What is Canal Lining?
Canal Lining is the impervious layer which protects the bed and sides of the canal. Canal Lining is done to assure economical water distribution, reduction in the possibility of breach, prevent silting of channel and to increase head for power generation. In a lined canal the resistance of flow decreases and velocity of flow increases.
Necessity of Canal Lining :
1. It is done to minimize the seepage looses through bed sides of canal.
2. It is done to prevent scouring and erosion of bed and sides of the canal due to heavy rainfall causing high velocity flood water.
3. It is done to increase the flow velocity, thus discharge in the canal section is increased.
4. It is done to prevent water logging of area which takes place due to rise in water table.
5. It is done to prevent growth of weeds along the bed and sides of canal.
6. It is done to minimize the cost of maintenance.
7. It is done to increase the command area.
Types of Canal Lining :
1. Cement Concrete Lining : Cement Concrete Lining is widely accepted as the best impervious lining. Cement Concrete Lining can resist the effect of scouring and erosion effectively. It can eliminate completely the growth of weeds. The velocity of flow may be kept > 2.5 m/s.
2. Lime Concrete Lining : This lining is less durable than cement concrete lining. However, it can be used where there the plenty of hydraulic lime, surki and brick ballast are available.
3. Pre-cast Concrete Lining : This lining consist of pre cast slabs of 60 x 60 x 5cm which are placed along the side and bed of canal and set with cement mortar. This lining is recommended for the canal with high banking.
4. Cement-mortar Lining : This lining is not durable unless protected suitably. A thickness of 2.5 cm of cement mortar lining can reduce seepage losses by 95%.
5. Brick Lining : This lining is preferred when cost of construction is low and the work needs to be done quickly. It is not completely impervious and has low resistance against erosion, It is recommended to use first class brick.
6. Shotcrete Lining : Shotcrete is the mixture of cement and sand in the ratio 1:4. This lining should be preferred only for repairing works of an old but sound concrete lining. The thickness varies from 2.5 cm to 5 cm.
7. Sodium Carbonate Lining : Since this lining is not durable, therefore it should be preferred very often. This lining consist of 10% clay and 6% sodium carbonate.
8. Asphalt Lining : This lining is done by spraying asphalt at very high temperature (about 120-150 deg C) on the subgrade to a thickness varying from 3mm to 6mm. This lining can control seepage of water effectively but cannot control growth of weeds. This lining is very cheap.
9. Bentonite and Clay Lining : This lining is a mixture of bentonite and clay. It forms an impervious layer over the sub-grade which is effective in controlling the seepage of water, but it cannot control the growth of weeds. This lining is generally recommended for small channels.
10. Soil-Cement Lining : This lining is a mixture of cement and soil in which the quantity of cement is 10% of the weight of dry soil. It forms an impervious layer over sub-grade which is effective in controlling seepage of water but not able to control the growth of weeds. It is highly recommended to use this lining in small channels only.
Tags : canal lining, necessity of canal lining, canal lining definition, types of canal lining.
