The viaduct is of masonry arch construction with 2 abutments, 17 piers and 18 arches. The viaduct carries the Dublin-Belfast line over the valley of the Camlough River. Abutments, wingwalls and spandrels are of granite block construction. The viaduct has a cumulative span of approximately 450m, 40m at the highest point and 10m wide.
Each span has 12No. designed voids within the body of the superstructure, voids 1-6 are located on the south side of a transverse wall running over each pier and voids 7-12 are located on the north side of the wall.
Scope of works
- Full topographical survey of the viaduct including in-water level survey of the river below
- 3d point cloud survey of external elevations of viaduct.
- 3d point cloud scans of inaccessible, concealed internal voids within the superstructure (5no horizontal cores from elevated platform and 3no vertical cores from track level).
- 360 go-pro video footage of internal void construction.
- Inspection report on the condition of the concealed internal structural elements highlighting defects and confirming as-built dimensions for structural assessment calculations.
- Materials testing to confirm masonry compression strength and shear strength for inclusion in structural assessment calculations.
Innovation
Equilibrant critically appraised available technology to carry out the works. The application of available “off the shelf” technology was not appropriate for the horizontal entry scans. Equilibrant developed a proposal to carry out the 3D scans using techniques which had not been seen previously by the equipment manufacture or any of their approved specialist surveying partners before. Our working mythology included design of bespoke segmental pole and dolly arrangement with a specialist fixing attachment for the scanning equipment and gopro. These were inserted through a 5m long retractable pvc pipe allowing safe and smooth access to the internal voids without damaging/losing the expensive scanning equipment.
To satisfy railway owners Translink, that the information could be gathered using proposed equipment and would be to the high tolerances required by the specification, Equilibrant arranged a mockup trial with Translink in attendance. The trial was carried out in concrete pipes and shipping containers used by a confined space training company to simulate the onsite connectivity issues between the 3d point cloud scanner and control device. It proved that Equilibrants proposed methodology worked.
Equilibrant successfully undertook the scope of work during time critical railway possessions and exceed the project specification as initial cctv surveys were instructed however, the use of 360 go pro footage proposed by Equilibrant produced greater clarity than possible by CCTV thus negated the need.
