Evaluation of The Seepage Conditions in Foundation of the Laúca Dam in Angola Based on Lugeon Tests

Abstract

The watertightness of dam foundations is a critical factor for their safety and performance. This research evaluated the seepage conditions in the foundation and abutment of the Laúca Hydroelectric Project in Angola using water pressure tests (Lugeon Test). The main objective was to determine the permeability of the rock mass and identify the need for grouting treatments. The methodology involved conducting and interpreting Lugeon tests in different boreholes, analysing the flow regime, fracture degree, and fracture infill behaviour. The results indicated significant permeability variability, with Lugeon values (U.L) ranging from 0 (tight) to 400 U.L (very high) in different sections and lithologies. The abutment, composed of metasedimentary rocks, generally showed higher permeability, requiring a more robust grouting program (three or more lines), while the central axis on the gneissic riverbed was predominantly tight or had low permeability, suggesting less intensive intervention. It is concluded that systematic evaluation via Lugeon tests is essential to guide project decisions on the need and design of grout curtains, ensuring the dam's stability and seepage reduction.