Among the sources of renewable energy, hydropower has continuously gained importance in recent years. New power plants of every size sprout up everywhere and the renovation of many existing schemes is under consideration. Both options require innovative excavation technologies for tunnel, shaft and cavern construction. In addition, the majority of hydropower projects is located in remote mountainous regions or environmentally sensitive areas thus creating challenges with regards to access and logistics.

In general, there are two ways to excavate the tunnels: drill and blast or the use of tunnel boring machines. Compared to conventional Drill & Blast methods mechanized tunnelling solutions have many advantages. Firstly, Shielded Tunnel boring machines offer a high degree of flexibility, they are capable of working through any rock and changing soil, also under water pressure and through "hydraulic soils" at any depth with less emissions to the surroundings. Secondly, particularly for longer tunnels, tunnel boring machines offer increasing cost and time saving benefits. Finally, they allow more reliable project planning and increase the safety onsite.

Today´s mechanized rock tunnelling technologies offer a large variety of solutions for the construction of hydropower schemes. Depending on the expected soil conditions, shielded and non-shielded TBMs can be used. They offer different possibilities of tunnel lining thus guaranteeing safety even in changing or unstable soil conditions. Special adaptations enable inclined tunnelling or blind hole construction, e.g. with retractable machine concepts.

This paper will present different mechanized solutions to install tunnels and penstocks for hydropower schemes. It points out the advantages of tunnelling technologies compared to conventional methods and the challenges such as inclined tunnelling. A selection of case studies will give an idea of potential applications and feasibility in hydropower projects.

1 Introduction

For the development of hydropower schemes, innovative excavation technologies for safe and efficient tunnel, shaft and cavern construction are required. As hydropower plants have to be adapted to the topographical conditions, the placement of the reservoir, size and length of tunnel and penstock structures must follow the given opportunities. As a result, inclined tunnels of different diameters and lengths are needed to fulfil the required parameters to obtain the most efficient power plant operation.

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