Experimental Acceptance Procedure for Using Cullet in the Gas Collection Layer of MSW Landfill
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ORIGINAL PAPER
Experimental Acceptance Procedure for Using Cullet in the Gas Collection Layer of MSW Landfill Giampaolo Cortellazzo1 • Eugenio Bello`2 • Stefano Busana2 • Marco Favaretti1
Received: 10 June 2020 / Accepted: 16 November 2020 The Author(s) 2020
Abstract The multilayer system of a non-hazardous solid wastes landfill cover, required by most international regulations, includes a granular layer of adequate permeability and thickness for the collection and drainage of biogas. The choice of the most suitable material generally falls on granular soils, containing very low percentages of fines. The paper presents the possibility of replacing natural soils with cullet, obtained by the glass shredding, and widely available on the market. Its hydraulic conductivity with regard to biogas and its granulometric compatibility with the adjacent layers may be initially assessed by means of the usual filter design criteria. Then, its crushing strength, under static and cyclical loads, must be evaluated, since the capping systems are crossed by heavy earthmoving trucks, and consequently, there is the possibility of a change of the cullet granulometric distribution. As cullet is not a conventional material, the usual geotechnical laboratory tests cannot be directly applied to it. The paper suggests an innovative laboratory procedure, defined as a static and cyclical punching test, which allows to evaluate the crushing resistance of cullet by using the traditional apparatus for soil compaction. Keywords Biogas collection layer MSW landfills Laboratory punching tests Filter design criteria
& Marco Favaretti [email protected] Giampaolo Cortellazzo [email protected] 1
DICEA, University of Padua, Padua, Italy
2
Vicenza, Italy
Introduction As regards the cover of non-hazardous municipal solid waste (MSW) landfills, the European Council Directive 1999/31/CE [1] imposes a biogas collection layer (BCL) thickness not less than 0.5 m and requires an adequate protection from clogging. This allows to avoid a geotechnical instability of capping, induced by the build-up of the biogas pressure below the mineral liner. For this reason, the granular material composing of BCL firstly has to satisfy the following retention and permeability criteria: (1) a grain size compatibility with adjacent layers must be achieved on the basis of the usual filter design criteria; (2) the internal self-stability (ISS) of the layer must be guaranteed through the absence of cementing minerals (such as limestones) and elongated grains (that could favor interlocking) and avoiding the migration of the finer particles; (3) the BCL must bear stresses induced by dynamic and static loads (weight of trucks and layers above the BCL) acting during the different phases of its life. The main geotechnical properties of granular materials (stress–strain behaviour, shear strength, hydraulic conductivity) are related to maintaining the integrity of the grains over time. If grains breakage occurs, the finer fraction increases and the aver
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