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The behaviour of HDPE geomembranes and installation quality control in geotechnical application
(2013)
The German Landfill Ordinance regulates the use of geosynthetics and other materials in the field of waste Containment Systems. It requires a certification of the geosynthetics by the BAM. The certification-guidelines define the state of the art by giving detailed requirements and specifications i the various geosynthetic products used in landfill constructions. According to the German Landfill Ordinance geosynthetic products have to fulfil their function for more than 100 years. Beyond, supported by an advisory board of landfill experts, BAM has developed installation requirements and demands on quality management for production, installation and third party control. The BAM is responsible to define tests and testing criteria for geosynthetics, to include provisions into the certification document and in addition to stipulate requirements with regard to installation procedure and quality management in Germany. All documents of the BAM such as certification guidelines, recommendations and testing specifications which are approved by the advisory board are published in German language on the website and in the Official Gazette*** of the BAM. For the certification one of the basic requirements is that the geosynthetic product is produced with well defined and well reproducible properties. Thus, a sophisticated quality management System is needed. In addition, not only production control, but also a quality assurance for the installation is necessary.
An approach to achieve “zero leakage” is discussed with respect to the experience in Germany, where strict regulations for landfill lining and capping systems have been developed and issued because of large environmental problems related to landfills that accumulated in the 1970’s and 1980’s. Using a thick, high quality HDPE geomembrane (GMB), which is installed free of residual waves and wrinkles in intimate contact with a compacted clay liner (CCL) or geosynthetic clay liner (GCL) of very low permeability, by a qualified, experienced, well equipped and properly third-party controlled installer and which are protected by heavy protection layers designed with respect to long-term performance of the GMB, may result in a liner or capping system of practically no leakage. This is demonstrated by analyzing results of measurements obtained from permanently installed leak detection systems in combination with HDPE GMBs. The survey is based on 32 German landfills with 1,276,500 m² of installed HDPE GMB.
An approach to achieve “zero leakage” is discussed with respect to the experience in Germany, where strict regulations for landfill lining and capping systems have been developed and issued because of large environmental problems related to landfills that accumulated in the 1970’s and 1980’s. Using a thick, high quality HDPE geomembrane (GMB), which is installed free of residual waves and wrinkles in intimate contact with a compacted clay liner (CCL) or geosynthetic clay liner (GCL) of very low permeability, by a qualified, experienced, well equipped and properly third-party controlled installer and which are protected by heavy protection layers designed with respect to long-term performance of the GMB, may result in a liner or capping system of practically no leakage. This is demonstrated by analyzing results of measurements obtained from permanently installed leak detection systems in combination with HDPE GMBs. The survey is based on 32 German landfills with 1,276,500 m² of installed HDPE GMB.
The German landfill ordinance regulates the use of geosynthetics, polymers and leak detection systems (LDS) in the field of landfill engineering in Germany. It governs the certification process and sets a framework for the requirements on these products. The certification guidelines of the BAM Federal Institute of Materials Research and Testing turn these requirements into detailed technical specifications and associated test procedures. The present paper describes the procedure of developing certification guidelines for LDS by BAM and its advisory board. The requirements for the certification of LDS under the terms of the new German landfill ordinance with regard to operation and capability are listed and the technical criteria are described. The performance test for LDS used in connection with geomembranes is discussed in detail.
Like all plastic products, geocomposite drains (GCD) are susceptible to creep and creep rupture. The GCD is slowly and continuously deformed under long lasting shear and pressure forces. The thickness is reduced and thereby the water flow capacity. If the in-plane deformation reaches a critical value in the course of time, shear failure might occur. Likewise, if the thickness reaches a critical value the structure of the drain core might collapse. These effects are shown using data provided by the manufacturers of four different GCD. Long-term water flow capacity and the acceptable limits of shear stress and normal stress (pressure) with respect to shear rupture and drain core stability as well as the lifetime with respect to these failure modes are determined using standard test methods. The design of long lasting geotechnical structures has to take into account these characteristics of the long-tem performance of GCD.
