Short Answer:

Types of curves used in surveying are mainly used to provide smooth transitions between two straight paths, such as in roads, railways, and canals. These curves help avoid sharp turns, ensure safety, and maintain alignment. The curves are classified based on their shape and application.

The main types of curves include simple circular curves, compound curves, reverse curves, and transition curves. Each type has a specific purpose and is used depending on the terrain, design requirements, and nature of the project.

Detailed Explanation:

Types of curves used in surveying

Curves in surveying are designed paths that help in changing the direction of a route smoothly and safely. They are an essential part of civil engineering projects like highways, railways, and pipelines. These curves are placed between two straight paths to avoid sudden changes in direction, which could cause discomfort, danger, or structural failure.

Different types of curves are used based on the specific needs of the project and site conditions. Proper selection and setting out of these curves is vital for ensuring comfort, safety, and design accuracy.

1. Simple Circular Curve

A simple circular curve has a constant radius.
It is the most commonly used curve in field surveying.
It is used to connect two straight lines (tangents) with a single, smooth curve.
Easy to set out using deflection angle or chord methods.
Applications: Roads and railway turns.

2. Compound Curve

It is made up of two or more simple curves with different radii but lying in the same direction.
Used when the change in direction is large, and a single radius curve cannot fit properly.
Provides a smoother transition than a simple curve in sharp bends.
Commonly used in mountain roads and railways.

3. Reverse Curve

Consists of two simple curves bending in opposite directions, connected at a common tangent point.
Also known as S-curve.
Useful where space is limited and direction needs to be corrected quickly.
Not preferred for high-speed roads due to sudden change in direction.

4. Transition Curve

The radius of the curve changes gradually from infinity to a designed value.
It provides a smooth entry and exit from the curve.
Used in highways and railways to reduce shock and provide comfort during turning.
Types include spiral, clothoid, and cubic parabola.

5. Vertical Curve (in profile view)

These are used in the vertical plane to connect two different slopes.
Used in road and railway construction to ensure smooth upward or downward slopes.
Types: Summit curve (convex) and valley curve (concave).

Conclusion

Different types of curves in surveying are chosen based on how smooth and safe the change in direction needs to be. Simple, compound, reverse, transition, and vertical curves each have unique properties and uses. Surveyors must understand these types to apply the correct curve in a project, ensuring smooth movement and structural stability.