This set of Civil Engineering Drawing Questions and Answers for Entrance exams focuses on “Reports on Estimate for the Construction of Road and Irrigation Channel”.
1. The kind of canal section involved in irrigation work is __________
a) canal high in embankment in partly in excavation
b) canal partly in excavation and partly in embankment
c) canal less in embankment
d) canal half in excavation
Explanation: There are generally three kinds of canal sections involved in irrigation works and they are:-
• Canal fully in excavation
• Canal fully in embankment
• Canal partly in excavation and partly in embankment
Generally, the volume of earthwork of earthwork for irrigational canals is calculated by the Trapezoidal formula which is also called End-area formula or the Mid-sectional formula. Generally, the side slope in cutting is kept as 1:1(H:V) and in banking 1.5:1(H:V) or 2:1(H:V) according to soil condition.
2. An impermeable layer is provided at the bed and sides of canal to improve the life and discharge capacity of canal known as______________
a) canal modification
b) canal concreting
c) canal lining
d) canal regulation
Explanation: An important reason for lining a canal can be the reduction in water losses, as water losses in unlined irrigation canals can be high. Canals that carry from 30 to 150 liters/sec can lose 10 to 15% of this flow by seepage and water consumption by weeds. Lining a canal will not completely eliminate these losses, but roughly 60 to 80% of the water that is lost in unlined irrigation canals can be saved by a hard-surface lining. 42 Canal lining Minimizing water losses is very important, and especially so in schemes where irrigation water is pumped. Reduced water losses means less water to pump and thus a reduction in pumping costs.
3. The canal system does not consist ______________
a) main canal
b) branch canal
c) sub-main canal
d) major distributary
Explanation: Main Canal-Main Canal takes off directly from the upstream side of weir head works or dam. Usually no direct cultivation is proposed. Most of the main canals are aligned as contour canals to derive benefit.
Branch Canal-All off takes from main canal with head discharge of 14-15 cumecs and above are termed as branch canals.
Major Distributary-All off takes from main canal or branch canal with head discharge from 0.028 to 15 cumecs are termed as major distributaries.
4. A power canal refers to a canal used for hydraulic power generation, rather than for transport.
Explanation: Nowadays power canals are built almost exclusively as parts of hydroelectric power stations. Parts of the United States, particularly in the Northeast, had enough fast-flowing rivers that water power was the primary means of powering factories (usually textile mills) until after the American Civil War. For example, Lowell, Massachusetts, considered to be “The Cradle of the American Industrial Revolution,” has 6 miles (9.7 km) of canals, built from around 1790 to 1850, that provided water power and a means of transportation for the city. The output of the system is estimated at 10,000 horsepower.
5. Canals are natural-made channels for water conveyance, or to service water transport vehicles.
Explanation: Canals are human-made channels for water conveyance, or to service water transport vehicles. In most cases, the engineered works will have a series of dams and locks that create areas of low speed current flow. These areas are referred to as slack water levels, often just called levels.
An canal is also known as a navigation when it parallels a river and shares part of its waters and drainage basin, and leverages its resources by building dams and locks to increase and lengthen its stretches of slack water levels while staying in its valley.
6. If the total quantity of earth obtained from digging in the bed is equal to the quantity of earth required for the formation of the banks then this is known as economic digging.
Explanation: Also this canal is said to be designed with the balancing depth. Quantity of digging= Quantity in banking i.e. Sectional area of digging=Sectional area of two banks or, Bd+sd2= (b1+b2)*h+2S1 h2 .Although it is never possible to adjust the canal section to this requirement but it may be quite possible in certain portions.
If the quantity of earthwork in the excavation is more than the quantity of earthwork in banking then the surplus earth is thrown away to form spoil bank.
If the quantity of earthwork in the excavation is less than that of banking then the extra earth is taken from borrow pots in the temporary land whose area is calculated for temporary land acquisition.
7. As a modern technique use of plastics in canal lining is that plastic is covered at the top of the canal to prevent dust.
Explanation: The plastic as a material for canal lining offers certain characteristic advantages like negligible weight, easy for handling, spreading and transport, immune to chemical action and speedy construction. The plastic film is spread on the prepared subgrade of the canal. To anchor the membrane on the banks ‘V trenches are provided. The film is then covered with protective soil cover.
8. Laying and consolidation shall be done during dry season.
Explanation: Laying and consolidation shall be done during early rainy season, so that sufficient water is available for consolidation, and during the later part of the rains the ballast gets fully compacted.
9. In water bound macadam roads, binding material is Brick dust.
Explanation: Stone dust is like a darker, coarser version of sand. It is a byproduct of running stones through a crushing machine to make crushed stone. Its exact composition will obviously depend on what kind of stone was run through the machine. For instance, sometimes granite is run through such a machine; in other cases, it could be limestone, for example. The machine has a screen that traps the larger material (that is, the crushed stone). The smaller material or “screenings” falls through the screen. Depending on the size of the holes in the screen used, it can be so fine in texture that it is basically a powder.
10. Chemical admixture may accelerate or slow down the rate at which the concrete hardens.
Explanation: Chemical admixtures are added to achieve varied properties. These ingredients may accelerate or slow down the rate at which the concrete hardens, and impart many other useful properties including increased tensile strength, entrainment of air and water resistance.
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