Contractor, Cementation Skanska has negotiated exclusive rights with US designers NSA Engineering for the use and market development in the EU of a pioneering 3D technology system that allows tunnelling ground conditions up to 150m ahead of the face to be viewed on computer.
The technology, called 3D Tomographics (3dT) looks set to reduce tunnel construction risks by alerting projects early to adverse unforeseen conditions. 3dT processes and converts seismic signals into 3D images. These signals can be generated in a number of ways, including the vibrations emitted by a TBM or a rock drill and the reflections picked up on an array of geophones set 20m back from the face.
Before 3dT, traditional geophysical methods of seismic reflection and refraction could only be shown graphically. The 3dT system allows the information to be viewed in three dimensions on computer.
Alun Price Jones, Technical Manager of Cementation Skanska explained to T&TI that its own research showed a gap in ground modelling technology saying’ "This 3D method is streets ahead," he continued, "the holographic image produced (on computer) is essentially a map in 3D of contrasts in the seismic transmission properties of the ground ahead, from which geological features can be interpreted." concluding, "Background signals can be filtered out, so a survey can proceed with the minimum disruption to tunnelling activities. The essential feature for the use of the method is that the nature of the ground ground permitts sound waves to travel through it."
NSA Engineering chose Cementation Skanska as it believed the contractor had the underground experience to show the product in the EU to its full potential.
The system was developed by the US Bureau of Mines, a government body, but research was wound down in 1996. NSA Engineering took on the development launching the product in January 1999. It has so far been successfully used on tunnels in the US, Japan and Austria. Cementation Skanska is actively seeking opportunities to add value to existing and future tunnelling schemes, where the technology can be applied.
