What is flexible pavement in highway engineering

➤ Flexible pavements: These are the pavements which have very less flexural strength. They transfer the load coming over them directly to the lower layers through grain to grain contact. So the load transfer largely depends upon the type of the grains/aggregates that are used in the construction of the pavement.  If the aggregates are well compact/ well graded then their grain to grain contact will be good and they can transfer the load to a wider area. The flexible pavement has the following layers:
(a) Wearing course
(b) Sub base course
(c) Base course
(d) Sub grade
The stress intensity is maximum at the top layer of the pavement and it decreases with depth. Due to ability of the pavement to transfer the loads to lower layers in the truncated form, the layer concept has been introduced for its construction. The pavements is made of layers of different materials. The top layer is made of superior material, because it has to face the largest stresses, and the lower layers are constructed with with inferior materials.  So the wearing course is made of the superior quality material and sub-grade can be constructed of the locally available earth too. The materials like bituminous concrete, is best to use as the surface course and the others like water bound macadam, and other crushed aggregates, gravels can be used for the base and sub base courses. The flexible pavements are designed with the help of the empirical design charts or some equations taking into account the various design factors. Some semi-empirical and theory methods are also available for the design of the flexible pavements.
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