How can engineers control seepage through the foundation under an embankment dam?

To control seepage through the foundation of an embankment dam, engineers employ several countermeasures, often used in combination to ensure the stability of the structure. These methods aim to either block the flow of water or safely manage it to prevent the weakening of downstream components:12

• Grouting: The foundation can be treated with a grout curtain to seal permeable areas.123
• Cutoff Trenches: Excavating a trench and backfilling it with impermeable material creates a physical barrier to seepage.12
• Upstream Blankets: An impermeable blanket can be laid on the upstream side of the dam to extend the seepage path, thereby reducing the flow rate.12
• Drainage Systems: To harmlessly remove water that does seep through, engineers may install a drainage blanket at the base of the downstream section, or utilize individual drainage wells or galleries.12
• Downstream Fill: Placing additional free-draining fill at the downstream toe of the dam helps manage exit gradients and prevent erosion.12

These techniques are essential for maintaining the structural integrity of the dam, especially when it is constructed on unfavorable sites such as open-joined rock or permeable clay.12