Characterization of Geotechnical Properties of Lateritic Soil-Bentonite Mixtures Relevant to Their Use as Barriar in Engineered Waste Landfills

The purpose of this study was to characterize lateritic soil bentonite mixtures intended for use as low-permeability barrier in municipal waste disposal land ll. Characterization of the soil mixtures included measurement of Atterberg limits, compaction properties, hydraulic conductivity, shear strength, and desiccation shrinkage potential. Accordingly, laboratory tests involving soil mixtures with 0, 2.5, 5, 7.5 and 10% bentonite contents, prepared at varying compaction states (2% dry of optimum, optimum and 2% wet of optimum) and compacted using West African stan- dard (WAS) compactive e ort were carried out. Results show that mixtures with bentonite are adjudged to be suitable materials for liners because they met the statutory hydraulic conductivity requirement (i.e., k ≤ 1.0 x 10-9 m/s). Acceptable volumetric shrinkage strain of ≤ 4% (a maximum allowable volumetric shrinkage found in literature and adopted by most regulatory agencies for barrier material) was maintained by most soil mixtures. Although, slight reduction in shear strength was established, uncon ned compressive strength (UCS) values for all soil mixtures met or exceeded the general speci cation i.e., UCS ≥ 200 kN/m2 required for performance in waste repositories.Keywords: barrier, bentonite, hydraulic structures, lateritic soil, waste land l

Compressibility Characteristics of Compacted Black Cotton Soil Treated with Rice Husk Ash

One dimensional consolidation studies on compacted black cotton soil treated with up to 16% rice husk ash (RHA) at the British Standard light compactive effort was carried out to access the compressibility characteristics. The consolidation characteristics of black cotton soil containing 0, 4, 8, 12, and 16% RHA were observed at different moulding water contents (2% dry of optimum, optimum moisture content and 2% wet of optimum) simulating different field placement conditions. Variations of the soil’s index properties with ash treatment were also observed. The Atterberg limits showed improved index properties; plastic limit of the soil was found to increase while the liquid limit and plasticity index decreased with increased RHA treatment. The optimum moisture content (OMC) was observed to increase while Maximum Dry Density (MDD) decreased with increased RHA treatment. The swelling pressure decreased with increased RHA content. The consolidation parameters also showed appreciable changes; with the gross yielding stress irrespective of the particle state increasing with increased RHA treatment. The compression index decreased with increased RHA content but increased with increasing moulding water content. The coefficient of volume compressibility, coefficient of consolidation generally decreased with increased loading pressure and RHA treatment for up to 8%.  The coefficient of permeability decreased with increased RHA content for up to 8%. These results show an overall improvement in the consolidation properties for up to 8% treatment; suggesting the suitability of the material in fills for embankment and low lying marginal land for foundation works. This also helps in ameliorating the environmental problems associated with the disposal of waste rice husk ash

Effect of Fines Content on the Engineering Properties of Reconstituted Lateritic Soils in Waste Containment Application

A lateritic soil reddish brown in colour was reconstituted with inclusion of nes content in 0, 20, 40, 60, 80 and 90% to form six (6) dierent soil mixes (S1, S2, S3, S4, S5 and S6, respectively). These soils were analysed to determine the eect of nes content on their engineering properties. Tests were carried out to determine index properties, compaction characteristics, strength properties (unconned compressive strength (UCS) and undrained shear strength parameters) and hydraulic properties of the reconstituted soils. Specimens used for the determination of UCS, undrained shear strength parameters and hydraulic properties were prepared at the optimum moisture content (OMC) and compacted using the British Standard light, BSL (standard Proctor) energy. Reconstitution of the natural soil (0% nes content) yielded soil samples having fines content between 61 and 93%, and grading modulus that decreased with higher nes content. The specic gravity of the reconstituted soils decreased, while the Atterberg limits as well as derived plasticity parameters increased with higher nes content. The maximum dry density (MDD) and OMC decreased and increased, respectively, with higher nes content. The UCS and angle of shearing resistance generally decreased while cohesion increased with increase in nes content. The hydraulic properties improved with higher nes content. Test results indicate that the reconstituted lateritic soil samples meet the relevant requirements for materials to be used as hydraulic barrier in waste containment structures.Keywords: compaction, derived plasticity parameters, hydraulic barrier, hydraulic conductivity, reconstituted lateritic soi

The geotechnical properties of black cotton soil treated with crushed glass cullet

This study is an investigation into the effect of crushed glass (glass cullet), a waste material, on some of the geotechnical properties of Black Cotton Soils (BCS) of North-Eastern Nigeria. The investigation includes evaluation of properties such as consistency limits, index properties, shear strength parameters, Unconfined Compressive Strength, California Bearing Ratio, permeability and potential volume change of the soil with up to 20% glass cullet content. The results obtained showed that the liquid limit and plastic limit decreased with an increase in glass cullet content, while the plasticity index increase with an increase in glass cullet content. The specific gravity increased with an increase in glass cullet content. It was also discovered that increase in glass cullet content decreased the Optimum Moisture Content (OMC) and increased the Maximum Dry Density (MDD) in Compaction. The Optimum Moisture Content (OMC) from the Compaction test was used to prepare the samples used in Direct Shear test (Shear Strength Parameter test), Unconfined Compressive Strength (UCS) test, Permeability test, California Bearing Ratio (CBR) and Potential Volume Change tests. From these tests, cohesion was found to be decreasing with increase in glass cullet content and the angle of internal friction increases as the glass cullet content increased. The Unconfined Compressive Strength test (UCS), permeability test and California Bearing Ratio test (CBR) increases as glass cullet content increased. Also the swelling pressure reduced with increased glass cullet content. These results reveal the suitability of the material in improving the geotechnical properties of the soil and a potential solution to the environmental nuisance created by glass cullet.Keywords: Black cotton soil, Glass cullet, Geotechnical properties