- Tunnel repair with high volume groundwater inflows
- Deepest application of an FRP system for fully-structural tunnel rehabilitation
- Performance of alternative analysis of multiple repair methods
- Limited site access
- Tunnel condition inspection
Faced with groundwater inflow of 300 gallons per minute in this 12-foot diameter water tunnel, MnDOT retained Brierley Associates to develop a solution and effect repairs in a very short time frame in order to limit the flow by-pass duration.
Challenges included high volume groundwater inflow, a limited access point consisting of a 12-ft diameter manhole, and the area in need of repair was a ½ mile distant. Lack of successful grouting challenged the selection of the right technology. The BA team quickly evaluated and selected a proprietary fiber-reinforced polymer (FRP) system (StifPipe®) with a 3D core layer. The StifPipe® system was installed layer by layer and cured in place with increased ambient temperature by using heaters. The repair work was successful and is the deepest application of an FRP system for fully-structural tunnel rehabilitation.