Design methods for drainage of reinforced soil walls

Drainage is an essential feature in the design and construction of reinforced walls and slopes. Cohesive and marginal fills are more and more utilized and the low permeability of these materials requires special attention in the design of the drainage system, both along the perimeter of the reinforced block and inside the fill itself. But even granular soil fills with relatively high permeability may be subject to hydraulic conditions which may cause saturation either at the bottom, at the top, or behind the reinforced soil block, hence requiring again special attention in the design of the drainage system. Various types of draining geocomposites and even a peculiar type of draining geogrids are presently available on the market, in addition to the traditional method of using coarse granular soil as drainage medium. The paper analyzes the different drainage conditions that can be encountered and set the design principles for each case. Then the selection procedure for the suitable draining geosynthetic in each situation is introduced.