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Which is the most preferred shape of drainage?
Rectangular
Trapezoidal
Triangular
Circular
Trapezoidal
The trapezoidal shape is preferred for drainage because it is structurally stable, easy to construct, and provides a balance between hydraulic efficiency and excavation economy. Its side slopes allow for the use of lining materials and reduce the risk of side wall collapse compared to vertical or rectangular sections.
The trapezoidal shape is preferred for drainage because it is structurally stable, easy to construct, and provides a balance between hydraulic efficiency and excavation economy. Its side slopes allow for the use of lining materials and reduce the risk of side wall collapse compared to vertical or rectangular sections.
A=(b+nh)h тАФ Area of trapezoidal section where b is bed width, n is side slope, h is depth
P=b+2h1+n2тАЛ тАФ Wetted perimeter of trapezoidal section
R=PAтАЛ тАФ Hydraulic mean depth
The design of a drainage section involves maximizing the hydraulic mean depth (R=PAтАЛ) while minimizing the wetted perimeter (P) to increase flow velocity. Trapezoidal sections accommodate varying flow rates more effectively than rectangular ones and are significantly more stable in earthen embankments because the side slopes match the natural angle of repose of the soil.
Trapezoidal sections are standard for large drains and open channels.
The side slope (1:n) is chosen based on soil stability.
Easier to maintain and clean compared to circular pipes for large flow capacities.
Provides a wide top width which helps in managing surface runoff during heavy rain.
Greater structural stability in earthen cuts
Easy to line with concrete or stone masonry
Higher capacity to handle peak discharge
Requires more land width compared to circular or rectangular drains
Higher evaporation loss due to large surface area
Highway and roadside drainage
Irrigation canals
Stormwater management in urban areas
| Feature | Rectangular | Trapezoidal |
|---|---|---|
Efficiency | Moderate | High (Best for soil) |
Construction | Simple (Vertical walls) | Simple (Sloped walls) |
Circular pipes are preferred for sewers where flow is pressurized or needs to be closed.
Rectangular sections are often used in restricted spaces or urban roadside gutters where land width is limited.
B is correct тАФ The trapezoidal shape is the most preferred for drainage systems due to its superior stability and hydraulic efficiency in open channel flow.
In competitive exams, remember that for 'most efficient' hydraulic sections, the semicircular shape is best, but for 'most preferred' in general drainage practice, trapezoidal is the answer due to construction feasibility.
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