STABILISATION OF NIGER DELTA FAT CLAY WITH BLEND OF BINDERS FOR SUBGRADE APPLICATION - PART 1

Construction of roads on fine-grained soils without any form of stabilisation is a major problem all over the world. In this study, a fat clay having poor subgrade rating (A-7-6) was mixed with blends of sand, drill cuttings ash (DCA), lateralite, and Portland Cement (PC) to improve its plasticity, California Bearing Ratio (CBR), and swell. The sand effected better particle grading of the clay and addition of PC increased its strength. Blends of DCA-PC and lateralite-PC effected friability, improved workability, and also increased the strength of the soil. Blends ratio: sand-PC (4:1); DCA-PC (1:1); and lateralite-PC (2:1) gave the best stabilising effect on the fat clay. The improvements noted were: plasticity index < 30, soaked CBRvalues > 20% after 24 hours and >10% after 96 hours, low swell (0.002 – 0.008%). Thus, this study revealed that the fat clay could be optimised for subgrade application using these stabilising additives. http://dx.doi.org/10.4314/njt.v36i3.1

Stimulation Modelling of the Effect of Internal Migration on Urbanization in Rivers State, Nigeria

Internal migration is defined as “a movement of people from one area of a country (especially one local government area) to another area of the same country for the purpose or with the effect of establishing a new residence” either temporarily or permanently, is a complex and multidimensional process. In this study we are expected to determine the impact of internal migration in Port Harcourt city and Bori town respectively and to show the effect of the variation of some parameters that affect the growth of Port Harcourt city, through Simplified Assumptions and Mathematical Formulations. The internal migration of effective working population from Port Harcourt city to Bori town is lesser than that of Bori town to Port Harcourt city due to lesser jobs and social infrastructural facilities in Bori than Port Harcourt. Method of Analysis used is a non-linear ordinary differential equation of order 45 which otherwise is called O.D.E 45(Matlab ODE 45). It is evident from the results of the study that the variation of the rate of internal migration can produce either a positive or a negative effect on the population growth patterns of the two interacting population predictions

Comparative Analysis of Cement and Lateralite on the Engineering Properties of Niger Delta Soils for Pavement Construction

This is the final published version. It first appeared at http://sciencedomain.org/abstract/9224.This study investigated the effect of cement and lateralite in improving some engineering properties of Niger Delta soils, classified as clayey soil, silty/clayey sand, and fine sand. Cement had very good effect in reducing the plasticity of the clayey soil and the silty/clayey sand but increased the plasticity of the fine sand, and all the samples had increased soaked CBR and UCS at 28 days especially with 6% and 8% cement contents. 14% lateralite content had the best effect on the silty/clayey sand in reducing the plasticity and increasing both the CBR and UCS. However, no positive effect on the plasticity indices was noticed for the clayey soil and the fine sand, but appreciable increases in their unsoaked and soaked CBR and UCS at 28 days curing. The applications of cement (6% and 8%) and 14% lateralite would make the stabilized soils applicable as sub-base and base materials.The sponsorship of the PhD program of the first author by Schlumberger Faculty for the Future Foundation at the University of Cambridge, United Kingdom and the funding by Cambridge- Africa Alborada Scheme of this study which formed part of the PhD research are acknowledged

USE OF DRILL CUTTINGS ASH AS STABILISING AGENT FOR SELECTED NIGER DELTA SOILS FOR ROAD CONSTRUCTION

his study investigated potential of the use of Drill Cuttings Ash (DCA) in the stabilisation of Niger Delta soils for road construction. Most of the in-situ soils encountered in the region are fine-grained and highly plastic that would require special treatment. Four soil samples were obtained and the following tests were carried out: classification, compaction, California Bearing Ratio (CBR), and Unconfined Compressive strength (UCS). Dry DCA quantities ranging 2 – 8 percentages by weight of the soil was added to the air-dried soils for the stabilisation process. They were classified as A-6 (clayey soil), A-2-6 (clayey sand), A-3 (silty fine sand), and A-4 (silty clay soil). Generically, the unstabilised soils were fine-grained having low to medium plasticity, with low shear strength. Other results showed that 6% DCA content caused improvement in the texture, plasticity, and dry density of the clayey soil, while its CBR and UCS parameters compared favourably well with the unstabilised soil values. Also, there was increase in CBR value of the clayey soil after soaking for 24 hours. DCA increased the plasticity of the clayey sand, silty fine sand, and silty clay soil, and there was no substantial improvement in their strength properties. These results showed that DCA would be useful in improving clayey soilswhich are known to be prone to excessive swelling and difficult to handle during construction especially after heavy rainfall.     &nbsp

