Culvert: types, dimensions, device

For drainage of small water drains and their passage under the road, culvert is used. Their use is more appropriate than the construction of a bridge.

General concept

To pass water from the upper part of the motor roads to the lower one, culverts are used. These include culverts, bridges, drainage. The latter are used to pass under the roadbed of various channels.

Culvert is used in cases where it is necessary to pass small drainages under the road (streams, draining water after rain or melting snow, etc.). The water passage through the pipes can be carried out continuously or periodically. Through such structures sometimes organize the passage of cattle or the passage of transport.

The design of culverts does not require a narrowing of the roadway and a change in the type of road surface. Backfilling is done on the structure. The thickness of the layer of excavated soil reduces the pressure on the structure from the cars and softens their influence.

The use of water pipes has its advantages:

• Installation of pipes passes without damage to the roadbed.

• Installation of pipes is cheaper than building a bridge.

• At a thickness of a bed of a filling more than 2 m influence on a construction of time loads from passing transport is reduced to a minimum.

Pipe sizes

The diameter of the culvert depends on its length:

• If the length of the pipe does not exceed 2-3 m and the height of the embankment is less than 7.5 m, then the pipe hole is chosen equal to 100-150 cm.

• For a mound up to 1.5 m, the diameter should be 75 cm.

• Pipes within the limits of the congresses are 50 cm in diameter.

Under the roads of 2-4 categories, it is allowed to use culverts with a diameter of 100 cm and a length of up to 30 m. If the diameter is 75 cm, then the pipe length should not be more than 15 m.

Classification

Culvert is classified according to several parameters.

Depending on the material from which they are made:

• Concrete.

• Polymer (from polymer concrete, polyvinylchloride and polyethylene).

• Reinforced concrete.

• Stone.

• Metal.

• Fiberglass.

There are several types of pipes, depending on the shape of the cross-section:

• Round.

• Arched.

• Elliptical.

• Rectangular.

• Trapezoidal.

• Ovoid.

• Triangular.

By the principle of operation of the section:

• Non-pressure.

• Pressure head.

• Semi-pressure.

In the cross-section of the pipes there can be one, two or several glasses.

Basic elements of the pipe and their installation

Culvert consists of several elements:

• Entrance headline.

• Tube links.

• Output headline.

Due to the presence of the heads in the pipe there are no whirlpools, swirls, the water flows more slowly. Their presence does not allow flowing water to blur the mound and wash away the foundation.

There are several types of headings:

• Portal, which are constructed in the form of a perpendicular wall to the retaining wall. This is the simplest design, but it has its drawbacks. It does not ensure the smooth flow of water. Therefore, its use is recommended in cases with a small amount of water flowing at low speed. Portal headers are used for pipes with a diameter of 50-75 cm.
• Spigot. In addition to the wall, they have two openings forming a bell. The flaps are located at an angle of 30 degrees to the pipe. Due to this, the water flow gradually narrows.
• Collar, in which the extreme element is cut at the same angle as the mound. A protective collar is installed along the contour.
• Streamlined in the section gradually narrow, which creates good conditions for the flow of water.

The ground pressure is distributed evenly by the foundation on which the pipe is laid. This also prevents the displacement of individual elements of the structure.

There are the following types of foundation:

• Without foundation (natural foundation).

• Ground cushion created artificially.

• From monolithic concrete.

• Of individual reinforced concrete elements.

The choice of the type of foundation depends on the diameter of the pipe, the height of the embankment and the geological conditions.

Culvert is located strictly perpendicular to the axis of the road. This gives the minimum pipe length. In some cases, it is recommended to install the structure in the direction in which the flow is flowing. This reduces the likelihood of a whirlpool. In such cases construction of culverts in other directions is allowed.