High-speed rail has become the absolute main railway Spring Festival. At the end of 2018, the operating mileage of my country's high-speed railways exceeded 29000 kilometers-more and more high-speed rail lines have been put into the "tough battle" of the Spring Festival in the Year of the Pig, allowing more passengers to enjoy the comfort and convenience of travel. But when admiring the scenery speeding past the window, many travelers inevitably wonder why most of China's high-speed rail is built on bridges? In this regard, the Economic Daily reporter interviewed Su Wei, chief engineer of the Bridge Institute of China Railway Design Group Co.

At present, most of the high-speed rail lines in the plains of our country are mainly bridge projects. In addition to tunnels, the high-speed rail in mountainous areas is almost all bridges. In my country's first high-speed rail line with a speed of 350 kilometers per hour, bridges account for 88%; in the Beijing-Shanghai high-speed railway, bridges account for 86.5. Su Wei said that high-speed rail bridges can provide safe, smooth and stable lines for trains, thus becoming the key to high-speed rail design.

As one of the basic engineering forms of railway, bridge engineering, its initial function is to make the railway smoothly across rivers, lakes, seas, mountains and valleys, which is also the basic attribute of bridges in a broad sense. For example, China's famous Wuhan Yangtze River Bridge and Nanjing Yangtze River Bridge were built to allow railways to cross the Yangtze River.

After entering the era of high-speed rail, more advantages of bridge engineering are gradually highlighted. "Due to its structural advantages, bridges occupy less land than subgrade projects. Therefore, in the design of high-speed railways in plain areas, we have adopted a large number of bridges instead of common subgrade projects in general-speed railways." Su Wei introduced that land conservation is my country's basic national policy, especially for densely populated and economically developed areas along the high-speed rail, bridges have special significance. According to statistics, "bridge instead of road" can save 43 mu of land per kilometer.

At the same time, because the high-speed operation of the train requires higher line conditions, it usually requires a larger curve radius, which requires crossing with some underground obstacles that cannot be avoided-and the bridge can cross these obstacles and reduce The division of urban space.

In fact, the construction of bridges in high-speed railways is mainly due to technical considerations. High-speed railway has very high requirements on the smoothness of the line, and the line settlement needs to be controlled at the millimeter level. The pile foundation of the bridge is tens of meters deep, or even hundreds of meters deep, which can make the pier "rooted" in the ground, which is more conducive to controlling the settlement and has better adaptability to different geological conditions. At the same time, due to the large number of high-speed rail bridges using concrete structure, material performance is stable, but also reduces the maintenance and repair workload.

"Moreover, most of the high-speed rail bridges are standardized prefabricated in factories and then transported to the site for erection. While ensuring the quality of the construction project is controllable, the construction period is greatly shortened." Su Wei said.