Carrak Consulting Ltd is pleased to be working with EGS Energy Ltd on a project to assess the condition of abandoned mine shafts in Cornwall. The project is funded by Deep Digital Cornwall and will trial novel techniques to survey open shafts remotely, avoiding health and safety risks to personnel.
The shafts have been selected based on their connection with strategic flooded workings and to provide information to further the aims of the Southwest Geothermal Alliance in developing a mine water geothermal scheme in Cornwall.
Mine shafts were located by Carrak Consulting Ltd and visited by researchers from Camborne School of Mines (University of Exeter) to assess suitability for the survey technology. The first survey was carried out this month on an over 200 metre-deep shaft using a steel gimble-mounted ‘Revo’ laser scanner. The Revo laser scanner needs to be stationary for 15 seconds with a good view of geometry before surveying starts. The scanner was held centrally in the shaft mouth using a series of ropes and pulleys and returned to surface in between data captures so that the scan could close its Simultaneous Location And Mapping (SLAM) loop.
Cloud based ‘GeoSlam’ processing software was used by Camborne School of Mines to render and stitch the scans. Data polishing and integration was carried out in CloudCompare and Meshlab software. Some 3D trajectories down the shaft were modelled to show how the data could aid engineering design decisions, like the placement of pumping pipework and values.
Models of the shaft interior clearly showed the condition of the collar, profile of the shaft walls and a connecting drive (tunnel). The resolution was good enough to show any spalling as well as existing timbers or any other infrastructure left in the shaft prior to abandonment. The use of sonar to survey below water level is now being explored.