Geotextile materials permeability

FML placed on a bed of sand, geotextiles, or other highly permeable materials would allow liquid to move through the defect in the FML, spread over the whole area of the clay liner, and percolate down as if the FML was not there. With clay liner soils that contain some rock, it is sometimes proposed that a woven geotextile be placed on top of the soil liner under the FML to prevent the puncture of rocks through the FML. A woven geotextile between the FML and the clay, however, creates a highly transmissive zone between the FML and the clay. The surface of the soil liner instead should be compacted and the stones removed so that the FML can be placed directly on top of the clay. 

With a liquid flowing across the plane of the material, as in a geotextile filter, the permeability perpendicular to the plane can be divided by the thickness, T, to obtain a new value, permittivity (see Figure 26.23). In crossplane flow, T is in the denominator for planar flow, it is in the numerator. Crossplane flow is expressed as... 

ASTM, Standard Test Methods for Water Permeability of Geotextiles by Permittivity, ASTM D4491-99a(2004)el, American Society for Testing and Materials, West Conshohocken, PA, 2004. 

Polymeric stabilizer materials are a subset of a much larger recent development in civil engineering. ASTM has defined a geosynthetic as a planer product manufactured from polymeric materials used with soil, rock, or other geotechnical-related material as part of a civil engineering system. A geotextile is a permeable geosynthetic made of textile materials. 

From the above description of the basic geo-filtration mechanism, it becomes evident that the performance of geotextiles as filter media depends largely on two properties the material s cross-plane permeability and pore-size characteristics. 

The fifth example study has shown that using sand encapsulated in geotextile containers for the core of rubble mound breakwaters, which is about one order of magnitude less permeable than a conventional core made of quarry run, may provide many advantages. This is particularly the case when rock material (quarry run) is... 

Hexibility, permeability and ability to cross-flow of water make natural geotextiles a good material to protect riverbanks and embankments from attack by floodwater and seashores from attack by wave surge. The favourable circumstances of natural geotextiles on the environmental are significantly more important wherever slopes to be protected are in contact with water. 

---