The 12.3 kilometre Xinhua Tunnel, part of the Dali-Lincang Railway, was successfully connected on Tuesday. This is the first tunnel of such length to be constructed in the Hengduan Mountain Range in Southwest China’s Yunnan Province.

An expert said the project will be hugely beneficial to local economic development.

Construction work for the entire project started at the end of December 2015, and it is expected to be completed by the end of June 2021. After completion, Lincang will finally be connected to the country’s rail network.

It will take just three hours to reach Lincang from Yunnan’s capital Kunming, improving the overall transportation system in the remote central and western parts of Yunnan. The railway will improve transportation connections between China and adjacent countries.

Transportation will be of great significance to the local economy in Yunnan, especially by connecting the province to neighbouring economies that are part of the Belt and Road Initiative, Tian Yun, a Vice Director of the Beijing Economic Operation Association, said on Wednesday.

The entire Dali-Lincang Railway is 202 kilometres long with a top speed of 160 kilometres per hour. It is a national I-class electrified railway. Located in Nanzhang county, the Xinhua Tunnel is one of the most difficult projects along the route.

Obstacles during the construction process included high water pressure, high geothermal heat, high seismic intensity and high ground stress.

The tunnel passes through three faults, and temperatures inside the tunnel can exceed 40 C. To ensure the safety and normal operation of construction machinery, two 370 kilowatt super-powerful fans and about 10 tons of ice were used daily to reduce the heat.