Geosynthetics

The use of reinforcing geosynthetics in slopes is a commonly used technique in road embankment construction and can be used to stabilise slopes of bunds or dikes. The geotextile types used for soil reinforcement are woven high strength materials or geogrid type of materials. The design with these elements is outside the scope of this Manual. 

There is a large variety in reinforcement techniques with geosynthetics, from a simple horizontally placed reinforcement underneath embankments to steep geo-textile/geogrid reinforced slopes. 

The weight of the fill increases the friction between the geogrid and the soil, preventing the geogrid from being pulled out by the sliding fill mass. 

For the design of geosynthetic elements which need to function in the long term, very high reduction factors have to be accounted for as a consequence of creep and potential damage. 

Carbon black is the usual UV stabilizer in these products. Weathering studies are reported elsewhere. Several other fillers are employed including titanium dioxide, calcium carbonate, and clay. Clays are used in large volumes in secondary liners where bentonites are used as the absorption media. 

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A.STM. Special Technical Publication, no. 1190, ASTM, Phdadelphia, Pa., 1993, state-of-the-art technologies and new developments in geosynthetic... 

The dominant feature of covers currently in use is one or more barrier layers that are intended to stop the natural downward movement of water through the profile of the cover. Conventional and barrier-type covers include several layers, including grass for surface cover. These covers typically include one or more barrier layers made of compacted clay, geomembranes, or geosynthetic clay. Barrier-type covers are more completely described in Refs. 9, 13, and 16-19. The Subtitle D cover is a simplified barrier-type cover with a single barrier layer of compacted clay. It is less expensive than other barrier-type covers and is used in dry climates.20 21... 

The design of cover systems is site-specific and depends on the intended function of the final cover—components can range from a single-layer system to a complex multilayer system. To minimize percolation, conventional cover systems use low-permeability barrier layers. These barrier layers are often constructed of compacted clay, geomembranes, geosynthetic clay liners, or combinations of these materials. 

In more recent applications, several types of ET cover designs also have incorporated synthetic materials, such as geomembranes, which are used to enhance the function of minimizing water into the waste. For example, the Operating Industries Inc. Landfill in California has incorporated a soil layer with a geosynthetic clay liner in the design. The cover system for this site will reduce surface gas emissions, prevent oxygen intrusion and percolation, and provide for erosion control.68... 

The U.S. DOE has sponsored the ALCD, which is a large-scale field test of two conventional designs (RCRA Subtitle C and Subtitle D) and four alternative landfill covers (monolithic ET cover, capillary barrier ET cover, geosynthetic clay liner cover, and anisotropic—layered capillary barrier—ET cover). The test was conducted at Sandia National Laboratories, located on Kirtland Air Force Base in Albuquerque, New Mexico.84 The ALCD has collected information on the construction, cost, and performance that are needed to compare alternative cover designs with conventional covers. The... 

A 0.3-m-thick granular LDS drainage layer with a minimum hydraulic conductivity of 1 x 10 2 cm/s or a geosynthetic LDS drainage layer with a minimum hydraulic transmissivity of 3 x 10 3 m2/s. 

Geosynthetic materials play a key role in liquid management systems. The five major categories of... 

The fourth type of geosynthetic is a GM or an FML. It is the primary defense against escaping leachate and is of crucial importance. 

Source U.S. EPA, Requirements for Hazardous Waste Landfill Design, Construction, and Closure, EPA/625/4-89/022, U.S. Environmental Protection Agency, Cincinnati, OH, August 1989. a U.S. Army Corps of Engineers Test Method. b Geosynthetic Research Institute Test Method. 

This section discusses chemical compatibility (resistance) of geosynthetic and natural liner materials with wastes and leachates. Even in a relatively inert environment, certain materials deteriorate over time when exposed to chemicals contained in both hazardous and nonhazardous leachate. It is important to anticipate the kind and quality of the leachate a site will generate and select liner materials accordingly. The chemical resistance of any FML materials, geonets, geotextiles, and pipe should be evaluated before installation.39... 

U.S. EPA s Method 909040 can be used to evaluate all geosynthetic materials used in liner and LCRSs currently being designed. Method 9090 is used to predict the effects of leachate under field conditions and has been verified with limited field data. The test is performed by immersing a geosynthetic in a chemical environment for 120 days at two different temperatures room and elevated temperature. Every 30 days, samples are removed and evaluated for changes in physical properties. Tests performed on FMLs are listed in Table 26.7. The results of any test should be cross-referenced to a second, corollary test to avoid errors due to the test itself or to the laboratory personnel. 

ASTM, Test Method for Determining the (In-plane) Flow Rate per Unit Width and Hydraulic Transmissivity of a Geosynthetic Using a Constant Head, ASTM D4716-04, American Society for Testing and Materials, West Conshohocken, PA, 2004. 

Time-temperature shifting is used widely in the prediction of creep and creep-rupture in polyester geosynthetics. Creep of oriented polyesters is expressed by a linear or quadratic increase of strain with log (lifetime). The lifetime under constant load is expressed by the semilogarithmic formula ... 

J.H. Greenwood and W. Voskamp, Proceedings of the Second European Geosynthetics Conference, Bologna, 2000, 329. 

Report 158 Geosynthetics, David I. Cook Report 159 Biopolymers, R.M. Johnson, L.Y. Mwaikambo and N. Tucker, Warwick Manufacturing Group Report 160 Emulsion Polymerisation and Applications of Latex, Christopher D. Anderson and Eric S. Daniels, Emulsion Polymers Institute... 

R. M. Koemer, Designing with Geosynthetics, Prentice-Hall, Inc., Englewood Cliffs, N.J., 1986. 

Retention Detention Systems Septic Above-Ground Tanks Meter Pits, Sumps Pumps Geotextiles Geosynthetics Storm Water Quality Units... 

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