China uses 100000 giant screws
Have you ever seen the screws with the thickness of washbasin and the height of four floors? A new high-speed railway in Ningxia is fixed on this screw.
On January 7, science and technology daily came to the construction site of yinwu passenger dedicated line in Ningxia and found that on the compacted foundation, there were concrete discs the size of a dining table. These discs are nuts; There are 20 meters long screws with a diameter of 40 cm, which are buried in the soil. This kind of concrete screw is called "screw pile" by engineers.
"Screws are stronger than nails." Gou yinlao, chief engineer of the project and municipal environmental protection company of China Railway First Bureau, said, "in the same way, threaded pile is more reliable than bare pile. Two thirds of its lower part is screw pattern, which is closely occluded with the soil
This new technology has just been invented, and a small amount of it has been used in construction before. The yinwu high speed railway project is its first large-scale application. The consumption of the whole line exceeds 120000 pieces, and China Railway First Bureau has innovated a series of construction methods for this purpose.
The reason why the high-speed railway is not bumpy is that the track is particularly flat, so the subgrade cannot settle. The support of yinwu high-speed railway is 15-20m long cement pile, which passes through soft soil and is inserted into hard stratum.
The big screw is made like this: the drilling machine turns the screw into the ground, and it turns out for a moment; At the same time, the pipe at the top of the screw ejects concrete and injects the cavity. A cement screw is formed from the bottom up.
The screw pile will compact the foundation soil, and the friction with the foundation is greater. After replacing polished rod pile with threaded pile, the pile density can be reduced by half and the material consumption can be greatly reduced.
"The key is to drill in and out at the same time. If you go down and turn three times to decrease a pitch, you have to turn three times to increase a pitch when you come up, otherwise the newly drilled thread will be damaged." Gou yinlao said, "for this reason, the current of the drilling rig must be very stable, and the power distribution box must be precisely controlled by the computer." The new "screwdrivers" are more than twice as expensive as traditional drills.
At present, Tibet and Ningxia are the only provinces without high-speed rail. The Yinchuan Wuzhong high-speed rail, which connects the two largest cities in Ningxia: Yinchuan and Wuzhong, will be opened to traffic in August. It is also the first ballasted high-speed railway in China. Ballast refers to the track laid on the gravel. Previously, China's high-speed rail was laid on cement slabs. The Beijing Zhangjiakou Railway under construction will be the second ballasted high-speed railway. Ballasted track is easy to adjust settlement and has lower maintenance cost.
In order to ensure the quality, the municipal environmental protection company of China Railway First Bureau has used many new technologies and built the largest Precast Beam Yard in the world. At present, the project has entered the final stage. The main project of high-speed railway was completed in 15 months, creating a speed record of high-speed railway construction.