Optimization of tunnel excavation methodology and precast segmental lining design for the Devoll Hydropower project, Albania

Abstract

Devoll hydropower project is planned in a southern part of Albania. We focused mostly on optimizing of excavation options, lining design and cost of lining. The chosen alternative for this study is Tomorrice HEP (NC4) among several other alternatives.

We have taken information from previous studies, available data, laboratory investigations, site visits in Albania, meeting and discussing with consultants from Norway, Austria and Germany, access to e-room (online). As most investigations are still pending so not enough data was available, but we have used whatever information was in our access.

From the desk study and geological reports we have tried to establish a overview of ground conditions.Understanding geotechnical conditions leaded us to decide about excavation methods to be used, their efficiency and risks involving ground conditions. Rock mass was found to be poor to fair so rock support measures are suggested accordingly. TBM method was selected as main excavation method and Double shield TBM is recommended.

Lining design is carried out by using the suggestions given by Viglconsult. Lining parameters are recalculated using analytical method. Numerical analysis approach has also been adopted and lining design analysis is done by using FEM program called Phase2 V7.0. The results of both approaches fit together quite well.

Precast lining segment production method and proposed factory are studied. Cost estimation for excavation methods and lining are also discussed briefly.