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Geomembrane
A geomembrane is very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid (liquid or gas) migration in a human-made project, structure, or system. Geomembranes are made from relatively thin continuous polymeric sheets, but they can also be made from the impregnation of geotextiles with asphalt, elastomer or polymer sprays, or as multilayered bitumen geocomposites. Continuous polymer sheet geomembranes are, by far, the most common. Manufacturing The manufacturing of geomembranes begins with the production of the raw materials, which include the polymer resin, and various additives such as antioxidants, plasticizers, fillers, carbon black, and lubricants (as a processing aid). These raw materials (i.e., the "formulation") are then processed into sheets of various widths and thickness by extrusion, calendering, and/or spread coating. Geomembranes dominate the sales of geosynthetic products, at U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomembrane Installation
A geomembrane is very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid (liquid or gas) migration in a human-made project, structure, or system. Geomembranes are made from relatively thin continuous polymeric sheets, but they can also be made from the impregnation of geotextiles with asphalt, elastomer or polymer sprays, or as multilayered bitumen geocomposites. Continuous polymer sheet geomembranes are, by far, the most common. Manufacturing The manufacturing of geomembranes begins with the production of the raw materials, which include the polymer resin, and various additives such as antioxidants, plasticizers, fillers, carbon black, and lubricants (as a processing aid). These raw materials (i.e., the "formulation") are then processed into sheets of various widths and thickness by extrusion, calendering, and/or spread coating. Geomembranes dominate the sales of geosynthetic products, at US$1. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landfill Liner
A landfill liner, or composite liner, is intended to be a low permeable barrier, which is laid down under engineered landfill sites. Until it deteriorates, the liner retards migration of leachate, and its toxic constituents, into underlying aquifers or nearby rivers, causing potentially irreversible contamination of the local waterway and its sediments. Modern landfills generally require a layer of compacted clay with a minimum required thickness and a maximum allowable hydraulic conductivity, overlaid by a high-density polyethylene geomembrane. The United States Environmental Protection Agency has stated that the barriers "will ultimately fail," while sites remain threats for "thousands of years," suggesting that modern landfill designs delay but do not prevent ground and surface water pollution. Chipped or waste tires are used to support and insulate the liner. Types There are certain levels of harmfulness in which the different types of trash have; therefore, there are diff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geosynthetics
Geosynthetics are synthetic products used to stabilize terrain. They are generally polymeric products used to solve civil engineering problems. This includes eight main product categories: geotextiles, geogrids, geonets, geomembranes, geosynthetic clay liners, geofoam, geocells and geocomposites. The polymeric nature of the products makes them suitable for use in the ground where high levels of durability are required. They can also be used in exposed applications. Geosynthetics are available in a wide range of forms and materials. These products have a wide range of applications and are currently used in many civil, geotechnical, transportation, geoenvironmental, hydraulic, and private development applications including roads, airfields, railroads, embankments, retaining structures, reservoirs, canals, dams, erosion control, sediment control, landfill liners, landfill covers, mining, aquaculture and agriculture. History Inclusions of different sorts mixed with soil have been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Liner Integrity Survey
Electrical liner integrity surveys, also known as leak location surveys are a post-installation quality control method of detecting leaks in geomembranes. Geomembranes are typically used for large-scale containment of liquid or solid waste. These electrical survey techniques are widely embraced as the state-of-the-art methods of locating leaks in installed geomembranes, which is imperative for the long-term protection of groundwater and the maintenance of water resources. Increasingly specified by environmental regulations, the methods are also applied voluntarily by many site owners as responsible environmental stewards and to minimize future liability. History Electrical liner integrity surveys were initially developed at Southwest Research Institute through funding provided by the U.S. Environmental Protection Agency as a response to the need to control the quality of geomembrane installations. Three technical papers describing the method were published and presented by Southw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geotextiles
Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain. Typically made from polypropylene or polyester, geotextile fabrics come in two basic forms: woven (resembling mail bag sacking) and nonwoven (resembling felt). Geotextile composites have been introduced and products such as geogrids and meshes have been developed. Geotextiles are durable and are able to soften a fall. Overall, these materials are referred to as geosynthetics and each configuration—geonets, geosynthetic clay liners, geogrids, geotextile tubes, and others—can yield benefits in geotechnical and environmental engineering design. History Geotextiles were originally intended to be a substitute for granular soil filters. The original, and still sometimes used, term for geotextiles is ''filter fabrics''. Work originally began in the 1950s with R.J. Barrett using geotextiles behind precast concrete seawalls, under precast c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Puncture Resistance
