Side Ditches.

For collecting water from the roadbed side ditches, flumes, interception ditches and drain channeling can be used. Present road construction provides side ditches parallel with the roadway. A side ditch is intended to collect the water discharged by the crown. It also collects the water from the roadside. Water from the

adjoining land must be collected by the side ditch too. The side ditch discharges into a natural outlet at the first opportunity. Side ditches in cuttings and next to embankments may be excavated to a depth of up to 0.6 m. These ditches are for the collection of water flows off the road surface and from adjoining land during rainfall or snow thawing. The side ditch may contribute to the drainage of the sub grade because of the evaporation of moisture from the side ditch inner slopes. However, the major use of the side ditch

is to permit the rapid discharge of water. When this water discharge is not ensured and pending occurs, the side ditch becomes a source from which water may penetrate back under the road, resulting in saturation of the sub grade. The cross-section of the ditch is either V-typed or trapezoidal. In the case of impermeable soils and in less favorable conditions of runoff the side ditches can be given a trapezoidal cross-section with a bottom width of 0.4 m and a depth of up to 0.7-0.8 m from the edge embankment. If the road must be built in dry country with a rapid surface runoff, and the occurrence of ground water is deep, the side ditches are given the shape of triangular flues of 0.3 m minimum depth. The V-typed side ditch can be easily constructed and maintained with the blade grader. The V-typed side ditch cannot be deep and, therefore, it is much safer than the trapezoidal side ditch.

Дата добавления: 2015-07-25