ABSTRACT
Tunnelling for large scale pumped hydro or conventional hydropower projects can be a very challenging component of the overall project development. In contrast to urban transportation tunnelling where the logistics for access during the investigation stage and subsequently the supply of power, water and other essentials are readily available for construction, hydropower projects are usually in very remote locations and all necessary plant, equipment, spares, and materials need to be brought in and the site must function as a self-sufficient unit. This differential also applies to the early geotechnical investigations stage.
This paper explores the differences in the typical levels of geotechnical investigation undertaken for two types of tunnel use: firstly, hydropower and pumped hydro tunnels conveying water for power generation and secondly, those for road or rail passenger tunnels. The paper compares some of the technical and risk management considerations in the planning, design, and construction of tunnels for the conveyance of water vs transportation from the viewpoint of different stakeholders to the project.
The risks categories in urban transportation tunnelling projects are similar to those at remote hydropower projects, but the scale of those risks can differ widely. The frequency of drilled subsurface geotechnical investigations is an order of magnitude larger in the urban shallow transportation tunnel project where typical depths below ground are less than 50m, whereas in large scale and remote hydropower the average depth may be several hundred metres.
