Comoe Dam Lateritic Foundation Treatment: Fid-Bau Portal

Comoe Dam Lateritic Foundation Treatment

Chraibi, A. F. / Nombré, A.

Comoé Dam in Burkina Faso is an embankment dam of 24 m maximum height above the riverbed and around 1170 m crest length. The dam foundations on the abutments are lateritic ground made of a superficial hard duricrust covering a lateritic carapace, soft to firm layer of 6 to 10 m thickness with canaliculus and cavities. The bedrock is made of highly weathered dolerite at the top, sound and watertight at depth. Since the first impoundment of the dam in 1991, uncontrolled seepage appeared at the downstream toe of the embankment on both abutments, particularly on the left bank. Seepage flow gradually increased with time. In 2010, the situation became critical with development of subsidence downstream in the left abutment. Remedial works launched in 2013 included a positive sheet piles cutoff of 40 m maximum depth, tubes-à-manchettes grouting and compaction grouting. Because of the political crisis and economic difficulties, works stopped before completion of compaction grouting and tubes-à-manchettes grouting on the left bank. Although remedial works have not been completed, already a significant reduction in seepage flow and pressures has been observed.