Tunnel stability: Verification and documentation

There have been a number of failures resulting in partial collapse in tunnels in recent years, the most recent being in Hanekleiv road tunnel near Sande. Such failures highlight the need for research into tunnel stability and improvement of how tunnel sup port is designed. The consequences of tunnel failures are so important that the profession needs to improve its methods and rethink its practice. The solution lies in finding methods of gaining the required information at the right time, in a cost-effecti ve manner. The proposed research will address the following key elements for tunnel safety: - strategy for improved pre-investigations for tunnel support design, including geophysical techniques, core drilling and borehole mapping - the use of drilling pa rameters from blast holes and/or longer probe drilling holes drilled from the tunnel face to assess rock quality and rock support needs and development of software for data interpretation - methods to verify rock mass quality immediately after blasting by means of fully automated procedures, e.g. photographic scanning, infrared photography, and geophysical techniques (refraction seismics, magnetometric measurements, georadar measurements) - approach for automated documentation of sprayed concrete and rock bolting by scanning, data collection from drilling jumbo, and visualisation by DAK systems - instrumentation and warning systems based on acoustic emission, microseismics and new systems for continuous deformation monitoring based on fibre optic sensor c ables, and verification via a pilot test. The new procedures and technologies developed will form the base for development of new guidelines for practical design and verification of tunnel support systems for drilled and blasted rock tunnels. In light of the tunnel failures that have occurred recently, there is an absolute requirement in this way to involve the entire sector of the tunnelling industry in the improvement of Norwegian tunnelling practi