Canal lining is provided to prevent the seepage losses of water. Canal lining can be constructed using a variety of materials. There are some factors to be considered while selecting good canal lining material and those factors are discussed briefly in this article.
Factors Affecting Selection of Good Canal Lining
Following are the factors affecting selection of canal lining :
- Erosion resistance
- Hydraulic efficiency
The lining selected for a particular canal should be economical. The economy of canal lining project generally depends upon many factors such as the type of material used for construction, availability of materials, availability, construction equipment, the period of construction etc. A canal lining is said to be economical when the repair and maintenance costs are inexpensive along with the initial construction cost.
The canal lining should be durable in such a way that it should survive in peak flow conditions, canal empty condition, all weather conditions, against temperature changes, chemical actions etc. The lining should be inspected periodically to prevent the growth of rodents, weed, etc. which affects the durability of the structure.
The maintenance of good canal lining is always easy and economical. A canal lining constructed using bricks or concrete tiles or stone boulders can be easily repaired. Cast in situ concrete lining is difficult to repair when it is damaged. But however, cast in situ concrete lining requires less maintenance than others because of its structural stability.
There are various pressures that act on a canal lining. Soil behind the lining may get saturated due to rainwater or seepage and exerts severe pressure on the lining. Sometimes cavities can form behind the lining and create problems. The canal lining should survive against these type of pressures. So, the lining provided should be heavy, strong and stable.
5. Erosion resistance
The canal lining material should have good resistance against erosion. Erosion occurs due to abrasion of sediments present in the water with canal lining surface. If the canal water contains sediments in a considerable amount, then concrete lining or stone boulder lining is preferred since they are good in erosion resistance.
The main reason behind the provision of lining for the canal is to protect the water from seepage losses. Hence, the canal lining should be efficiently impermeable. However, some types of linings like compacted earth lining, soil cement lining are provided to reduce the seepage losses up to a limit.
Concrete lining, plastic lining etc. are more impermeable but uneconomical. The type of lining with respect to seepage losses is selected based on different factors such as percentage of seepage, water demand, population intensity etc.
7. Hydraulic efficiency
The hydraulic efficiency of the canal gradually decreases with time. When the lining surface is continuously exposed to water flow, the surface becomes rough and erosion occurs which reduces the hydraulic efficiency of a .