Urban Lifeline Safety Engineering Application
Seismic waves are the beacon that illuminates the underground space.
Urban Geological Structure Monitoring
- Using the HiFi-DAS distributed optical fiber acoustic sensing system to image urban underground spaces is like performing a CT scan of the city. Based on seismic wave signals generated by traffic activities, new seismic interferometry techniques and weak signal extraction methods are employed to replace active sources for shallow subsurface imaging, enabling detection and early warning of roadbed stability, tunnel structures, underground cavities, underground rivers, and leakage.
Figure1：Blue indicates harder rock and soil, while red represents softer rock and soil.
- The main cause of urban road collapse is underground cavities. The HiFi-DAS high-precision distributed fiber optic acoustic sensing system can detect cavities as small as 0.8m x 2m, providing 24-hour real-time monitoring. It uses imaging technology to display underground cavity changes in real-time and provides early warning for potential collapse risks.
Figure2：Through long-term monitoring of cavities, changes in the cavities can be detected.
Intrusion Detection and Early Warning System for Urban Underground Communication Optical Cables, Water Supply Pipelines, Heating Pipelines, Gas Pipelines, and Power Pipelines
Figure3：Acoustic waves for detecting various third-party intrusion events
Structural safety monitoring and leakage detection for urban water supply pipelines and gas pipelines
The outstanding advantages of using distributed optical fiber acoustic sensing system for pipeline leakage monitoring:
- Low detection cost and energy consumption.
The number of hardware components used in distributed optical fiber acoustic sensing systems is significantly lower than other traditional distributed pipeline leakage detection systems.
- Good environmental adaptability.
Buried water and gas pipelines have long distances and wide geographical spans, with significant differences in the natural environment around the pipelines. Optical fiber is a quartz insulating material that is corrosion-resistant, high-temperature resistant, radiation-resistant, and explosion-proof, without the need to consider discrete current interference. It has advantages that electrical sensors cannot match, making it very suitable for urban gas pipeline networks in flammable, explosive, and strong electromagnetic interference scenarios.
- Simple and convenient installation.
Optical fiber is lightweight, flexible, and has a diameter of about 900µm (excluding protective layer), which can meet the requirements of complex natural gas pipeline networks. It enables large-scale, long-distance, and global detection networks.
- High safety.
Using optical fiber as the carrier of leakage signals ensures that even if buried natural gas leaks, there will be no electrical sparking, avoiding secondary accidents.
Urban Road and Bridge Structural Health Monitoring
By monitoring the first vertical bending frequency changes of bridge structures within the city, the health status of bridge structures can be determined. If the first vertical bending frequency exceeds a certain threshold, it indicates that there is a problem with the bridge. The figure below shows that the first modal vertical bending frequency of a certain bridge is around 3.88Hz, and it has remained unchanged since the system was deployed.
