the Baoji–Chengdu railway, the Chengdu–Chongqing railway and the Dazhou–Chengdu railway; in Kunming it connects with the Shanghai–Kunming railway, the Nanning–Kunming railway and the Kunming–Hekou railway, and in Guangtong it also connects with the Guangtong–Dali railway.
Overview of the route The Chengdu–Kunming railway originates from Chengdu, passes through the Chengdu Plain at an altitude of about , and then goes south through Pengshan, Meishan, and Jiajiang. Starting from Emeishan, it goes up the left bank of the Dadu River valley, passes through Ebian Yi and Jinkouhe, and then turns into the Niuri River valley. It passes through Ganluo and , and uses the Shamalada Tunnel at an altitude of to cross the watershed and go down the Sunshui River. It passes through Xide and , and then turns into the Anning River valley to reach Xichang. From Xichang, it continues down the Anning River and Yalong River, passes through Dechang and Miyi to the Jinsha River valley at an altitude of about . After that, it goes up the Longchuan River valley, passes through Yuanmou, Lufeng, and Anning to reach the Yunnan Plateau at an altitude of about where Kunming is located.
The railway has a complex and rugged terrain. There are cliffs hundreds of meters high in the valleys of the Dadu River and Jinsha River, and several sections of steep riverbeds in the valleys of the Niuri River and Sunshui River. In terms of geology, the area along the line has been affected by the geological tectonic movements of the past, and new geological tectonic movements are also active, resulting in various adverse physical and geological phenomena. More than of the line are located in the seismic zone of intensity 7–9. The industry has always used the term "geological museum" to describe the complex geological conditions along the line. In addition, due to the influence of the location, region, and altitude, the climate of the areas through which the line passes is diverse: the Sichuan Basin is a hot and humid climate, but the valleys of the Dadu River and Jinsha River are a hot and dry climate, while the Yunnan Plateau is a mild climate. Therefore, in the process of completing the project, both the survey and design and the construction of the project faced great difficulties.
Construction process Background
As early as the end of the 19th century, the United States, Britain, France and other countries planned to build a railway connecting Sichuan and Yunnan provinces, and some countries also conducted surveys. During the Second Sino-Japanese War in the 1930s and 1940s, the Nationalist government wanted to ensure transportation in the southwest region and also conducted some surveys on the line. After comparison, the Ministry of Communications selected the route through Yibin (then called Xuzhou), Fuzhen, Yiliang, Weining, Xuanwei, Qujing and Kunming, and established the Xukun (Xuzhou–Kunming) Railway Engineering Bureau to conduct preliminary surveys and preliminary construction of the line. However, the terrain of the section through which the line passed was steep and the geology was complex, and the project was ultimately not implemented. By June 1944, the Xukun Railway had only completed track laying between Kunming and Zhanyi.
After the founding of the People's Republic of China, the newly established Central People's Government needed to build domestic infrastructure. In 1952, while carrying out the Baoji–Chengdu railway project, the Ministry of Railways also began to study the route of the Chengdu–Kunming railway. In April of that year, the Southwest Design Bureau of the Ministry of Railways began to conduct preliminary surveys (draft surveys) of the line. The survey covered the area between Chengdu and Kunming, with a length of about and an average width of about .
The proposal of three major plans for the entire route
The preliminary survey was completed in April 1953. After the scheme study and preliminary survey, the Southwest Design Bureau proposed three route schemes for the entire line: an eastern route, a central route, and a western route. The routes of the three schemes were as follows:
The eastern route started from Chengdu, sharing the same line as the Chengdu–Neijiang section of the Chengdu–Chongqing railway. From Neijiang, it branched off the railway, heading south-southwest through Zigong, Yibin, and Anbian into Yunnan Province. Following the Guanhe River, it passes through Yanjin, Daguan, Yiliang, and Zhaotong, entering Guizhou Province at Weining County. It then re-enters Yunnan Province, passing through Xuanwei, Zhanyi, and Qujing before turning west, passing through Malong, Xundian, and Songming to reach Kunming. The eastern route was .
The central route option started from Chengdu, sharing the same line as the Chengdu–Neijiang section of the Chengdu–Chongqing railway. From Neijiang, it branches off the Chengdu–Chongqing railway, heading south-southwest through Zigong and Yibin, then turning west through Pingshan, crossing the Jinsha River into Yunnan Province via Suijiang, Yongshan, Daguan, Qiaojia, Huize, Dongchuan and Songming, finally reaching Kunming from the north. The central route option was .
The western route started from Chengdu, passing through Meishan, Leshan, Ebian, Ganluo, Xide, Xichang, Dechang, Huili and Guangtong, ending in Kunming. The western route was .
Solution selection