Definition and types of gradients in road
A gradient stands for the expression of slope or inclination in numbers. It is defined as the proportion of distance from a horizontal plane to change of horizontal way of inclination.
If it is assumed that slope or gradient of canal is 1 in 2500 ,it signifies there will be 1 unit fall after 2500 unit distance.
On the road, gradient may come as negative or positive stating fall or rise of the road correspondingly.
Gradient are categorized as follow :-
1. Ruling gradient
2. Limiting gradient
3. Exceptional gradient
4. Minimum gradient
5. Average gradient
6. Floating gradient
1. Ruling gradient: The type of gradient is normally selected at the time of building the road alignment is known as ruling gradient. It is the highest gradient inside which the designer strives to design the vertical profile of a road. It is also called as design gradient.
2. Limiting gradient: This type of gradient is steeper as compared to the ruling gradient. It is effective for a limited Road length. It is described as limiting gradient or maximum gradient. It is suitable when the topography of place requires selecting steeper gradient as compared to ruling gradient to greatly reduce the cost of road construction.
3. Exceptional gradient: This type of gradient is steeper as compared to the limiting gradient. It is perfect to be utilized for short length of road only in extraordinary condition. This type of gradient is chosen only in very complicated situation and for a short length not surpassing 100 m at a stretch.
4. Minimum gradient: The minimum acceptable slope that is ideal for proper drainage of rain water from the road surface is known as minimum gradient. Required minimum gradient in this case is 0.5 % when the side drains are lined and 1 % when the side drains are unlined.
5. Average gradient: It is the proportion of total rise or fall to the horizontal distance among any two points along the alignment of road.
6. Floating gradient: On this type of gradient, a motor vehicle travels with a invariable speed and progresses descend with the similar speed devoid of any application of power brakes is known as floating gradient.
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