ENGINEERING GEOLOGY IN DAM CONSTRUCTION

ENGINEERING GEOLOGY IN DAM CONSTRUCTION

Introduction:

• Geological considerations play a vital role in location of Dams & Reservoir.
• Type of dam is based on valley characteristics & Geology.
• Foundation requirements also depend on the type of the dam.
• Dams intended for more than one purpose are called “Multi-purpose dams”

Dams are constructed for:

1. Generation of hydroelectricity,
2. Irrigation,
3. Flood control,
4. water storage or supply and
5. Regulating & control of stream load.

 Most of the dams in India (90%) are operating for irrigation only.

TYPES OF DAMS

GRAVITY DAM:

• These are heavy concrete dams.
•  Stability is secured by making it of such a size and shape that it will resist overturning, sliding and crushing at the toe.

ARCH DAM:

• In Arch dam, stability is obtained by a combination of arch and gravity action.
• Firm reliable supports at the abutments (either buttress or canyon side wall) are more important.
• The most desirable place for an arch dam is a narrow canyon with steep side walls composed of sound rock.

Buttress dam:

• Buttress dam is a water-tight dam supported at intervals on the downstream side by a series of buttresses or supports.
• The dam wall may be flat or curved.
• A buttress dam is a good choice in wide valleys where solid rock is rare.

EARTH DAM:

• Constructed with earth materials.
• This is large in size and Trapezoidal in shape.
• Earth materials used in construction are gravel, sand, silt and clay.
• Filters are provided to facilitate drainage and also to release pore-pressure.

Location of a dam: (Ideal site)

1. Narrow valley with steeper side slopes.
2. Stable slopes .
3. Absence of weathered formations, clay and fractured material .
4. Absence of weak zones .
5. Reservoir should be water tight .
6. Easy access and supply of materials for construction site .