STRENGTH AND HYDRAULIC CHARACTERISTICS OF COMPACTED SOIL-WASTE MATERIALS ADDITIVE MIXTURES FOR LANDFILL COVER APPLICATION

Abstract

This research investigated the strength and hydraulic characteristics of compacted soil-waste materials additive mixtures for landfill cover application. Waste materials such as: compost– sawdust-eggshell are mixed as C+A, C+B and C+C, where each of the mix were mixed with soils (Igbokoda sand and lateritic soil) as soil-waste materials mixtures in ratio 1:1 and 1:3. The laboratory tests involved the particle size analysis, Atterberg limits, shear strength, compaction, compressibility and hydraulic conductivity of the samples. The particle size distribution of the soil-waste materials mixtures ranges from fine sand to fine gravel, as organic and well- graded sand with classification symbol SW-OL. The maximum dry densities (Ɣd(max)) values of soil-waste materials additive mixtures ranges from 630 to 1100kg/m3 with optimum moisture contents of 16-38.0%. As the moisture content increases, the free air space (FAS) reduced towards the wet side of the optimum moisture content and the degree of saturation increased to a certain optimal moisture content. The strength test was carried out under the normal stresses of 13.63, 27.25 and 40.88 kN/m2 and the values of Cohesion and angle of internal friction of compacted soil-waste materials additive mixtures with mix ratios of 1:1 and 1:3 range from 2.0 to 160.0 KN/m2 and 4.0 to 31.00, The coefficient of consolidation (Cv) values range from 0.351 to 0.591 cm2/min.. The compression (Cc) and recompression (Cr) indices show that the swelling potential of the materials is low for the studied materials. The Cr decreases as the waste materials increased, which means that the samples with a higher waste or sand content have less swelling potential. So also, the values of Cc and Cr decreased when mixed with waste materials mixtures except for C+C mixed with lateritic soils. The hydraulic conductivity values of waste materials mixtures and soil-waste materials mixtures ranges from 1.17 × 10−2 cm/s to 1.97 × 10−2 cm/s and 1.13x 10-2 to 7.73 x10-2 cm/s. Where there is no lateritic soil, C+B:S (1:3) mix can be adopted as biocover and C+C:L(1:1) mix can be used where lateritic soil is the only soil available