Puncture resistance denotes the relative ability of a material or object to inhibit the intrusion of a foreign object. This is defined by a test method, regulation, or technical specification. It can be measured in several ways ranging from a slow controlled puncture to a rapid impact of a sharp object or a rounded probe. Tests devised to measure puncture resistance are generally application-specific, covering items such as roofing and packaging materials, protective gloves, needle disposal facilities, bulletproof vests, tires, etc. Puncture resistance in fabrics can be obtained through very tight woven fabrics, small ceramic plates in fabric coating or tight woven fabrics with a coating of hard crystals. All described methods significantly reduce the softness and flexibility of the fabric. The puncture resistance will depend on the nature of puncture attempt, with the two most important features being point sharpness and force. A fine sharp point such as a hypodermic needle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linear Low-density Polyethylene
Linear low-density polyethylene (LLDPE) is a substantially linear polymer (polyethylene), with significant numbers of short branches, commonly made by copolymerization of ethylene with longer-chain olefins. Linear low-density polyethylene differs structurally from conventional low-density polyethylene (LDPE) because of the absence of long chain branching. The linearity of LLDPE results from the different manufacturing processes of LLDPE and LDPE. In general, LLDPE is produced at lower temperatures and pressures by copolymerization of ethylene and such higher alpha-olefins as butene, hexene, or octene. The copolymerization process produces an LLDPE polymer that has a narrower molecular weight distribution than conventional LDPE and in combination with the linear structure, significantly different rheological properties. Production and properties The production of LLDPE is initiated by transition metal catalysts, particularly Ziegler or Philips types of catalyst. The actual polyme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-density Polyethylene
High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, HDPE is used in the production of plastic bottles, corrosion-resistant piping, geomembranes and plastic lumber. HDPE is commonly recycled, and has the number "2" as its resin identification code. In 2007, the global HDPE market reached a volume of more than 30 million tons. Properties HDPE is known for its high strength-to-density ratio. The density of HDPE ranges from 930 to 970 kg/m3. The standard method to test plastic density is ISO 1183 part 2 (gradient columns), alternatively ISO 1183 part 1MVS2PRO density analyzer. Although the density of HDPE is only marginally higher than that of low-density polyethylene, HDPE has little branching, giving it stronger intermolecular forces and tensile strength (38 MPa versus 21 MPa) than ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Resistance
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing."Toughness" Brian Larson, editor, 2001–2011, The Collaboration for NDT Education, [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bond Cleavage
In chemistry, bond cleavage, or bond fission, is the splitting of chemical bonds. This can be generally referred to as dissociation when a molecule is cleaved into two or more fragments. In general, there are two classifications for bond cleavage: ''homo''lytic and ''hetero''lytic, depending on the nature of the process. The triplet and singlet excitation energies of a sigma bond can be used to determine if a bond will follow the homolytic or heterolytic pathway. A metal−metal sigma bond is an exception because the bond's excitation energy is extremely high, thus cannot be used for observation purposes. In some cases, bond cleavage requires catalysts. Due to the high bond-dissociation energy of C-H bonds, around , a large amount of energy is required to cleave the hydrogen atom from the carbon and bond a different atom to the carbon. Homolytic cleavage In homolytic cleavage, or homolysis, the two electrons in a cleaved covalent bond are divided equally between th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulus Of Elasticity
An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is defined as the slope of its stress–strain curve in the elastic deformation region: A stiffer material will have a higher elastic modulus. An elastic modulus has the form: :\delta \ \stackrel\ \frac where stress is the force causing the deformation divided by the area to which the force is applied and strain is the ratio of the change in some parameter caused by the deformation to the original value of the parameter. Since strain is a dimensionless quantity, the units of \delta will be the same as the units of stress. Specifying how stress and strain are to be measured, including directions, allows for many types of elastic moduli to be defined. The three primary ones are: # ''Young's modulus'' (E) describes tensile and compressive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brittle
A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a sharp snapping sound. When used in materials science, it is generally applied to materials that fail when there is little or no plastic deformation before failure. One proof is to match the broken halves, which should fit exactly since no plastic deformation has occurred. Brittleness in different materials Polymers Mechanical characteristics of polymers can be sensitive to temperature changes near room temperatures. For example, poly(methyl methacrylate) is extremely brittle at temperature 4˚C, but experiences increased ductility with increased temperature. Amorphous polymers are polymers that can behave differently at different temperatures. They may behave like a glass at low temperatures (the glassy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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