Uses and Application of a Rockfill Dam

Uses and Application of a Rockfill Dam

Rockfill dam
Rockfill dam. Photo J Rodriguez

Definition: Rockfill dams are embankments of compacted granular soil in combination with impervious areas. Rockfill dams must contain an impervious zone, usually selected aggregates with filter zones, comprising a substantial volume of the dam. These structures are effective because the force of the river or reservoir hits the core of the embankment, in a downward direction, and transferred to the solid foundation of the dam.

If clay is used as impervious material the dam is called a composite dam.

To reduce internal erosion, geosynthetics filters are used to prevent soil migration.Filters are specifically graded soil designed to prevent the migration of fine grain soil particles. Rock-fill dams are resistant to damage from earthquakes. The three main components of a rockfill dam are:

  1. The main rockfill
  2. The impervious zone
  3. Auxiliary supporting members

Rockfill Dam Special Considerations

If you are ever assigned to built a rock-fill dam, pay attention to the following areas:

  • Stability is critical. Both, the foundation and abutment must be stable throughout the life-cycle of the product.
  • Seepage must be controlled to ensure a safe operation Seepage control measures shall be in place before its initial use.
  • The spillway must be strong enough to prevent over-topping of the embankment.
  • Reservoir slopes should be carefully designed

    Advantages of Rockfill Dams

    One of the most important aspects of a rockfill dam is that it can be very economical and cheap to build because materials are most likely to be local. It can also be suited in areas that do not present the best conditions for deep foundations. Another key benefit is that it can be planned in areas susceptible for cold conditions and in hot and humid climates as the rock placement process will not be delayed because of the weather.

    It is an extremely fast process because it does not depends on compaction operations.

    How to Create a Rockfill Dam

    The best way to build a dam is to start by placing the material in controlled lifts.Steel drum roller compactors are used so the material can be locked into place to reduce settlement during subsequent years.  Also these rollers are used to avoid material segregation due to high lift rock fall on the slopes. The dam height can be naturally increased by adding more rocks behind the diaphragm without encroaching the reservoir area. The main rockfill provide the support by its own weight and stability while the membrane holding the water creates and impervious zone. This membrane can also be made out of wood, concrete, steel, asphalt or stone. The dam is then made water-tight by continuing the impervious face upward. Always consult your local building codes and water regulations before proceeding.