Papers by Author: K.J. Osinubi

Abstract: Increase in the rate of generation of household waste (i.e Municipal Solid waste, MSW) in Nigeria necessitated the growing demand for a safe way to dispose MSW. When MSW comes in contact with water, it generates leachates, a poisonous fluid, that are harmful to humans. The use of landfill system for disposal of MSW has been a good approach for waste disposal. This study evaluated the effect of some hydraulic conductivity (H) parameters (i.e void ratio, degree of saturation and microbial suspension) and permeating fluids on the interaction of lateritic soil subjected to varying steps of treatments with Bacillus coagulans (B. coagulans) and subject to leachate environment for landfill application. Soil was mixed with 0 to 2.4 × 10⁹ cells/ml of B. coagulans. After mixing and compaction, Calcium solution was introduced by gravity on the compacted soil samples and were permeated to percolate to a point of partial saturation. After application of Calcium solution, compacted samples were saturated in water for 24 to 48 hours up until fully saturated, thereafter subjected to H test using water as well as leachate as permeating fluids for a period of 91 days. Results show that void ratio values varied in the ranges 0.550-0.471 and 0.481- 0.485 for specimens where water and leachate were used as permeation fluids. Degree of saturation varied meaningfully with permeation fluids. H values varied in the ranges 1.51 x 10^-9 -1.71 x 10^-9 m/s and 6.84 x 10^-10 - 8.27 x 10^-10 m/s for specimens where water and leachates were used as permeation fluids. Soil-leachate interaction study and micro structural investigations revealed that the modified soil is well-matched with leachate and met the regulatory H value of 1.0 × 10^-9 m/s for used in landfill applications.

Abstract: Lateritic soils are pedogenic surface deposits which occur in vast areas of tropical and subtropical regions of the world and find use as construction material in diverse civil engineering aspects. But, the predominance of kaolinitic 1:1 lattice clay mineral and coating of the clayey constituents with sesquioxides limits the ability of the soil from achieving very low hydraulic conductivity, (k) required for some geotechnical/geoenvironmental structures. The present study investigates the influence of low percent bentonite on the hydraulic conductivity of a residually derived lateritic soil. Accordingly, the test programme involved specimens of lateritic soil - bentonite mixtures containing 0, 2.5, 5, 7.5 and 10% bentonite (by dry weight of soil) prepared at different compaction states (optimum, dry and wet of optimum content), compacted with British Standard Heavy, (BSH) compactive effort and permeated in compaction mould permeameter using falling head test method. Results indicate that reductions in hydraulic conductivity values ranged from 1 x 10^-9 to 6.79 x 10^-11 m/s (i.e. two orders of magnitude) as the percentage of bentonite increased from 0 to 10%. Soil mixtures with up to 5% bentonite content recorded the lowest k values at 2% wet of optimum moisture content, beyond which an increase in k followed. For soil mixtures containing 7.5 and 10% bentonite, a continuous decrease in k was observed. Furthermore, a non – linear relationship between log k and bentonite content was established. These results met or exceeded specification requirements for the aforementioned structures which therefore suggest that the potentials of lateritic soils as a geomaterial for the construction of hydraulic structures can be fully realized when treated with bentonite.

Abstract: Laboratory studies to investigate the effect of Bagasse Ash (BA) admixture on the engineering properties of lime treated black cotton soil was carried out. Black cotton soil is classified as A-7-6 or CH respectively. Bagasse ash is obtained from burning the fibrous residue from the extraction of sugar juice from sugarcane. The results obtained show that the moisture density relationship follows a trend of increasing optimum moisture content (OMC)/decreasing maximum dry density (MDD) at the Standard Proctor compaction energy. California bearing ratio (CBR) values obtained are lower than the 80% CBR criterion for untreated base course materials. The peak CBR value obtained was 31% at 8 %lime/ 4%BA. This value meets the recommended criteria for subgrade materials. The Unconfined compressive strength (UCS) at 7 days is lower than the 1034.25kN/m2 evaluation criterion for adequate lime stabilization. On the basis of the soaked CBR and durability values, it is recommended that black cotton soil can be stabilized for road construction using a 8 % lime/ 4 % BA blend of admixture at standard proctor compaction. However, due to the relative high cost of lime and large quantity that shall be required to achieve stabilization, further study and consideration should therefore be given to the use another additive such as cement to augment and lower the percentage of lime and thus the cost of stabilization.