Geosynthetics in roads and pavements

 

Typical Solutions 

The traditional approach to subgrade dewatering 

is to dig a trench to the depth to which the water 

table is to be lowered and filling the trench with 

coarse drainage stone.  Sometimes a perforated 

pipe is placed at the base of the trench to more 

efficiently transport collected seepage to an 

outlet.   Trenches are spaced to assure drainage 

of the soil within a desired time period. 

 

Alternatively, in new construction, a coarse 

aggregate drainage layer or “blanket” can be 

constructed beneath and before placing the 

subgrade soil.  Similarly, a pipe system is 

commonly placed within the drainage layer to 

transport collected seepage. 

 

Since groundwater seeping into a drainage layer 

can carry subgrade soil particles with it – a 

phenomenon called “piping”.  To prevent 

piping, a layer of fine sand is commonly used as 

a filter over a drainage layer or in lieu of coarse 

stone in a trench.