Chapter 3: Filters and drains

As an important group of synthetic products, geosynthetics have been widely used in geotechnical engineering practice. In particular, applications of geosynthetics have proved to be successful in preventing water-induced damage of infrastructures or mitigating the negative impacts of wastewater on the environment. Geosynthetics are widely used in transportation infrastructure, including pavements and retaining walls, and facilitate filtration and drainage. Geosynthetics have also been used as filters in stormwater treatment, and in filtering industrial by-products and high-water-content geomaterials, over the past two decades. Several empirical criteria incorporating varying factors of safety are available for the selection of geotextile filters; however, they are, at least in their current form, not directly applicable to high-water-content geomaterials and industrial by-products. An extensive literature review has been undertaken to gather information pertinent to the filtration of natural soils, high-water-content geomaterials and industrial by-products with geotextiles. Factors affecting the behaviour of filtration performance are discussed. The chapter also provides a step-by-step methodology for designing filters and drains.