Post-tensioning is a method of reinforcing concrete, used extensively in the construction of buildings and bridges.
High-strength steel tendons are positioned in ducts before the concrete is poured. Once the concrete has gained strength, tension is then applied, pulling the tendons and anchoring them against the outer edges of the concrete, before service loads are applied.
When drilling into a concrete slab for the purpose of installing machinery, office furniture, pipework, air conditioning etc., there is always a risk that a post tension steel cable may be accidentally cut or damaged. This can weaken the slab structurally or the cable (which is under tremendous pressure) may rip out of the slab, causing severe injury to anyone in the vicinity. The cost to repair a single post tension cable alone is £1000+ and it can affect the entire stability of the building.
SUMO uses non-destructive and non-invasive high-frequency Ground Penetrating Radar (GPR) to locate the position and depth of post tension cables.
Above left : 2GHz GPR Antenna with SIR 4000 controller. Above right : Example Radargram. Reinforcing bars and post tension cable.
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The above images show the data in section view to a depth of c. 300mm. The post tension cables are clearly visible below the reinforced concrete. These section views can either be interpreted and marked up on site, enabling the location of the cables to be clearly identified to the contractor in situ, or recorded and interpreted back in the office, where a drawing is produced and a permanent record established. A basic report can also be made, showing photos of the identified post tensions cables and their location within the survey area, as shown below.
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Area A
Area B
Above : Basic report showing photos of post tension cables and their location.
Geophysical Engineering Surveys
Air Raid Shelters
Cellars & Basements
Post Tension Cables
Underground Storage Tanks
Air Voids
Chimney Flues
Rebar
Water Engineering
Badger Setts
Earthing Installations
Sinkholes
Burials
Geological Application
Soil Thermal Resistivity Testing
Buried Foundations
Landfills
Structural Investigations
Buried Manholes
Mineshafts
