Lining, ground and groundwater monitoring underground

Tunnel linings and metro structures carry load from the surrounding soil or rock and from trains and traffic. Instrumentation shows how linings, walls and supports respond, and how groundwater and underground conditions change.

• Tunnel linings: strain, pressure from surrounding soil or rock, and cracking.
• Walls, floors and supports: displacement and tilt of tunnel structures and metro stations.
• Dynamic loads: vibration from trains, traffic and seismic activity.
• Groundwater: flow around the tunnel and possible leakage.
• Underground environment: temperature, humidity, and flow in drainage and ventilation systems.

Laser scanning can record tunnel geometry over time, complementing readings from sensors at specific locations.

• Strain gauges: strain in tunnel linings and metro structures.
• Pressure cells: pressure from surrounding soil or rock on the lining.
• Displacement sensors and tiltmeters: movement and tilting of walls, floors, supports and stations.
• Accelerometers: dynamic loads and vibration from trains, traffic and seismic activity.
• Groundwater flow sensors: groundwater flow and possible leakage around the tunnel.
• Crack and acoustic emission sensors: crack formation and growth in walls and components.
• Temperature and humidity sensors: thermal and moisture conditions underground.
• Flow meters: flow of water, gas or other fluids in drainage or ventilation systems.
• Laser scanning: 3D models of tunnel geometry.