An opening through an embankment for the conveyance of water by mean of pipe or an enclosed channel is called Culvert. It is a actually a transverse and totally enclosed drain under road, railroad, trail, or similar obstruction.
Definition of Culvert
Culvert actually is a tunnel like structure constructed under roadways or railways to provide cross drainage of water or fluid and to take electrical or other cables from one side to other. As per the definition the culvert system is totally enclosed by soil or ground.
It is to be noted here that one similar structure is built where water is taken from one side to the other above the natural ground level that is called aqueduct and should not be confused with culvert.
Typically a culvert can be made from a pipe which can be of PVC or precast concrete sections or reinforced concrete structure. The construction material of culverts can be concrete both reinforced or plain, plastic, steel, Aluminum etc.
The culvert size can vary between few feets to even bigger enough that a person can cross it while standing.
Culverts also come in many sizes and shapes like arch, round, elliptical, flat-battomed, box like shape. Here it is to be noted that the size and shape of the culvert depends on the hydraulic requirements determined by the designer, the amount and quantity of discharge etc.
Type of Culverts
• Pipe Culvert (Single or Multiple)
• Pipe Arch Culvert (Single or Multiple)
• Box Culvert (Single or Multiple Cells)
• Bridge Culvert
• Arch Culvert
Pipe culverts are the least expensive type of culvert and thus are widely used culverts. Pipe culverts are rounded in shape and hence named as pipe culverts. These types of culverts are usually made with steel that is smooth, sometimes a metal having corrugations can also be used, but mostly it is made with concrete. A range of animals of wildlife crosses the obstructions with these pipe culverts as their passageways. Round culverts are best suited to medium and high stream banks.
The culverts may be of single in number or multiple. If single pipe culvert is used then larger diameter culvert is installed. If the width of channel is greater than we will go for multiple pipe culverts. They are suitable for larger flows very well. The diameter of pipe culverts ranges from 1 meter to 6m.
It is a well known fact that circular section is the best geometrical sections for relatively small discharge. Reason is that for a given discharge the area of flow is minimum which makes it most hydraulic efficient structure and it helps save the cost of extra linings required for the choice of box culvert.
Pipe Arch Single or Multiple
Pipe-arch culverts are half-circle shaped culverts that provide low clearance. They may also provide a greater hydraulic advantage to fishes at low flows and require less road fill. Pipe arch culverts are suitable for larger water flows but the flow should be stable. Because of arch shape fishes or sewage in the drainage easily carried to the outlet without stocking at the inlet or bottom of channel. This type of culverts can also be provided in multiple numbers based on the requirement. They are aesthetically very ideal looking culvert.
Box Culvert Single or Multiple
Box Culverts are mostly used in cities and are used to dispose rain water during brief runoff period. Box culverts are in rectangular shape with chamfers at corners and generally constructed by concrete. Box culverts are usually empty in dry season and thus mostly are dry most of the year, this makes it useful for the wildlife to cross the obstruction. Because of sharp corners these are not suitable for larger velocity. Box culverts can also be provided in multiple numbers called cells.
They can have an artificial floor such as concrete. Box culverts generally provide more room for wildlife passage than large pipe culverts. Box culverts are usually made up of Reinforced Concrete (RCC)
If in a pipe arch culvert an artificial floor is provided to the base than we can call it as arch culvert. For narrow passages arch culvert is widely used. The artificial floor is made of concrete and arch also made of concrete. Steel arch culverts are also available but are very expensive. Materials used for arch culverts are RCC, Corrugated Metal or Stone Masonry.