Page 172 - RoadCem Manual - PCT BV
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Localised seepage can be corrected in various ways but seepage along pervious layers combined with changes in road elevation (grades) may require subsurface drains as well as ditches, as shown in Figure 6.6. Subsurface drains can be made of geotextiles wrapped around aggregate, with or without pipes installed, but various specialised systems are also marketed. Such drains have commonly been made out of aggregate surrounded by filter sand instead of geotextiles, depending on the grading of the in- situ soils.
As subsurface drainage systems usually incur relatively high installation costs and there is the risk of blocking of buried systems, alternative options are preferred.
Figure 6.6 Beneficial interception of surface runoff and subsurface seepage.
Figure 6.7 Construction of filler in drain.
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