Chinese engineers have used an innovative underground nitrogen system to build China's recently opened Beijing-Lhasa railway line.

The system was used as the ground chosen for the building project was in places covered with permafrost that would need to remain firmly frozen to ensure the tracks structural integrity. To deal with this problem the authorities commissioned the design of a system of underground piping that uses solar power to circulate both liquid nitrogen, and nitrogen gas over the 180km stretch to keep the ground cool and solid.

However, innovative as the idea is there are some signs that its application may be misplaced. The national news agency has reported that in some sections, the concrete in the rail bed has developed surface cracks, and foundations are sinking into the permafrost.

The Chinese Governemnt have played down the potential problems and the Ministry of Railways Vice Minister Song Yongfu has simply said that the ministry would take measures to deal with such difficulties.