Effect of Compaction on Soil Physical Properties of Differently Textured Landfill Liner Materials
Mineral landﬁll liners require legally-ﬁxed standards including a sufﬁciently-high available water capacity (AWC) and relatively low saturated hydraulic conductivity values (Ks). For testing locally available and potentially suitable materials with respect to these requirements, the soil hydraulic properties of boulder marl (bm) and marsh clay (mc) were investigated considering a deﬁned compaction according to Proctor densities. Both materials were pre-compacted in 20 soil cores (100 cm 3 ) each on the basis of the Proctor test results at ﬁve degrees of compaction (bm1–bm5; mc1–mc5) ranging between 1.67–2.07 g/cm 3 for bm and 1.09–1.34 g/cm 3 for mc. Additionally, unimodal and bimodal models were used to ﬁt the soil water retention curve near saturation and changes in the pore size distribution (PSD). The structural peak of the PSD in the fraction of pore volume between −30 and −60 hPa was more pronounced on the dry side (bm1–2, mc1–2) than on the wet side of the Proctor curve (bm4–5, mc4–5). Therefore, the loss in structural pores can be attributed to an increasing dry bulk density for bm and an increasing gravimetric moisture content during Proctor test for mc. While the mc fulﬁls the legal standards with AWC values between 0.244–0.271 cm 3 /cm 3 , the Ks values for bm between 1.6 × 10 −6 m/s and 3.8 × 10 −7 m/s and for mc between 7.4 × 10 −7 m/s and 1.2 × 10 −7 m/s were up to two orders of magnitude higher than required. These results suggest that the suitability of both materials as landﬁll liner is restricted.