Pavement Structural Layers.

To ensure all-year-round operation of vehicles traffic on a road, the carriageway is covered with a pavement. The pavement is laid on the surface of the roadbed. It can be rigid or semi-rigid structure. The pavement resists traffic stresses and climatic factors. The stresses induced in the pavement by motor vehicle wheels attenuate with the depth. This enables the pavement to be designed in the form of a multilayer structure. The pavement consists of the following layers: the surfacing, the pavement base, the sub-base and the sub grade. Surfacing is the upper and most rigid layer of the pavement. It is comparatively

thin, but resists well the abrasion and the impacts caused by the wheels, and also the effect of weather conditions. Usually the surfacing is the most expensive part of the pavement. Surfacing usually comprises two coats or courses – a course and a wearing course.

Below the surfacing base coat is the pavement base, a strong bearing layer of stony material or stone with a binding matrix. This layer is designed to distribute the individual wheel-loads over the roadbed or sub-base. The pavement base is not subjected to the direct action of automobile wheels. The sub-base is a layer of earth or stone materials, resistant to moisture, inserted when necessary between the pavement base and the roadbed. The sub-base reduces the required thickness of the pavement base. The sub-base is made of gravel, slag, soil treated with binding agents, sand, etc.

The sub grade comprises the thoroughly compacted upper layers of the roadbed, upon which are laid the layers of the pavement.

Дата добавления: 2015-07-25