In excavated areas and cuttings where the longitudinal slope is more than 3%, a longitudinal water flow may appear fed by water from under the pavement that is
|
Water*………………. ……………….. table with drain ^ | |
separate from the flow in channels, gutters and gully’s. In these cases, the inclusion of pavement underdrains (Fig. 13.26), installed transversally under the pavement, can be used, in order to collect all subsurface waters. These kinds of drain are best constructed in transition areas and, in areas of excavation or fill, placed centrally to improve the rapid flow of the infiltrated water. In sandy soils they should be placed with a spacing between 20 and 25 m while, in very clayey soil, these distances should be reduced to about 5 m.
It is advisable that these transverse drains be constructed in a trench, filled with drainage material wrapped in geotextile, or by synthetic filters, constructed right
down below the level to be drained. In cold regions, the dimensions and depth of the network may be greater than in non-frost affected regions.
