Why foundation treatment is needed in gravity dam?
FOUNDATION TREATMENT OF THE GRAVITY DAMS. The foundation of the gravity dam should be hard, strong, durable and impervious. The imperviousness of the foundation is very important as uplift pressure depends greatly upon the seepage. Hence to render the foundation water proof or impervious, it has to be suitably treat.
Which dam is more suitable for gravity foundation?
Gravity dams can be classified by plan (shape): Most gravity dams are straight (Grand Coulee Dam). Some masonry and concrete gravity dams have the dam axis curved (Shasta Dam, Cheesman Dam) to add stability through arch action.
What is foundation treatment?
The foundation treatment of Glen Canyon Dam consists of three parts: Grouting, drainage, and excavation of cutoff drifts and backfilling them with concrete. The cutoff drifts and the grouting will seal the cracks and joints. The drainage hole pattern will relieve the water that may seep through the massive sandstone.
Which cement is used in gravity dam?
Low Heat Cement A small quantity of tricalcium aluminate makes the concrete to produce low heat of hydration. Low heat cement suitable for mass concrete construction like gravity dams, as the low heat of hydration, prevents the cracking of concrete due to heat.
What are the main advantages and disadvantages of a concrete gravity dam?
A gravity dam does not fail suddenly. Their failure can be predicted well in advance so that loss of life and property may be saved. Their cost of maintenance is least and benefit of cost ratio is highest. These are found more advantageous in the regions of high rainfall and heavy snowfalls.
What are the disadvantages of gravity dam?
The following are the disadvantages of a gravity dam:
- Their initial cost of construction is high.
- Their construction period is comparatively more.
- These require a strong and sound foundation.
- Dams once constructed, cannot be raised further.
- For the supervision of concrete dams, skilled labor is required.
How do you treat foundation problems?
CONCRETE FOUNDATION REPAIR METHODS
- The two most common methods of this type of repair are slabjacking and hydraulic jacking (also known as piering).
- The most commonly used method of correcting smaller slabs of sunken concrete, such as residential slabs, driveways, sidewalks, swimming pool decks, etc. is slabjacking.
Why do we need temperature control in concrete dams?
If a dam is built under such special climate conditions, specific and strict temperature control and crack prevention measures should be taken. The temperature drop process can be optimized in time, and the temperature drop rate can be controlled to prevent excessive scale and temperature drop rates.
What is GB cement?
General blended (GB) cement produced blending more than 7.5% (as per AS 3972) supplementary cementitious materials. Australian builders GB contains 50% ground granulated blast furnace slag and 50% general purpose cement. GB based concrete or mortar has lower early age strength development and longer setting.
What kind of concrete is used for dams?
The structural concrete used in bridges and dams and other types of road surfaces is made from Portland cement (#). This cement binds the rock (also called aggregate) together to form concrete.
What are the modes of failure in gravity dam?
Modes of failure of a gravity dam:
- Overturning failure.
- Sliding failure.
- Tension failure.
- Crushing failure (or compression failure)
What is the foundation treatment of Glen Canyon Dam?
FOUNDATION TREATMENT 12. GENERAL. The foundation treatment of Glen Canyon Dam consists of three parts: Grouting, drainage, and excavation of cutoff drifts and backfilling them with concrete. The cutoff drifts and the grouting will seal the cracks and joints.
What is the general plan for grouting the rock foundation?
GROUTING. The general plan for grouting the rock foundation beneath the dam provided for low-pressure shallow grouting of the upstream 60 feet of the foundation, to be followed by high-pressure deep curtain grouting from the foundation gallery.
What is the minimum treatment of a foundation?
The minimum treatment of any foundation consists of stripping or removing organic material such as roots and stumps, sod, topsoil, wood, trash, and other unsuitable materials. Cobbles and boulders may also require removal depending on the type of embankment material to be placed.
How deep were the drainage holes in the dam?
The 1 &foot centers and extended into rock approximate1 y drainage holes in the central portion of dam were 85 feet In the lower part of the dam, gradually vertical holes, but fanned out at the ends so that the reducing to 20 feet at the top of the dam. The drainage uppermost holes were free draining.