Foundation Grouting at Moulay Youssef Dam

A rational wait-and-see approach to the problem of foundation treatment was developed for Moulay Youssef Dam in Morocco to keep costs down while not decreasing the safety of the structure in any way. This was to carry out a minimum of initial grouting, install piezometers and drains in the foundation, and provide a control tunnel from which problem areas could be identified and given additional treatment after filling if necessary. When Moulay Youssef Dam was filling for the first time, discharge from one of the drains on the right bank increased suddenly giving cause for alarm. Reservoir filling was stopped and further drains were drilled. A wet zone in the control tunnel enabled the suspect area to be localized and heavily grouted, which reduced the seepage to an acceptable level. The main work was done from the control tunnel. Despite the additional works, the final cost was considerably less than the estimate for the traditioonal foundation treatment.