Adrian Oshioname Eberemu

Ballast aggregate-supported railway tracks are essential to train operations because they offer a reliable and effective mode of transportation from point of origin to point of destination. However, fouling elements infiltrating the ballast layer significantly compromise its shear strength, thereby affecting the stability of the railway infrastructure. This research investigates the impact of fouling materials on the shear strength of ballast used in the Nigerian railway system. Laboratory experiments were conducted using clean ballast samples as a control and introducing four types of fouling materials at varying percentage levels for comparison. The shear strength of these samples was then assessed using direct shear tests. The results demonstrate that increasing fouling levels in the ballast reduces shear strength across all confining normal stress levels, with a concurrent decrease in the friction angle. These findings underscore that fouling infiltration substantially diminishes the shear strength of ballast. To mitigate this issue, railway engineers must implement proactive maintenance measures and routinely monitor the ballast bed for fouling infiltration to preserve track stability and performance.

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 × 10 ⁹ 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.

The strength of lateritic soil bio-treated with a Bacillus thuringiensis (Bt)-induced calcite precipitate was investigated using a pocket penetrometer (PPT). The effect of bacterial (Bt) and cementation solution concentration (C_s) on the strength of the microbial-induced calcite precipitate (MICP) worked soil was also evaluated. Soil samples were treated with Bt and C_s using three mix ratios (i.e., 25% Bt: 75% C_s, 50% Bt: 50% C_s, and 75% Bt: 25% C_s) based on the natural soil liquid limit (LL = 36.0%). Bt suspension densities of 0, 1.5 × 10⁸, 6.0 × 10⁸, 1.2 × 10⁹, 1.8 × 10⁹, and 2.4 × 10⁹ cells/mL were applied to the soil with four varying C_s concentrations (i.e., 0.25, 0.5, 0.75, and 1 M). The prepared specimens were allowed to homogenise and equilibrate at laboratory conditions. A pocket penetrometer (PPT) was used to test the unconfined compressive strength (UCS) of the prepared specimens at 3, 5, and 7 days after bio-treatment to evaluate the strength of the MICP worked soil at different moisture contents. The results obtained show that the UCS values increased with higher Bt and C_s as well as with a reduction in moisture content as the bio-treated soil equilibrated with the environment. The recorded UCS values for the mix ratios considered were in the order: 50% Bt: 50% C_s > 25% Bt: 75% C_s > 75% Bt: 25% C_s. Therefore, a PPT can be used to determine the approximate unconfined compressive strength of treated soil.

Research and academia have been recently affected by the Coronavirus (COVID-19), and physical classrooms and laboratory experiments have been affected significantly due to the recent laboratory closures. This has led to innovative approaches to curb this problem. To address these difficulties in teaching bioengineering related courses that is of significant interest to students of the Faculty of Engineering in Ahmadu Bello University, Zaria, Nigeria, and of course, useful for engineering-based higher education institutions (HEI), a transitional pedagogy: Communicate, Active, Collaborate, Problem-based Solving, Learning and Assessment (CACPLA), which encompasses blended learning, was developed as a new teaching and learning strategy. In this study, we show that this new strategy can initiate a steady transition from physical classrooms to full online instruction for some subjects in engineering. This method has been trialled as an exercise for a module as part of an envisioned biomedical engineering degree programme which can be integrated with local industries and research institutions in sub-Saharan Africa. The teaching materials and environment were carefully designed and 253 students of third and final year classes participated as the experimental group. Also, the effect of critical thinking, pre-lecture, and post lecture on the overall performance of the students was assessed. Two questionnaires were designed for data collection, (a) for technical questions, (b) for receptiveness. The result of a student survey suggests favourable reception of the teaching methodology, which aided their understanding of the general bioengineering concept as applied to the materials chemistry and mechanical measurements context. It was noticed that 80% of the students indicated that the blended learning method was sufficient in achieving the learning outcomes of the study. The method is envisioned as a useful and sustainable complement to traditional teaching pedagogies and workshops due to the convenience and relatively high accessibility to Zoom and Google Meet Apps which can be readily employed without incurring significant costs.

The effect of bacterial concentrations of Bacillus coagulans and moulding water content (MWC) on the unconfined compressive strength (UCS) of lateritic soil for use as waste containment material was studied. Tests conducted include index test, pH, calcium carbonate content (CCC), and UCS. Soil samples for all tests were mixed with an increasing number of microbes at step suspension densities of 0 up to 2.4 × 10⁹ cells/ml individually. The soil was prepared at MWC of -2, 0, +2, and +4% in relation to optimum moisture content (OMC) and compacted using the Reduced British Standard Light (RBSL), British Standard Light (BSL), West African Standard (WAS) Compaction and British Standard Heavy (BSH) Compaction Energy (CE) respectively. The cementation reagent was added to the compacted samples and allowed to flow by gravity to a point that saturation was reached. Results revealed an increase in pH, while calcium carbonate content values marginally increased from 3.6% at the natural state to 3.9% maximum value at 2.4 × 10⁹ cells/ml. The UCS values increased with a higher number of microbes. Values increased from 204.6, 278.3, 351.3, and 416.8 kN/m² for the natural soil to peak values of 1,036.3, 1,835.5, 2,076.8, and 2,237.3 kN/m² for specimens prepared at -2% OMC and compacted with RBSL, BSL, WAS and BSH compaction energy, respectively. A similar trend was observed for 0, +2, and +4% in relation to OMC. A minimum regulatory UCS value of 200 kN/m² was achieved at MWC of -2, 0, and +2% OMC for all energies. Therefore, it is recommended that CE, moisture content, and the number of microbes should be carefully studied during field construction of a lateritic soil-compacted clay liner in other to achieve the desired result.

A new soil improvement method known as microbial induced calcite precipitation (MICP) has received tremendous attention of researchers in the related fields. This paper reports the results of the compatibility of compacted bio-cemented lateritic soil with municipal solid waste (MSW) leachate. Lateritic soil was treated with Sporosarcina pasteurii (S. pasteurii) suspension densities up to 2.40 x 109 cells/ml and compacted using British Standard light, BSL (or standard Proctor) energy. The permeation with leachate only yielded minimum hydraulic conductivity values of 5.02 x 10-10 m/s for the natural soil and 5.78 x 10-10 m/s for specimen treated with S. pasteurii suspension density of 2.40 x 109 cells/ml. The micrographs of specimens treated with S. pasteurii suspension density of 2.40 x 109 cells/ml and permeated with leachate only depicted the development of bio-film when compared with micrograph of the untreated soil. Test results showed significant reduction in the concentration of the MSW leachate chemical specie considered after interaction with S. pasteurii for 150 days either through bio-transformation or bio-degradation process.