1. Which type of lining is mixed and placed under temperature?
a) Cement Concrete Lining
b) Shotcrete Lining
c) Asphaltic Concrete Lining
d) Dry Stone Lining
Explanation: Asphaltic concrete lining has been under evolution. It is used in very few places. This concrete is a careful mixture of asphalt and graded stone aggregate, and is mixed and applied under elevated temperature. This is a flexible lining and readily confirms to subgrade.
2. What is the biggest advantage of boulder lining?
a) Impervious Lining
b) Dry Stone Lining
c) Dhamalis
d) Pervious Lining
Explanation: As the boulder lining is a pervious lining, it allows free flow of water from submerged or saturated subgrade into the canal. Moreover, this lining does not need any drainage arrangements. This lining can be used in areas where water table is higher than FSL of the canal.
3.Which type of lining is only used for lining the side slopes of the canal?
a) Shotcrete Lining
b) Dry Stone Lining
c) Asphaltic Concrete Lining
d) Cement Concrete Lining
Explanation: This type of lining is only used for lining the side slopes of the canal by proper placing and packing of stones, either after laying a filter paper or not, depending on the soil requirement. Therefore this lining does not help in preventing the seepage losses but helps to maintain the shape of the canal, hence reducing the maintenance cost.
4. Shotcrete lining can be used highly for smaller jobs.
a) True
b) False
Explanation: Shotcrete lining can be used for smaller jobs, because this lining requires lighter equipment and small crew to carry out the works. It can also be used in rehabilitation of old canals and repair works. The trimming of the canal section can be avoided by using this lining in irregular canals.
5. Brick lining gives a very satisfactory service.
a) True
b) False
Explanation: If there is settlement of subgrade in a canal where brick lining is present, the mortar joints present between the bricks or tiles provide numerous cracks so that seepage of canal water would be insignificant. The local area can be repaired without any problem even in case of abnormal settlement.
6. Which type of cement grade is used in cement concrete lining?
a) M20
b) M25
c) M10
d) M15
Explanation: The mixture ratio of M15 grade is 1:2:4 (cement, sand, coarse aggregate) and this ratio is a good quality type for construction of cement concrete lining. This lining gives satisfactory service, high durability, hydraulic efficiency, weed free surface, long life, minimum maintenance cost.
7.For how many days curing of concrete lining takes place?
a) 30 days
b) 28 days
c) 27 days
d) 26 days
Explanation: Curing is mainly done because the concrete which is laid for the lining gains hardened properties over time. After laying the concrete lining a period of 24 to 36 hours gap is given before curing starts. Curing process is done for a period of 28 days. On the canal bed it is done by constructing 150 mm deep earthen bunds across, so that water stands regularly on the bed. On the side slopes it is done by constructing masonry weep holes.
8.In the laying of concrete, what paper is laid to make filter blanket effective?
a) Filter Layer
b) Filter Blanket
c) Tar Paper
d) Sandpaper
Explanation: Before laying the concrete the subgrade should be levelled dressed and moistened thoroughly so that the moisture is not taken from the concrete laid. To avoid this inverted filter blanket is laid over the subgrade before laying the concrete. And to make this blanket effective and to prevent the ingression of concrete being laid on the blanket a tar paper is placed over the filter blanket, before the placing of cement concrete.
9.In soil-cement lining the Portland cement is added to the soil up to the extent of ____________
a) 4% to 5%
b) 2% to 8%
c) 0.1% to 5%
d) > 10%
Explanation: Portland cement up to the extent of 2% to 8% is added to the locally available soil. Water is then added and thoroughly mixed so as to bring the soil to its optimum moisture content. The material is then placed and compacted at the site.
10. Which type of lining is restricted to the availability of suitable soils in the area?
a) Compacted earth lining
b) Soil-cement lining
c) Cement mortar lining
d) Stone lining
Explanation: The use of this lining is restricted to the soil available in the area where the canal has to be constructed. Soil graded to obtain the required characteristics and is compacted at optimum moisture content. Transportation of such soils from outside is not recommended as it would be uneconomical.