Geotechnical Evaluation of Reddish Brown Tropical Soils

Laboratory investigations were carried out on reddish brown tropical soils from Moniya, Ibadan Southwestern Nigeria to determine the basic unconfined compressive strength of the soil samples which is an important factor to be considered when considering materials as liners in waste containment structure. Clay mineralogy, major element geochemical analyses were carried out by means of X-ray diffractometry and X-ray fluorescence spectrometry respectively. The engineering tests such as sieve size analyses, Atterberg limits, natural moisture contents, specific gravity and compaction using four different compactive efforts namely reduced proctor, standard proctor, West African standard and modified proctor. The tests were carried out in line with the procedures of the British standard 1377 of 1990 and Head of 1992. The soils were found to contain kaolinite as the major minerals with some mixtures of smectite, muscovite, halloysite, quartzite, biotite and aluminium phosphate. Values of the unconfined compressive strength obtained within 12.5 and 22.5% moulding water contents equal to or greater than 200 kN/m² which is the minimum acceptable value required for containment facilities. The maximum dry density, Mg/m³ ranged between 1.68 and 1.98 while Optimum moisture content, % ranged between 12.3 and 21.2. Hence, unconfined compressive strength values were found to be greater than 200 kN/m² at dry unit weight of 16.20 kN/m³ especially when WAS and modified proctor compactive efforts were used which met the minimum required unconfined compressive strength of 200 kN/m² for hydraulic barriers in waste containment facilities.     

Reliability Assessment of Reddish Brown Tropical Soil as a Liner Material

The use of first order reliability method to assess reddish brown tropical soils as potential materials for liners and covers was studied. A procedure was developed by studying the effects of compactive effort, coefficient of variation and compositional variables like initial saturation, plasticity index and clay content on reliability indices. Three compactive efforts namely British Standard Light (BSL), West African Standard (WAS), British Standard Heavy (BSH) were employed. The F-values of the treatment for the various variables has the highest value for hydraulic conductivity (F = 178), followed by plasticity index (F = 83.7) while the lowest is Clay (F = 12.87). Similarly, with respect to the compactive effort, the F-value for hydraulic conductivity is highest (F = 73,358) followed by plasticity index (F = 4329.6), then clay content (F = 423.12) while the lowest is initial saturation (F = 29.78). BSH should be used in order to attain a minimum hydraulic conductivity (K ≤ 10^?7 cm/s) in the field. WAS can also be used with careful control but an equivalent of BSL should never be used. Generally, the F-values for the compactive effort are higher than those of coefficient of variation, showing the superiority of compactive effort over coefficient of variation on the reliability indices. All the calculated F-values are greater than the F-critical or F-tabulated, which inferred that the effect of these variables is statistically significant. Hence, the reliability model used in this research work is suitable for stochastic modeling of reddish brown soils as suitable material for a landfill liner.     

Influence of Ultrasonic on the Flow Behavior and Disperse Phase of Cellulose Nano-particles at Fluid–Fluid Interface

Natural Resources Research - Nano-particles can localize at oil–water (O/W) interface, reduce residual oil saturation, increase the viscosity of brine and decrease the viscosity of crude oil...