Comparative Evaluation of Batch and Continuous Anaerobic Digesters in Biogas Production from Municipal Solid Waste using Mathematical Models

An investigation was conducted into the suitability of either of the batch or continuous (CSTR) digesters for anaerobic degradation of municipal solid waste (MSW) in the production of biogas. Mathematical models were developed for the design and evaluation of the two systems. The development of the models was based upon a material balance analysis of the digesters'operation. A Microsoft Visual Basic Version 6.0 Programme was developed for the solution ofthe model equations, and the digesters' operations simulated over a range of percentage total solids (PTS) concentration of 4-10% for the CSTR and 4-30% for the batch digester, and fractional conversion of 0.2-0.8. The results of the simulation show that although the amount of methane (0.0764m3) produced per unit volume of the batch digester is about 4 times less than the amount (0.284m3) per unit volume of the CSTR, the cost per unit volume of the batch digester ($5.98) is 6 times less than that of the CSTR ($33.8), suggesting that the overall cost of producing gas with the batch digester would be more economical. So, it was deduced that the batch digester is better suited for the digestion of MSW for biogas production, compared to the CST

Effect of Total Solids Concentration of Municipal Solid Waste on the Biogas Produced in an Anaerobic Continuous Digester

Municipal Solid Waste (MSW) contains a relatively large amount of organic matter, which decomposes by the actions of microorganisms under anaerobic conditions to produce biogas. The total solids (TS) concentration of the waste influences the pH, temperature and effectiveness of the microorganisms in the decomposition process. This work investigated various concentrations of the TS of MSW in an anaerobic continuously stirred tank reactor (CSTR) and the corresponding amounts of biogas produced, in order to determine conditions for optimum gas production. Five laboratory-scale anaerobic batch digesters of 5 litres volume each were set up for the digestion of 2kg of shredded MSW diluted to a %TS concentration of 26.7%. The results from the batch experimentation were adapted to the design of a CSTR for the digestion of MSW. The CSTR was simulated over a range of %TS concentration of 4-10, at a maximum fractional conversion of 0.8 to cater for system inefficiencies. Mathematical models were developed for the process and solved using the Microsoft Visual Basic version 6.0 Programme. The results show the amount of biogas produced as a power function of the %TS concentration, indicating that as the process continues, a time comes when any marginal increase in the %TS concentration would no longer contribute to the increasing volume of biogas produced. The results further show that, given the limiting upper boundary of the %TS concentration, optimum biogas production in a CSTR digesting MSW cannot be ascertained with the concentration of the %TS alone

Monitoring of microbial hydrocarbon remediation in the soil

Bioremediation of hydrocarbon pollutants is advantageous owing to the cost-effectiveness of the technology and the ubiquity of hydrocarbon-degrading microorganisms in the soil. Soil microbial diversity is affected by hydrocarbon perturbation, thus selective enrichment of hydrocarbon utilizers occurs. Hydrocarbons interact with the soil matrix and soil microorganisms determining the fate of the contaminants relative to their chemical nature and microbial degradative capabilities, respectively. Provided the polluted soil has requisite values for environmental factors that influence microbial activities and there are no inhibitors of microbial metabolism, there is a good chance that there will be a viable and active population of hydrocarbon-utilizing microorganisms in the soil. Microbial methods for monitoring bioremediation of hydrocarbons include chemical, biochemical and microbiological molecular indices that measure rates of microbial activities to show that in the end the target goal of pollutant reduction to a safe and permissible level has been achieved. Enumeration and characterization of hydrocarbon degraders, use of micro titer plate-based most probable number technique, community level physiological profiling, phospholipid fatty acid analysis, 16S rRNA- and other nucleic acid-based molecular fingerprinting techniques, metagenomics, microarray analysis, respirometry and gas chromatography are some of the methods employed in bio-monitoring of hydrocarbon remediation as presented in this review