A New Approach for the Design, Construction and Control of Compacted Mineral Liners of a MSW Landfill Capping

Design parameters typically used for the mineral liner of landfill cover system (e.g. water content w, dry density ρd and hydraulic conductivity k) are often difficult to obtain on site. After construction, these experimental parameters need to be checked against the predicted values. In this paper, a rigorous procedure for design, construction and control of a compacted mineral liner in a capping multilayer system has been developed. The procedure has been schematically subdivided in three phases. The first phase (design) was based on a wide preliminary set of laboratory tests, composed of classification, compaction and permeability tests. An analytical relationship among degree of saturation Sr, dry density ρd and hydraulic conductivity k is also defined. The second phase (construction) was developed through a suitable compaction of the mineral liner planned after the design phase. The last phase (in-site control) consists of checking the design parameters (w, Sr, ρd, k) actually achieved on site. A comparison between coefficients k, obtained through site permeability tests and an analytical relationship obtained in the design phase, was made successfully. Owing to this new approach, it will no longer be necessary to perform in situ permeability tests, but it will be enough to define the above-mentioned analytical relationship during the design phase. In this way, a dangerous damage to the mineral liner, caused by the execution of invasive permeability tests, will be also avoided.