Conventional road
.Conventional road structures
The earliest form of road consisted
of an earth track which had been cleared of vegetation and compacted by human
and animal traffics . Recently , the need for cheap and efficient roads has
resulted in the technical developments of earth road construction in which use
has been made of soil and low grade aggregate .
The road is usually built up in several layers , each having some
special functions. As with modern forms of a road , the construction comprises
of a subgrade layer followed by the construction of a base material layer and laying
of surfacing , as shown in figure (I.7)
The chief function of
surfacing is to provide a wear surface.However the surfacing is sometimes
omitted for cheapness. Very often, on poor subgrade, a sub-base layer of
compacted gravel or stabilized soil is given to distribute the load properly
and prevent the clay working up into the base (22)
