In a rare engineering experience throughout the world, we successfully stabilized relatively coarse materials of drain using

cement grouting. The grouting work was performed at the Karkheh earth dam, southwest Iran, and was part of the efforts to

extend the dam’s cut-off wall. Since the dam was completed, the execution of the new cut-off wall from the dam crest was

inevitable. Hence, one of the main difficulties associated with the development of the new cut-off wall was trenching and execution

of plastic-concrete wall through the relatively coarse materials of drain in the dam body. Due to high permeability of drain, the

work was associated with the possible risk of excessive slurry loss which could result in the collapse of the trench. In order to

achieve an appropriate grouting plan and to determine the mix ratio for the grouting material, a full-scale test platform consisting

of actual drain materials was constructed and underwent various tests. Results of the testing program revealed that a grouting

plan with at least 2 grouting rows and a Water/Cement mix ratio of 1/ (1.5-2) can successfully stabilize the drain materials. After

finalizing the technical characteristics of the grouting work, the method was applied on the drain materials of the Karkheh dam

body. The results were satisfactory and the drain materials were stabilized successfully so that the cut-off wall was executed

without any technical problem.