The plasticity index (PI) is a measure of the plasticity of a soil. The plasticity index is the size of the range of water contents where the soil exhibits plastic properties. The PI is the difference between the liquid limit and the plastic limit (PI = LL-PL). Soils with a high PI tend to be clay, those with a lower PI tend to be silt, and those with a PI of 0 tend to have little or no silt or clay.

PI is used to relate to that how expansive the clays were. A PI lower than 20 to 24 was generally a safe area...but higher than that and we would then have to respond to swelling clay conditions.

It is a measure of the cohesive qualities of the binder resulting from the clay content. Also, it gives some indication of the amount of swelling and shrinkage that will result in the wetting and drying of that fraction tested. If some soils do not have sufficient mechanical interlock they require amounts of cohesive materials to give a satisfactory performance. A deficiency of clay binder may cause raveling of gravel wearing courses during dry weather and excessive permeability.

To determine Plasticity Index of Soil | Atterberg's Limits

The only difference between a weir and a barrage is of gates, that is the flow in barrage is regulated by gates and that in weirs, by its crest height.

1. Barrages are costlier than weirs.
2. Weirs and barrages are constructed mostly in plain areas The heading up of water is affected by gates put across the river. The crest level in the barrage (top of solid obstruction) is kept at low level.
3. During flood, gates are raised to clear of the high flood level. As a result there is less silting and provide better regulation and control than the weir.

Components of a Barrages | Types of Weirs

The fish ladder:
Fish ladder is provided, for the following purposes

1. For movement of fish (serves as the artificial barrier in either direction)
2. Difference of level on the upstream and downstream sides on the weir is split up into water steps by means of baffle walls constructed across the inclined chute of fish ladder.
3. Velocity in chute must not be more than 3m/s
4. Grooved gate at upstream and downstream - for effective control.
5. Optimum velocity in fish ladder is 6-8 ft/s

Components of a Barrage

Applications of Hydraulics in Practical life

1. Used in Laying out pipes
2. Analyzing rivers
3. Studying Blood pressures
4. Construction of Dams
5. Automatic Transmission machines
6. Water Supply System
7. Sewerage System
8. Flying Planes
9. Brake Oil
10. Hydraulic Jacks

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