Tunnel health monitoring uses sensors (like fiber optics, strain gauges, LiDAR, tiltmeters) and data analysis to continuously track a tunnel's structural integrity, safety, and performance, detecting issues like cracks, deformation, water ingress, and stress changes to enable timely maintenance, ensure longevity, and prevent failures during construction and operation. It involves collecting real-time data on displacement, strain, temperature, and load, allowing engineers to assess stability and manage assets effectively.