Effect of thermal history on the properties of bentonite

PublishedJournal ArticleThis is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record.© 2016, Springer-Verlag Berlin Heidelberg.The effect of thermal history on the properties of bentonite was studied through a number of experimental tests. The desired thermal history was created on samples of bentonite by keeping them at a fixed temperature (50, 100, 150, 200 and 250 °C) for a specific duration (3, 7, 14 and 30 days). Standard compaction, Atterberg limits, free swelling and swelling pressure tests were carried out on the samples on the dry side of optimum, optimum and wet side of optimum of the compaction curve with desired thermal history. In addition chemical tests were carried out on the flooding water at the end of the swelling test. The results showed that the changes in compaction characteristics were not considerable but the Atterberg limits, free swelling and swelling pressure of the soil were changed due to the thermal history in comparison with the soil without any thermal history. The magnitudes of free swelling and swelling pressure were dependent on the location of prepared sample on the compaction curve. In addition, the changes in Atteberg limits and swelling parameters (amount of free swelling and swelling pressure) were functions of magnitude of temperature and duration of time that the sample experienced the temperature in its temperature history. The effects of temperature and also duration of exposure of the soil to temperature was discussed with the aid of the Diffuse Double Layer (DDL) theory. It was found that the temperature may change the gradation of soil due to cementation of particles as a result of formation of some salts and oxides that help to paste the particles together and change the properties of the soil

Effect of cement on treatment of a clay soil contaminated with glycerol

This is the author accepted manuscript. The final version is available from American Society of Civil Engineers via the DOI in this record.An investigation into the behavior of a contaminated clay soil and its treatment was carried out through a program of experimental tests. The contaminated soil samples were prepared with different percentages (3, 6, and 9%) of a glycerol solution with 40% concentration. The samples were prepared as mixtures of clean or glycerol-contaminated soil with different cement contents (3, 6, and 9%). Atterberg limits and unconfined compressive strength (UCS) tests were conducted on the samples. The results showed that Atterberg limits are reduced by adding glycerol or cement or adding glycerol to soil-cement. Both the strength and stiffness of the contaminated soil are reduced by increasing the degree of contamination. The results of treated soil showed that adding cement to contaminated soil increases the strength and the amount of increase in strength is dependent on the percent of cement, curing time and degree of contamination. Based on scanning electron microscopy analysis, it was found that the presence of glycerol prevents the interaction between soil and cement

Hydrochemical Effect of Different Quality of Water on the Behaviour of an Expansive Soil During Wetting and Drying Cycles

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.The effect of quality of water on deformation, pH, EC (electrical conductivity) and osmotic suction was studied for an expansive soil during wetting and drying tests. The cyclic wetting and drying tests were conducted on samples of an expansive soil in a modified oedometer flooded with distilled, acidic and saline water. During the tests axial deformation of the samples was recorded continuously. pH and EC of pore water and reservoir water were measured through duplicated samples in a conventional oedometer. Osmotic suction was calculated based on the values of EC. The results show that the magnitude of deformation depends on the quality of the water and the deformation attained an equilibrium condition after almost four cycles. pH, EC and osmotic suction decreased with increasing suction. Copyright © 2016 John Wiley & Sons, Ltd

Properties of Clay Soil and Soil Cement Reinforced with Polypropylene Fibers

This is the author accepted manuscript. The final version is available from American Concrete Institute via the DOI in this recordRandomly reinforced cohesive soils can be used as construction material in many civil engineering projects. These materials may be subjected to compressive, tensile or flexural stresses in their life. The presence of stabilizing agents or fibers may affect their resistance against various loads. In this work a clay soil was reinforced randomly at four different lengths of fiber ((10, 15, 20 and 25 mm) [0.394, 0.591, 0.788 and 0.985 in]) with fiber inclusions of 0.5 and 1%. Reinforced soil-cement samples were also prepared with 8 and 10% cement and reinforced similar to the soil. Unconfined compressive and tensile strength tests were carried out on the prepared samples. The results show that the compressive strength is increased with fiber length up to about 10 mm (0.394 in). When length of fiber is larger than 10 mm (0.394 in), the compressive strength is still increased but with a slow rate. The results for the reinforced soil-cement samples indicate that for a given fiber and cement content increasing the length of fiber has no significant effect on the strength of the sample. The tensile strength of reinforced soil is increased by increasing the fiber inclusion and length of fiber. For the reinforced soil-cement samples the tensile strength is increased with increasing fiber content, length of fiber, percent of cement and curing time

Impact of water and solution of glycerol on the treatment of sediment by cement

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this recordIn this paper, the effect of glycerol solution on the behaviour of a sediment of a clay soil and its treatment was investigated through a programme of experimental tests. Laboratory tests were conducted to study settlement of the clay soil in water and in solutions of glycerol with different concentrations. Also, treatment of the sediments deposited in water and solutions of glycerol was investigated by adding 5%, 8% and 10% cement to these sediments. Atterberg limits, compaction and unconfined compression tests were conducted on treated and untreated sediments. Comparison of the results showed that the behaviour of the sediments that were deposited in water and in different solutions of glycerol are not the same. The results also indicted that the cement is effective in the treatment of sediments deposited in solutions of glycerol and for a given percent of cement and curing time, the degree of treatment is dependent on the percent of glycerol in the solution. Increasing the concentration of glycerol decreases the strength of the sediment with time. Based on SEM analysis, it was found that the fabric of the soil deposited in water is different from those of the soils deposited in solutions of glycerol

