1. CULVERTS1.1. General information Culverts are crossing, serving to lead water from a canal or a drain below a road or another channel. When the height and discharge have been determined, the purpose of the design is to provide more economic sewer, which is that with lower cross section meets the design requirements.The sewers are tubes that can be circular section or frame (square or rectangular) usually buried, used in drains or crosses with roads, can flow filled or partially filled depending on certain factors such as: diameter, length, surface roughness and mainly water, both the input and output levels.In many places, a sewer corresponds to the hydraulic and structural requirements for stream crossing. The adequate structure must be chosen on the basis of the following criteria: The costs of construction and maintenance Risk of failure Risk of damage to property The traffic safety Environmental and aesthetic considerations The convenience of construction.Although the cost of individual sewers tends to be relatively small, the total cost of the sewer with - building constitutes a substantial part of the total cost of the construction of roads. Similarly, the maintenance of the sewer may be responsible for a large part of the total cost of maintenance of the hydraulic characteristics of the road. Improvement of traffic and low cost service can be achieved through a judicious choice of the criteria of design and a careful attention to hydraulic design of each culvert.The sewers are constructed from a variety of materials and are available in many different shapes and configurations. When you select a sewer, the following should be considered: Profiles of roads Characteristics of the channel Assessments of flood damage Construction and maintenance costs Estimates of useful lifeAccording to laboratory research, said that sewer is not submerged if the load on the input is less than a certain critical value called H, whose value varies from 1.2 to 1.5 D D being D diameter or height of the sewer1.2. Types of sewers 1.2.1 types of sewer by the flow at the entrance and exitType I: output dippedFigure 1

Hydraulicload H * entry is greater than the diameter D, and the tie rod at the exit, it is greater than D, in this case the drain is full:Then: H * > D > DD x 1.25 D

Sewer-filled

Type II: output non-submergedFigure 2H > H* Andt