Validating a clear path in advance of the TBM with TISA® 3D

Geological fault zones represent a major challenge in the design and construction of long tunnels. Unstable ground and stable ground with high water table are two ends of the geological spectrum. In addition to unstable ground under high water pressure or mud inrush there are obstructions unknown in advance of the Tunnel Boring Machine or TBM.  Dealing with adverse geology and unforeseen obstructions can lead to significant delays and cost increases in advance of the TBM.  

Inadequate or inaccurate information regarding geological conditions is the most cited reason for almost all projects that have suffered geotechnical difficulties. Minimizing or eliminating this risk requires foresight and advanced planning. It is essential that any tunnel project starts with a comprehensive investigation of ground conditions. Encountering unforeseen ground conditions, objects such as rocks, old foundations or anomalies can be costly in terms of time delays and cost over runs.  

The TISA® 3D Borehole Radar technique continuously gathers detailed information about obstacles and geological transition zones. It is positioned in a horizontal (or vertical) borehole with a diameter of about 20 centimetres, drilled along the planned trajectory. It measures the complete surroundings of the borehole. Rotating 360°, it gathers and processes data from all angles with special proprietary software. After processing, the raw ground penetrating radar data is combined with simultaneously collected positioning data providing meaningful operating data.  

T&A is one of the first geophysical survey companies to successfully integrate radar electronics into a geophysical tool. It is capable of surveying the surrounding soil construction and simultaneously determining the exact position of objects from within one single borehole. Having the complete tunnel track explored in advance by identifying the exact location of objects and obstacles will result in less technical and corresponding financial risks. Providing more relevant information during the drilling process will result in more precise decision making and enhanced safety through the construction process.  

Please contact T&A to learn more about our TISA® 3D Borehole Radar innovative technology and how it might fit with your current suite of engineering tools.