An analytical approach to probabilistic modeling of liquefaction based on shear wave velocity

This is the author accepted manuscript. The final version is available from Springer via the DOI in this recordEvaluation of liquefaction potential of soils is an important step in many geotechnical investigations in regions susceptible to earthquake. For this purpose, the use of site shear wave velocity (Vs) provides a promising approach. The safety factors in the deterministic analysis of liquefaction potential are often difficult to interpret because of uncertainties in the soil and earthquake parameters. To deal with the uncertainties, probabilistic approaches have been employed. In this research, the Jointly Distributed Random Variables (JDRV) method is used as an analytical method for probabilistic assessment of liquefaction potential based on measurement of site shear wave velocity. The selected stochastic parameters are stress-corrected shear-wave velocity and stress reduction factor, which are modeled using a truncated normal probability density function and the peak horizontal earthquake acceleration ratio and earthquake magnitude, which are considered to have a truncated exponential probability density function. Comparison of the results with those of Monte Carlo Simulation (MCS) indicates very good performance of the proposed method in assessment of reliability. Comparison of the results of the proposed model and a Standard Penetration Test (SPT)-based model developed using JDRV shows that shear wave velocity (Vs)- based model provides a more conservative prediction of liquefaction potential than the SPT-base model

Post-Neonatal Hypoglycaemia and Paediatric Emergency Room Admissions: A Study In The University Of Port Harcourt Teaching Hospital.

Background: Hypoglycaemia, a common complication of many childhood diseases, significantly increases disease-related morbidity and mortality. The objective of this study is to determine the prevalence, morbidity pattern and outcomes of hypoglycaemia at admission of postneonatal children in the Children's Emergency Ward (CHEW) of the University of Port Harcourt Teaching (UPTH).Methods: All post-neonatal children admitted into the UPTH CHEW from September 2007-January 2008 who met the inclusion criteria were prospectively studied using a pre-tested proforma which obtained their sociodemographic and clinical data. In all subjects, plasma glucose was determined on admission (using glucometer and glucose oxidase tests) before management. Data analysis was with EPI Info version 6.04 and statistical significance was set at 0.05.Results: Three hundred and seventy children aged 1month-15 years (mean 36.7±40 months) with 272(78.9%) under-fives were studied. Their plasma glucose levels ranged from 1.0-12mmol/l with 19(5.1%) children among whom were 15(78.9%) under-fives being hypoglycaemic (plasma glucose-1.0-2.4mmol/l, mean 1.4 + 0.2mmol/l). All cases of hypoglycaemia were detected by both methods of estimation. The commonest diseases diagnosed in the study population, irrespective of the plasma glucose level, were malaria, anaemia and diarrhoea. Overall, 49 (13.2%) children of whom 7(14.3%) were hypoglycaemic died. Hypoglycaemia was associated with longer hospital stay and higher mortality rate (36.8%) (p=0.001).Conclusion: Hypoglycaemia, detectable by bedside glucometer test, significantly increases morbidity and mortality associated with common childhood diseases. There is therefore a need for its prevention, early diagnosis and prompt management in all paediatric care settings, especially in resource-limited countries, as recommended in the Integrated Management of Childhood Illness algorithm.Keywords: Hypoglycaemia; Post-neonatal; Paediatric emergencies; Nigeria

Models for predicting the seepage velocity and seepage force in a fiber reinforced silty soil

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Randomly reinforced soil is used in hydraulic projects such as temporary canals, earth dams, stream restoration and so on for controlling seepage. This paper presents an investigation into the effect of random reinforcement on the seepage velocity and seepage force in a silty soil. Experimental tests were carried out on randomly reinforced samples with two types of fiber at different lengths and percentages. The results show that the random reinforcement of soils with fiber is an effective technique in controlling the seepage velocity and seepage force. Regression models were developed based on the experimental data for determination the seepage velocity and seepage force. The proposed models include the length of fiber, fiber content of soil and hydraulic gradient. Comparison between the model predictions and the experimental results shows that the proposed models can satisfactorily predict the seepage velocity and seepage force for a randomly reinforced silty soil. Analysis of the results of the proposed models shows that the seepage velocity increases with increasing the hydraulic gradient but decreases with increasing fiber length and fiber content. In addition the seepage force increases with increasing the fiber length and fiber content of the soil

Effect of Quality Electrolyte Fluid on Removing MTBE from a Clay Soil Using Electrokinetic Technique

This is the author accepted manuscript. The final version is available from ASCE via the DOI in this recordMethyl tertiary butyl ether (MTBE) is a chemical product and the most commonly used gasoline oxygenate. It is characterized as a pollutant for soil and water that has effects on human health. Research on the remediation of soil polluted with MTBE is relatively rare. This paper presents the results of laboratory experiments to study the feasibility of using the electrokinetic technique to remove MTBE from a clay soil. Tests are conducted on a clay soil contaminated with MTBE in a special apparatus, using different quality of electrolyte and direct current (DC) or alternating current (AC) electricity. The results of the tests reveal that, under laboratory conditions, MTBE can be removed from soil using the electrokinetic technique. The efficiency of remediation is dependent on the quality of electrolyte and type of applied electrical current