Chengdu–Kunming railway

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 is 1,134 km long and traverses rugged terrain from the Sichuan Basin to the Yunnan-Guizhou Plateau. The line was built between 1958 and 1970, with much of the work coming during the Third Front campaign to develop industry in China's interior. Major cities along route include Chengdu, Pengshan, Jiajiang, Emei, Ebian, Ganluo, Xide, Xichang, Dechang, Miyi and Panzhihua in Sichuan Province and Yuanmou, Lufeng, Anning and Kunming in Yunnan Province.

Construction of a largely new double-track line started in 2010 and was completed on 26 December 2022. A northern section of the old line was called the Emei–Panzhihua railway, but since the completion of the new line has been called the Chengdu–Panzhihua (shortened to Chengpan) section of the line and a southern section was called the Yuanmou–Kunming railway, but is now called the Yuanmou-Kunming section of the line.

History
Planning of the Chengdu–Kunming railway began in 1952 with several routes under consideration. An eastern route would have run via Neijiang, Zigong, Yibin, Shuifu, Yanjin. Yiliang, Malong and Songming. A central route would have taken a similar route as far as Yibin and continued via Pingshan, Suijiang, Yongshan, Daguan, Qiaojia, Huize, Dongchuan and Songming. A western route would run via Meishan, Leshan, Ebian Yi, Ganluo, Xide, Xichang, Dechang, Huili and Guangtong. Soviet advisers recommended the central route as they considered the western route to be too difficult to build, because of its geography and geology, and that it could not be maintained because it would be prone to flooding, mudslides and earthquakes. Nevertheless, a committee headed by Zhou Enlai preferred the western route and this was eventually confirmed. It was considered to give access to important mineral deposits, passed through areas inhabited by ethnic minorities and had advantages for national defence. The eastern route was later used for much of the Neijiang–Kunming railway, which was completed in 2001. The central route has similarities to the route of the under construction Chongqing–Kunming high-speed railway. Construction began in 1958 during the Great Leap Forward and expanded to full-scale in 1964. Much of the construction occurred as a focus of the Third Front campaign to develop basic industry and national defense industry in China's interior; this campaign was accelerated when fears of possible American invasion increased after the Gulf of Tonkin incident. The only rail connection to Kunming at that time ran through North Vietnam. In July 1970, the line was completed and entered into operation in January 1971. Because it was built as part of the secretive Third Front campaign pursuant to the view that it had to be kept hidden from China's geopolitical rivals, completion of the railway was not announced or promoted.

The government published a pictorial in 1976 showing pictures of the construction and extreme terrain that required hundreds of tunnels and bridges. Building conditions were hazardous and 2,100 workers perished during the construction of the original line.

On August 30, 2000, the entire line was electrified.

Aside from Chengdu and Kunming, the old line had a total of 122 stations, although many of these are now closed for passengers and some for freight operations. Four stations on either side of the Jinsha River (Yangtze) crossing were inundated by the Wudongde Dam in 2020.

On 14 August 2019, a major landslide occurred near Adai station, killing 17 staff involved in rescue and disaster relief. After emergency repairs on the affected section, freight trains and daytime passenger trains resumed operation on 25 October and 2 December of the same year respectively. It was decided to build the 1.5 km Yandai Tunnel to avoid the landslide-affected section. The project started on 7 September 2019. It was suspended due to the 2020 Lunar New Year holiday and the impact of the Covid 19 epidemic. It resumed on 10 February 2020 and was completed on 9 March and 26 April.

Cultural significance
Academic Covell F. Meyskens writes that the Chengdu-Kunming railway serves as a symbol of the Communist Party's technical ability to remake the Chinese landscape in accord with its own vision, comparing its function in this regard to the Ten Great Buildings.

Sculpture
In 1974, an ivory sculpture commemorating the completion of the Chengdu–Kunming railway was presented as a gift to the United Nations and is displayed at the U.N. Headquarters in New York. The sculpture depicts the rail bridge across the Dadu River between two mountain peaks, with intricate details of passengers inside the train. The sculpture, 150 cm in length and 110 cm in height, was made from eight elephant tusks and weighs over 300 kg.

Railway junctions
The Chengkun railway is a major trunkline in China's railway network and connects with numerous other railway lines including:

Sichuan Province Yunnan Province
 * Chengdu: Baoji–Chengdu railway, Chengdu–Chongqing railway, Dazhou–Chengdu railway
 * Guangtong: Guangtong–Dali railway
 * Kunming: Shanghai–Kunming railway, Nanning–Kunming railway, Kunming–Yuxi railway

Natural Disaster Vulnerability
Four sections of the railroad which pass through the Niuri River Valley, Manshuiwan to Xichang of the Anning River Valley, Jinsha River Valley and Longchuan River Valley are under the exposure of the vulnerable debris flow and landslide. Soviet experts used to make a prediction that the railroad "will be turned into a pile of scrap iron by violent nature even after it is completed" in the route design stage; An Imagery Analysis Service Note published by CIA in October 1971 made a statement that "[the railroad] will undoubtedly require more than the normal maintenance because of the rugged terrain it passes through" based on the detection of at least two replacement works of the destroyed tracks caused by landslides in the first year of its operation.

Upon operation, major natural disasters did not occur in the Anning River Valley and Longchuan River Valley section due to the considered route selection and adequate protection strategies adopted. However, the section through the Niuri River Valley that had a faster river flow—due to its short, steep channel and unstable valley side slope—was not given sufficient consideration during the construction period. Multiple incidents of debris flow have occurred in the Niuri River Valley section especially between Niri and Suxiong and between Lianghong and Aidai.

New line
In the early 21st century, with local economic growth, the single-track Chengdu-Kunming Railway had become congested. In order to create more capacity, the line was replaced by a double track-line with longer tunnels and viaducts, although the original track was generally retained as one of the two tracks between Chengdu and Emei. The new line is 900 km long, with a design speed of 160 to 200 km/h and cost 55.2 billion yuan to build in total. Most of the new line runs near the old line, but on some sections of the route is significantly shortened and straightened. Therefore, the new line is nearly 200 km shorter than the old 1091 km line. Trains now take only about 7 hours from Chengdu to Kunming.

Work on the new line commenced in 2010. Double-tracking of the section between Hualongmen and Pengshan was completed in June 2017. The final 384 km-long section between Emei and Miyi was completed on 26 December 2022.

A northern section of the old line was called the Emei–Panzhihua railway (shortened to E-Pan railway), but changed on completion of the full line to the Chengdu–Panzhihua (shortened to Chengpan) branch of the Chengdu–Kunming railway. A southern section was called the Yuanmou–Kunming railway (shortened to Yuankun railway), but is now called the Yuanmou-Kunming section of the line. The section of the old line between Huapengzi (south of Panzhihua) and Huangguayuan (north of Yuanmou) has been closed and flooded by the Wudongde Dam.

The new line is designed mainly for freight. It is proposed that high-speed passenger services between Chengdu and Kunming will be provided by the Chengdu–Chongqing intercity railway (completed in 2015) from Chengdu to Neijiang North, the Southern Sichuan intercity railway (due to open in 2023) from Neijiang North to a new station in Yibin, and the Chongqing–Kunming high-speed railway (approved by the National Development and Reform Commission in 2019) from Yibin to Kunming.