The Chinese government has been building a $1.2 trillion new tunnel to transport goods and people between the country’s two biggest cities of Beijing and Shanghai.
But a recent test tunnel in western China’s Liaoning province is showing a new vulnerability that could make it harder to build the $16.5 billion tunnel and a similar one in eastern China’s Inner Mongolia Autonomous Region.
The test tunnel, which was built to accommodate up to 20 million passengers a day, was tested on March 18 in the town of Zhongshan, about 120 miles (190 kilometers) north of the city of Chongqing.
The tunnel, with a diameter of 2,000 feet (610 meters), is part of a project that is expected to cost $1 billion and is under construction in the city’s central railway station.
Construction of the new tunnel began in January 2017 and is expected be completed in 2021, according to China Railway Engineering Corporation, which is building the tunnel.
The new tunnel, however, is vulnerable to a series of structural defects that could cause major damage if not repaired, the agency said in a statement.
The problems included cracks, wear on the steel-and-plastic casing and cracking.
The agency said it was also concerned about an area that is under a rock formation that can trap air bubbles.
The tests took place between June and September, the Xinhua News Agency reported.
The tunnels are meant to accommodate an average of 15 million passengers per day, according a company official quoted by the agency.
The project is being built with China’s largest tunnel boring machine, the 663-metre-long (1,500-foot-long) CGN-1, which can deliver 8,000 tons (3,600 metric tons) of tunnel per day.
China’s state-owned China Railway Corporation said it did not know how long the tests took and said it could not provide any information about the results.
The company also did not respond to a request for comment.
Construction in western Liaoning and the Inner Mongolia are expected to be completed by 2022.
The Xinhua news agency said the test tunnel was part of the construction of a 1,500 km (620-mile) high-speed rail line that would connect the two cities.
It said the project was set to be extended to Beijing and that the tunnel had been completed.
China also has a long-standing infrastructure project, the Beijing-Tianjin-Hebei High Speed Rail Link, or Beijing-Xianggang-Hebao High Speed Railway, or BHHS-HSS, to link the two provinces.
The government has set up a $50 billion fund to finance the project.