Tunnels

A tunnel is an underground structure to secure roads from the entrance pithead to the exit pithead in mountainous areas. The cross-section of tunnels is significant. At the construction stage, the tunnels were constructed using the technology of that time, penetrating Japan’s complex geological conditions and are currently being used. However, in addition to slope behavior and rainfall-induced topographical changes at the entrance, the tunnel may also experience groundwater fluctuations and changes in the air inside due to geological inhomogeneity. We use our maintenance management technology to address these issues and conduct inspections to ensure safety, comfort and on-time performance, which are the important missions of expressways.

Tunnel inspection work is classified as follows according to the purpose and content required in order to fulfill the important mission of expressways.

Initial inspection
Inspection for the purpose of grasping the initial situation before opening

Daily inspection
Inspection conducted mainly for the purpose of early detection of deformation from the visual and sensations in the vehicle

Periodic inspection
To maintain good conditions over the long term, regular inspections are performed by close visual and tactile inspection and hammering to grasp the state of deformation

Special inspection
Supplements daily inspections and inspections to be carried out in the event of earthquakes, abnormal weather, disasters, or major accidents

Lining concrete
Degradation, peeling/flaking, water leakage cracks and efflorescence

Interior work
Corrosion and damage to mounting brackets and bolts of interior panels, peeling off and damage to tile interiors, etc.

Road surface and drainage system
Uneven road surface and poor drainage facilities

• Investigation and evaluation of cracks in lining concrete
• Proposal for follow-up survey and cause of deformations
• 3D laser measurement inside the tunnels