Remedial Grouting at Mosul Dam, Iraq-PPT Presentation

PPT Presentation

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Mosul Dam, Iraq’s largest dam, is a 3.4-kilometer-long earth dam completed in 1984. Its foundation consists of alternating marl and limestone with soluble gypsum and anhydrite layers. Reservoir water dissolves these layers, creating karst and causing seepage, sinkholes, damaged infrastructure, and unstable monitoring readings. In 2016, a USACE risk assessment identified foundation dissolution as the primary safety concern and classified the dam’s risk as extremely high.<br /><br />From 2016 to 2019, Trevi carried out a major rehabilitation project under USACE engineering supervision. Its main task was to repair the 3.4-kilometer grout curtain through staged pressure grouting, alongside rehabilitation of the bottom outlet tunnels and training for Iraqi Ministry of Water Resources staff. Work was conducted in the dam’s 2.2-kilometer gallery and from the crest and abutments. Crews drilled thousands of boreholes and injected progressively thicker, stable grout mixes at pressures adjusted for depth and geology.<br /><br />An automated system, T-Grout, controlled and recorded the grouting process, including pressure, flow, and grout volume. More than 900 million data points were collected, supporting quality control and analysis of the foundation’s response.<br /><br />The project completed 5,393 boreholes and injected approximately 40,833 cubic meters of grout mix, containing 26,701 tonnes of cement and bentonite. Piezometer measurements confirmed improvements to the grout curtain. A subsequent risk assessment downgraded the dam’s risk substantially; water levels were allowed to rise to those last seen in 2005, and the spillway reopened after 12 years. The project also provided training to 155 Iraqi engineers, technicians, and operators.

Keywords

Mosul Dam

Iraq

grout curtain

pressure grouting

foundation dissolution

karst

seepage

rehabilitation project

T-Grout

USACE