Another effective method to cool the permafrost is to install a block stone layer in the embankment or on a slope. In winter when surface temperature dips lower than that of the permafrost, natural air convection occurs in the block stone layer, removing heat from the permafrost. Meanwhile, a series of other cooling methods have also been adopted, including sunshine-shielding devices and crushed-rock revetments.

A number of check stations have also been set up along the railway line to monitor temperature changes in the permafrost and ensure the absolute safety of the tracks, Zhang Luxin, a permafrost expert who participated in the railway construction, said in an interview with the Beijing News.

Designers tried to make a detour around the most unstable permafrost area, or build bridges to avoid permafrost when necessary, he added.

The challenges brought by the permafrost don't end there. They also made it difficult to build tunnels such as the Fenghuoshan Tunnel, the highest of its kind in the world. Tunnel blasting produces high-temperature and high-pressure gases that may disrupt the heat balance of permafrost, causing landslides. To offset this, the engineers developed a series of advanced technologies, such as air-conditioning and installing a heat-insulation and waterproof layer on the tunnel walls. They also used brine mud to plug the blast holes to cool the explosive gases.

Another head-scratcher facing the builders was how to protect the vulnerable Tibetan ecosystem, including the vast wetlands and a variety of wildlife. To minimize damage to the wetlands, engineers fostered artificial wetlands by the side of the railroad and then transplanted the turf dug up for construction to the artificial area. Moreover, 33 bridge-like special safety channels were built to allow free migration of Tibetan antelopes and other wild animals.

"The passage is a last resort in wild animal protection-it is a compensatory measure granted by humans to animals," Yang Qisen, a zoologist with the Chinese Academy of Sciences, said in a statement.

Since the railway crosses hundreds of seismic belts on the plateau, earthquake prevention efforts are important for its smooth operation. As much as possible, the railway line has sought to meet the seismic belts at right angles and avoid using tunnels and bridges, which are particularly vulnerable to tremors. With those efforts, the railway has survived a number of disastrous quakes including the Kunlun earthquake, measuring 8.1 on the Richter scale, which struck on November 14, 2001.

Roaring ahead

While the Qinghai-Tibet Railway winds its way through mountains and wetlands, the Beijing-Tianjin intercity railway impresses more with its lightning speed. It shortens the rail journey between the two cities to half an hour, carrying passengers at a top speed of 350 km per hour on special bullet trains with spacious and plush interiors.

A glimpse at its domestically manufactured CRH-3 (China Railway High-Speed) trains explains how they glide along so effortlessly. Their streamlined shape minimizes air resistance, and the train body, made of aluminum alloy, features low noise, high durability, and weighs about 30 percent less than ordinary ones. More importantly, the high-speed trains are equipped with multiple engines embedded inside separate units, instead of being driven by a single engine. Their total power output is 8,800 kw, which was achieved by distributing multiple traction motors underneath the whole train. They are also equipped with an advanced and reliable brake system and a high-speed bogie.