Suitability of Boulder Marl and Marsh Clay as Sealing Substrates for Landfill Capping Systems—A Practical Comparison

Abstract

The effects of compaction on soil shrinkage behavior need to be considered for engineering long-term durable mineral liners of landfill capping systems. For this purpose, a new three-dimensional laser scanning device was coupled with a mathematical-empirical model to simultaneously determine the shrinkage behavior of a boulder marl (bm) and a marsh clay (mc). Therefore, both materials were precompacted in 200 soil cores (100 cm 3 ) on the basis of the Proctor test results with five different degrees of compaction (bm1-bm5; mc1-mc5). Thus, the shrinkage behavior, intensity, and tendency were determined during a standardized drying experiment. The volume shrinkage index was used to describe the pore size dependent shrinkage tendency and was classified as high to very high (11.3-17.7%) for the marsh clay and medium (5.3-9.2%) for the boulder marl. Additionally, only the boulder marl (bm2), compacted up to 88% of Proctor density, could be installed as landfill bottom liner in drier locations if the local matric potentials did not exceed the previously highest observed drying range (i.e. values below −300 hPa), to avoid crack formation and generation.

Effect of artificial soil compaction in landfill capping systems on anisotropy of air‐permeability

“…3 and 4) and therefore less pronounced differences in pore size distribution following Groenevelt et al (1984). This predominant isotropic behavior also indicates the beginning of the proportional shrinkage phase as mentioned by Beck-Broichsitter et al (2018b, 2018c followed by changes in the inter-aggregate pore space; the stage is also characterized by the formation of additional vertical and horizontal tensile and shear-induced shrinkage cracks (Chertkov, 2014). Note that the differences in blocked air-filled pore spaces between non-rigid and rigid conditions (Tab.…”

“…where θ v is the volumetric water content (cm 3 cm −3 ). The soil pore size distribution was obtained from the slope of the soil water retention curve (SWRC) ( Ding et al, ; Beck‐Broichsitter et al, ): …”

“…The first peak of the ‐function was described by the structural pores denoted here as wide coarse pores (wCP) of equivalent pore sizes of 300 ≤ d > 50 μm (−10 ≤ ψ m > –60 hPa). The second and third peaks ( i.e ., matric peaks) of the ‐function were described by textural pores such as narrow coarse pores (nCP) of 50 ≤ d > 10 μm size (−60 ≤ ψ m > –300 hPa), medium‐size pores (MP) of 10 ≤ d > 0.2 μm (–300 ≤ ψ m > –15000 hPa), and fine pores (FP) of d ≤ 0.2 μm (ψ m ≤ –1500 hPa) as proposed previously ( Beck‐Broichsitter et al, ).…”

“…10°19 E) in Schleswig-Holstein (Northern Germany) was actively operated from February 1977 to May 2005 and about 2.0 million tons of municipal domestic wastes were deposited in it. In 2008, a mineral capping system was installed and the used glacial till was mechanically compacted until the Proctor optimum was reached (Beck-Broichsitter et al, 2018c).…”

“…The undisturbed soil cores were derived from two soil profiles of the mineral capping system that is subdivided into a recultivation liner [organic matter-rich topsoil (0-0.05 m), an intermediate, organic matter-poor layer (0.05-0.4 m), and organic matter-poor subsoil (0.4-0.7 m)] and a sealing liner (0.7-1.0 m) that consists of differently compacted glacial till (Beck-Broichsitter et al, 2018b, 2018c. The first 0.05 m of the soil profile are characterized by a crumbly structure, while a prismatic-platy structure is predominant in 0.2, 0.5, and 0.8 m depths.…”