Advantages and disadvantages of different types of dams: 1. Gravity Dams 2. Earth Fill and Rock Fill Dam 3. Arch Dams 4. Buttress Dams 5. Steel Dams 6. Timber Dams.
1. Gravity Dams:
Advantages:
1. Maintenance cost is negligible.
2. They are specially suitable for deep steep valley conditions where no other dam is possible.
3. If suitable foundation is available, such dams can be constructed for very large heights.
4. Because they can be constructed in very large heights, they can store more amount of water.
5. If suitable separate place is not available for installation of spillways, they can be installed in the dam section itself.
6. This dam gives prior indication of instability. If remedial measures are taken in time, unsafe dams may even be rendered safe. Even if they cannot be made sale they give sufficient time for the people to move out the area likely to be submerged due to failure of the dam.
7. Silting rate of the reservoir can be reduced considerably by installing under sluices in the dam near the bed of the reservoir. Sluices can be operated from time to time and silt may be scoured out of the reservoir.
8. They are not affected by very heavy rainfall. Earth dams cannot sustain very heavy rainfall because of heavy erosions.
Disadvantages:
1. They are very costly in initial construction.
2. They take lot of time of construct.
3. They require skilled labour for construction.
4. Such dams can be constructed only on good foundation.
5. If height of the dam is to be raised, it cannot be done unless provision for it had been made in the construction of the lower part of the dam.
2. Earth Fill and Rock Fill Dam:
Advantages:
1. They can be constructed on any type of foundation
2. They can be constructed in comparatively less time.
3. They do not require skilled labour.
4. Initial cost of construction is low as locally available soils, and rock boulders are normally used.
5. Their height can be increased without any difficulty.
6. They are specially suitable for conditions where slopes of river banks are very flat. Gravity dams under such conditions are not found suitable.
Disadvantages:
1. They fail all of the sudden without giving any pre-warning.
2. Flood waters affect the dam safety.
3. Spillway has to be located independent of the dam.
4. They cannot be constructed as overflow dams.
5. They require continuous maintenance.
6. They cannot be constructed in narrow steep valleys.
7. They cannot withstand heavy rains unless properly protected.
8. They cannot be constructed in large heights. The usual height is 30 m for which most of the earthen dams are constructed.
3. Arch Dams:
Advantages:
i. They are particularly suitable for narrow deep gorges. In such conditions arch dams prove even more suitable than gravity dams.
ii. They require comparatively very small amount of construction material. The section or thickness of the dam is very small in comparison to the gravity dam.
iii. Uplift pressure is not very large as base width of the dam is quite small.
iv. They can be constructed on moderate foundations.
Disadvantages:
i. They require very complicated form work which is very costly.
ii. They require very skilled labour.
iii. Design of the dam is also difficult.
iv. Speed of construction is very slow.
v. They require very strong solid rocky abutments to resist the thrust of the arch.
4. Buttress Dams:
Advantages:
1. They can be constructed on weak foundation because they are less massive than gravity dams.
2. The load of water lying on the inclined deck slab adds to the vertical component, of the dam and as such helps in increasing the stability of the dam. The factor of safety in case of buttress dams is far greater than for gravity dams.
3. Since ice tends to slide over the inclined U/S surface, ice pressure does not carry any significance.
4. Height of buttress dams can be increased by extending both buttresses and deck slab.
5. Power houses or other plants can be located in the empty space between buttresses.
6. They require only half to one-third amount of cement concrete in relation to the concrete required for gravity dam for the same height. The cost is not reduced by the same proportions as increased cost is required for form work and reinforcement.
7. Because of space between buttresses, it is possible to reach the back space of deck slab. By reaching here periodic inspection of foundations etc. can be carried out.
8. Since exposed surface of concrete is more but volume of concrete is less than the gravity dam, heat dissipation during construction is achieved better. Also speed of construction can be increased as thinner sections do not cause any problem for cooling.
Disadvantages:
1. More skilled labour is required.
2. Shuttering cost is more.
3. The slab being very thin, its face in contact with water is likely to deteriorate and cause damage to the dam.
4. It is more susceptible to deliberated damage. It is so because thickness of slab is very small and also there is approach to reach back of the slab through the space between buttresses.
5. Steel Dams:
Advantages:
1. They are cheaper than other rigid dams.
2. They can be built in very short time with modern methods of fabrication.
3. They are more adaptable in case of unequal settlement of foundation.
4. They are more leak proof.
5. Frost action does not have any adverse effect on steel.
6. They can be repaired easily by welding.
Disadvantages:
1. Life is shorter than concrete or masonry dam.
2. They require constant maintenance.
3. They are not as adaptable to vibrations due to spilling water. This is because they are too light.
4. They have to be anchored with foundation.
5. Bearing stresses are excessive as bearing are in this case is very small.
6. Timber Dams:
Advantages:
1. Initial cost is low.
2. Can be erected in very short time.
3. Can be constructed on any foundation.
4. Very much used for temporary works.
Disadvantages:
1. Have very small life.
2. Suitable for very small heights.
3. Maintenance cost is high.