At present, the metro construction of our country is at its peak but the security situation is severe since major safety accidents occasionally occur during the construction. Therefore, both the National Science and Technology Plan and Support Programs have listed security control of metro construction as a key research direction. With the support from National Science and Technology Plan and industrial enterprises, the project team has carried out in-depth research. Complete technologies covering the identification, warning and control of security risk have been developed, including security risk automatic identification, coupling warning of temporal risk and spatial risk as well as real-time risk control technology based on the internet of things. Also, the real-time control device for security risk in metro construction has been developed. This achievement won the second prize of National Science & Technology Advancement Awards in 2014. The main innovation points are as follows:

    For pre-construction risk identification, we have created a new method to extract construction risk from engineering drawings with the assistance of computers and have developed the automatic identification system for metro construction security risks, providing scientific evidence for pre-control of security risk and optimization of construction scheme. The technological achievements have been included in the Standard for Construction Safety Assessment of Metro Engineering (GB50715-2011), improving the system for security risk standard of metro engineering in our country.

    For pre-construction risk warning, we have uncovered the spatio-temporal evolution laws of security risk as well as the mechanism of coupling effect and have proposed the warning method for security risk in metro construction, based on information integration and spatio-temporal coupling. This method has been successfully applied to a deep excavation in a subway station project. In this project, the minimum distance from the excavation to the pile foundation of a operating bridge is only 1.25 meters. Using the technology, the traffic over the bridge was not disrupted during excavation.

    For the construction security risk control in complex sections with highly-pressurized confined groundwater, we have invented warning analyzer for metro construction based on the internet of things as well as on-site and real-time control device. This has realized the integration of “detecting, delivering, informing and controlling” of security risk in metro construction under the complex environmental condition with highly-pressurized confined groundwater, ensuring the freezing construction security of the deepest subway connecting passage under water in China. On this basis, we have put forward the method to use liquid nitrogen to rapidly freeze the saturated ground and then carry out slurry-shielded excavation silty and fine sand layer under a water pressure of nearly 400 kPa. This has achieved the safe and rapid barrier clearance as well as shield tunneling machine breakout under river bed, which was the first  in China.

    “The research results of this project have achieved remarkable economic and social benefits and have reached international advanced level as a whole.” In 2009, the results won sci-tech popularization achievements of the Ministry of Housing and Urban-Rural Development. In addition, the achievements have been successfully applied in 9 subway lines in Shenzhen, Wuhan, Shenyang as well as in 158 project departments without major security accidents, strongly supporting the critical engineering construction.