DESIGN OF VERTICAL ALIGNMENT

VERTICAL ALIGNMENT: 

The vertical alignment of a road consists of gradients(straight lines in a vertical plane) and vertical curves. 

 Gradients: 

Gradient is defined as the rise or fall corresponding to some horizontal distance.

Type of gradients : 

    1.Ruling gradient

    2.Limiting gradient

    3. Exceptional gradient

    4. Minimum gradient

1. RULLING GRADIENTS : 

This is the maximum gradient which is generally used to design the vertical profile of highway. So it is also called as designer gradient. Ruling gradient depends on the terrain, length of the grade, speed, pulling power of the vehicle and the presence of the horizontal curve.

 

2. LIMITING GRADIENTS: 

This gradient is provided as shorter stretches in highways. Whenever ruling gradients costs high for the hilly terrains then limiting gradient is provided which will reduce the cost.

3. EXCEPTIONAL GRADIENTS: 

These are very steeper gradients given at unavoidable situations and they are adopted for stretches not exceeding 100m of length.

4. MINIMUM GRADIENTS: 

To drain of rain water from the road minimum gradient is needed. Generally for lateral drainage Camber is provided. But for the longitudinal drainage along the side drains require some slope for smooth flow of water. 

VERTICAL CURVES: 

THEY ARE OF TWO TYPES_

• Summit curve
• Valley curve

SUMMIT CURVES: 

(I) When upward gradient meets a flat gradient.

(II) When upward gradient meets another upward gradient. 

(III) When upward gradient meets downward gradient. 

(IV) When downward gradient meets another downward gradient. 

VALLEY CURVES : 

(I) When downward gradient meets flat gradients. 

(II) When downward gradient meets upward gradients. 

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