Anticipation, identification of creation of subsidences

Important railway line: Key national 2 tracks line with high rate > 150 trains/day
Over 22 km (14 miles) of non identified sinkholes and weak zones under the track
1 cargo train derailment due to subsidence
Customer ruled out the option of blind drilling and cementation option at cost ~500k$ per 100 linear meters/yards with no guaranty of results, due to the extreme length of the area and unknown positions.

1. Initial Wing nodal survey over 2 x 500 meters (1640 ft) and then fiber optic survey over 3 km (10,000 feet) to identify and cure the zones of danger.
   1. 2 lines of nodal sensors 3 feet apart
   2. 16 hours of monitoring 
   3. 3 hours to deploy, 2 hours to pick up sensors
2. Imaging in 3D with resolution of 1-2 m ( 3-6 ft) with a depth coverage about 1 to 150 m (3-492 ft)
3. Cost effective with minimal human intervention.
4. 3000 m (10000 feet) of Distributed Acoustic Sensing monitoring during 4 hours. Objectives: identify risk zones for confirmation and remediation works

DAS (Distributed Acoustic Sensing) is giving on a long distance a first estimation of potential cavities that will be refined by nodal survey.

Clear identification of risk areas