Geophysics for Tunnelling

Most of the time, while working on tunnels, caverns and other underground projects, decision makers are working with limited and imperfect information. Engineering geophysics is an efficient means of subsurface investigation to fill in the information gaps and provide a complimentary source of information to enhance our understanding of subsurface conditions. The merit of application of this low cost aid lies in its ease of deployment and rapidity in providing a reliable knowledge of the underground over a large area, substantiating the requisite geotechnical evaluation studies thereby. Technological advancements and development of portable digital data acquisition instrument systems have increased the versatility in evaluating underground conditions and site characterization. The state-of-the-art subsurface geophysical investigations are helpful towards minimizing & optimizing involvement of the conventional direct exploration methods, aiding in accelerated and economical development of the underground construction projects. The investigations also play a key role in quality checks of construction and non-destructive health checks during entire life cycle of tunnels, caverns and other underground projects.

PARSAN provides comprehensive solutions for tunnel route studies:

1. Airborne Geophysics (in collaboration with SkyTEM and NGI)
2. Seismic Refraction
3. Electrical Resistivity Imaging
4. ReMi/ MASW
5. Seismic Tomography

A paper titled 'Advancement in Geophysical Investigations for Tunnels' can be downloaded by clicking here.

Real-time prediction during TBM advance through the BEAM system

The Bore Tunnelling Electrical Ahead Monitoring (BEAM) system, developed by the GET Company, Germany, is a geophysical ground prediction technique especially designed for TBM operations. BEAM is a non-intrusive focused-electrical induced polarization ground prediction technique, permanently operating while TBM advances. The intent is to get a continuous real-time geological forecast ahead of TBMs, useful to predict the quality of the groundmass and the presence of large quantities of water. The system has proven to be very reliable in providing an accurate forecast of the different hydrogeological parameters of the formations in front of the TBM and of the expected TBM performances and criticalities. The BEAM system’s predictions have been reliable in various projects in almost 80-92% of the cases: they allowed to be prepared to the geology ahead of the TBM and to better plan the TBMs operation and maintenance. The system minimizes the geological surprising while tunneling and gives valuable information to prepare for geology to be encountered.

A short note on the technology can be downloaded by clicking here.

GPR survey of Tunnel Face

Ground penetrating radar surveys conducted from tunnel face can also provide invaluable information of formation ahead, indicating presence of water bearing zones, fracture zones etc.

PARSAN specializes in GPR surveys from tunnel face.