Underground space, as an essential natural resource of a city, has been applied in number of aspects in developed countries. With the accelerated development of China's economy, the creation and utilization of underground space has received widespread attention. The creation of urban underground construction is becoming more popular. For the underground rail traffic, China first constructed the underground railway in 1965, and so far, many big cities such as Beijing, Shanghai, Tianjin, Guangzhou, Nanjing, Shenzhen, Suzhou, Wuhan and Hangzhou have built part of the subway. China's subway construction has entered into a new stage of rapid development.
How can booming mega-cities be developed into a livable place for billions of people? This question is one of the central, global challenges. The use of measurement technology and sensor technology plays a crucial role in improving the infrastructure in these cities. For example, in the subway construction in the Chinese 6-million-inhabitant city of Nanning: HBK load cells ensure continuous safety in subway construction.