Testing of the oxidative resistance of polyolefin based geosynthetics in
autoclaves at high oxygen pressure has been suggested as an alternative method to
conventional forced-air oven aging. The intention is to shorten considerably the testing
time and to ensure that aging is performed under the condition of rate-controlled
and not diffusion-limited oxidation. We compare data from high pressure autoclave
tests (HPAT) with data from oven aging and water immersion tests at 80 °C. For this,
the stabilization of the samples has to be taken into account. Polyolefin based geosynthetics
are usually stabilized by two types of “packages” of antioxidants (AO), designated
here as P1 and P2. P1 consists of phenols and phosphites, P2 of hindered amine
stabilizers (HAS) in addition to a marginal stabilization P1 of the resin for the manufacturing
process. Phenolic and phosphite AO are quickly consumed in the HPAT.
Failure time is tremendously reduced compared to forced-air oven aging or water
immersion. The results are discussed within the framework of a basic autoxidation
scheme (Wise et al., 1997). The reduction is much greater than expected from theoretical
considerations. Therefore, a direct and degrading reaction of oxygen with the AO
has to be assumed. In case of HAS, the time dependence of the degradation of tensile
properties in the HPAT is significantly different from the dependence observed in
conventional forced-air oven aging and their effectiveness is likewise strongly reduced.
A conclusive interpretation of HPAT results needs a better understanding of
what happens to the AO at high oxygen pressure.
Die Präsentation erläutert die Hintergründe der nationalen Anforderungen für die Verwendung von Kunststoffdichtungbahnen in Deponieabdichtungen. Die Beständigkeit wird diskutiert. Anforderungen an das Qualitatsmanagement während der Produktion der Produkte und der Bauphase werden aufgezeigt und die Auswirkungen auf die langzeitige Funktionserfüllung werden beschrieben.
Plastic products used in geotechnical engineering, so-called geosynthetics, are often made of polyolefins (polyethylene or polypropylene) and stabilized against oxidative degradation by antioxidants (AO). Three types of AO “packages” are used: (P1) phenols and phosphites/sulfides, (P2) hindered amines (HAS) with a marginal stabilization P1 of the basic resin, (P3) a combination of packages P1 and P2 with comparable amounts of phenol and HAS. We report about long-lasting oven aging and water immersion tests at 80 °C of 29 different polyolefin based products (geomembranes, geonets and geotextiles). Pronounced differences in the degradation behavior were found depending solely on the type of AO package. In case of P1, the oxidative degradation is prevented by the AO. Autocatalytic oxidation only begins after depletion of AO and may lead to catastrophic failure depending on the environmental conditions. In case of P2, degradation starts right from the beginning. However, it is decelerated and proceeds gradually. In case of P3, the degradation behavior seems to be a superposition of the characteristics obtained for P1 and P2. Plotting the fractional loss of the AO in P1 and P2 as function of the square root of aging time, we identified two regimes of AO depletion. We suggest to attribute this observation to the different mechanisms of AO depletion.
An approach to achieve 'zero leakage' is discussed with respect to experience in Germany, where strict regulations for landfill lining and capping Systems have been developed and issued because of large environmental Problems related to landfills that accumulated in the 1970s and 1980s. Using a thick, high-quality high-density Polyethylene (HDPE) geomembrane (GM) that is installed free of residual waves and wrinkles in intimate contact with a compacted clay liner or geosynthetic clay liner of very low permeability, by a qualified, experienced, well-equipped and properly third-party-controlled installer, and which is protected by heavy protection layers designed with respect to the long-term performance of the GM may result in a liner or capping system of practically no leakage. This is demonstrated by analysing results of measurements obtained from permanently installed leak-detection Systems in combination with HDPE GMs. The survey was based on 32 German landfills with 1.276.500 m² of installed GMs.