Design criteria and main features of the underground works for Las Placetas, Dominican Republic

This paper presents the main features of the underground works for Las Placetas, a 204 MW hydropower project in the Dominican Republic, owned by state company EGEHID and currently being planned by the consortium of Andrade Gutiérrez-OCECON. The project will feature two underground powerhouses with installed capacities of 152 MW and 52 MW, as well as more than 30 km of underground works, including a mechanically excavated 6.5 km tunnel utilizing a double shield TBM. The region where the tunnel is located presents heterogenous geological formations and variable rock cover conditions, imposing geotechnical design challenges. This paper provides an overview of the scheme’s geological-geotechnical background, and shares the analytical, empirical-observational and numeric methods used to define the project’s main features, as well as primary support treatments for drill and blast excavated tunnels and caverns. It also highlights the role of primary support in concrete lined tunnels.