World’s longest expressway tunnel opens in China at an altitude of 9,842 feet

The Tianshan Shengli Tunnel, a 13.75-mile (22 km) long tunnel at the center of the Urumqi-Yuli Expressway, and the world s longest, is now open in China. Constructed over five years using innovative approaches, the tunnel halves the travel time between the regional capital, Urumqi, and the city of Korla to 3.5 hours, state media reported.

In the past few decades, China has undertaken some of the largest infrastructure projects in the world. From the 22.5 gigawatt hydroelectric power plant at the Three Gorges Dam to the Pinglu Canal, which provides an inland-to-sea connection for large ships, China is making huge leaps in the ambition of its projects.

Interesting Engineering has previously reported how the Asian giant is also using its deserts to field large-scale solar power plants, and the Belt and Road Initiative (BRI) looks to connect the nation with Africa and Europe through a network of new railways, ports, and roads. The Tianshan Shengli Tunnel might seem like a minor project compared to these mega projects. However, it is still a significant achievement for the local region and set world records during construction.

Where is the tunnel? The tunnel is located in the Xinjiang Uyghur Autonomous Region and facilitates a drive through the Tianshan Mountains. The region shares borders with eight countries, including Kazakhstan, Kyrgyzstan, Tajikistan, and Pakistan, facilitating connections to Central Asia. Before the expressway, travelling between Urumqi and Koral would take nearly seven hours.

But now the travelling time will be reduced to 3.5 hours. Additionally, it connects the region to various economic corridors across the country, aligning it with the national dual circulation strategy, which seeks to integrate domestic and foreign trade.

Work on the tunnel began in April 2020, but engineers faced challenges with terrain and environmental conditions during construction. Innovations in its construction The tunnel runs through the Tianshan Mountains at an altitude of 9,842 feet (~ 3,000 meters) above sea level. Temperatures at these altitudes reach a bone-chilling minus 43.6°F ( minus 42 °C). Attempting to construct an expressway using conventional methods would have taken Chinese engineers at least a decade to complete, the chief engineer of the Xinjiang Transport Investment and Development arm told local media.

So, the engineers used a novel three tunnels plus four shafts strategy during the construction. Instead of trying to build a long, deep main tunnel, the engineers dug three tunnels: the main one and two parallel ones. The parallel tunnels facilitated geological investigation ahead of the main bore and provided workers with access to the site and equipment. In emergencies, the third tunnel could be used to house ventilation systems and serve as an emergency escape route.

The four shafts were vertical passages dug from the surface to the tunnel depth. Shafts nearly 2,300 feet (700 m) deep were dug and served as additional entry and exit points, allowing work to proceed in parallel rather than at just two ends.

In addition to being the world s longest expressway tunnel, the construction also holds the world record for the world s deepest vertical shaft for a highway tunnel. Reduced travel between the two regions will facilitate the flow of energy and manufactured goods to the north and agricultural goods to the south, the South China Morning Post reported.