How are earthfill dams built in compacted layers?

Earthfill dams are constructed by placing soil and rock fragments in thin, individual layers that are then compacted to achieve maximum density. The process relies on the following techniques:1

• Compaction Methods: Finer soils, typically used for the dam's core, may be harrowed before being compacted by rolling. Coarser materials, including rock fragments, are compacted through a combination of vibration and rolling.1
• Optimizing Density: Efficient compaction aims to achieve the maximum dry density of particles with an economic number of passes by the construction plant. This process involves kneading the soil to expel as much air as practicable.1
• Water Content: Achieving maximum strength requires an optimum water content. In arid climates, water is often added to the soil, whereas in temperate climates, the material may require drainage to reduce excess moisture.1
• Structural Design: To ensure stability, the most impervious materials are placed to form a central core, while more permeable substances are placed on the upstream and downstream sides. Filter zones are often inserted between these materials to prevent finer particles from leaching into coarser zones.21