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Journal Cover Engineer : Journal of the Institution of Engineers, Sri Lanka
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  This is an Open Access Journal Open Access journal
   ISSN (Print) 1800-1122
   Published by Sri Lanka Journals Online Homepage  [49 journals]
  • The Combined Effect of Temperature and Salinity on the Mechanical
           Behaviour of Well Cement

    • Abstract: Carbondioxide Capture and Storage (CCS) has been identified as the best measure to reduce the concentration of carbon dioxide in the atmosphere. Carbon dioxide expedites global warming. The captured carbon dioxide is stored in deep underground reservoirs using injection wells. The integrity of these wells needs to be ensured to have a durable carbon dioxide sequestration. Generally, the well cements of these underground wells lose their integrity primarily due to their degradation caused by aggressive curing temperatures and also due to the salinity conditions prevalent in the earth’s down-hole. Therefore, the aim of this study was to ascertain the combined effect of the temperature and the salinity on the mechanical behavior of well cement. Sulphate resistant Class G cement samples were cured in various salinity concentrations (0 to 40% of NaCl of the weight of water) and at varying curing temperatures (25, 40, 60 and 80ºC). The mechanical behavior of well cement under these varying salinity and temperature conditions was studied by analyzing its uniaxial compressive strength and the Young’s modulus. Scanning Electron Microscope (SEM) images of degraded samples showed microstructural variations caused during the degradation process. EDX (Energy Dispersive X-Ray Spectroscopy) tests were also carried out to find out the proportion of chemical ions in the degraded cement samples. The test results revealed that the uniaxial compressive strength of the samples initially increases up to an optimum salinity of 10% (by weight of water) and that it thereafter gradually decreases with increasing salinity. With the compressive strength varying with the curing temperature, the optimum temperature for 7 days of curing is found to be 40˚C and that for 28 days of curing is found to be 60˚C. On the whole, OPC sulphate resistant well cement shows its optimum strength at 60ºC and at a NaCl concentration of 10%. Published on 2017-02-09 00:00:00
       
  • From the Editor Vol.50 (1)

    • Abstract: No abstract available Published on 2017-02-09 00:00:00
       
  • Comparison of the Stabilization Behavior of Fly Ash and Bottom Ash Treated
           Expansive Soil

    • Abstract: Expansive soil swell on absorbing water and shrink when that water gets evaporated. Because of this alternate swelling and shrinkage of expansive soil, the civil engineering structures built on them get severely damaged. Ground improvement using mechanical and chemical methods can be a mitigation measure. In this research, chemical stabilization was used as a ground improvement technique. The variation of the compaction characteristics, Atterberg limits, Unconfined Compressive Strength (UCS) and swell pressure were tested using separately ASTM Class F fly ash (low calcium) and bottom ash as chemical stabilizers at 8 %, 16 % and 24 % of the total weight of the expansive soil. A Scanning Electron Microscopy (SEM) test was also conducted to study the microstructural changes in the expansive soil treated with fly ash and bottom ash. The results indicate that the Maximum Dry Density (MDD) of the stabilized soil increases up to 16 % with fly ash and bottom ash additions and that it begins to decrease thereafter with further additions. The results of the Atterberg limits test reveal that the liquid limit and the plasticity index decrease with both fly ash and bottom ash additions while the plastic limit increases with those additions. The effect of fly ash and bottom ash on the variation of the UCS was observed for three different curing periods (7, 14 and 28 days) as well as for three different percentages of ash content (8 %, 16 % and 24 %). The findings reveal that the UCS increases up to 16 % of ash addition, and that it thereafter starts to decrease with any further addition of fly ash or bottom ash. Furthermore, an increase in the curing period will help to increase the UCS for a given percentage of additions. The microstructure of the stabilized soil becomes more uniform as the the optimum ash content is reached, and beyond this optimum value, the microstructure becomes nonuniform with an abundance of unreacted ash particles. A reduction of the swell pressure by 70% for fly ash and 48% for bottom ash is observed with the addition of admixtures. The main conclusion that can be drawn from this study is that the MDD, UCS and the plastic limit can be increased with the addition of fly ash and bottom ash while swelling, liquid limit and plastic index can be reduced through these additions. Fly ash is also found to be more effective than bottom ash in stabilizing expansive soil. Published on 2017-02-09 00:00:00
       
  • Cement Stabilized Soil as a Road Base Material for use in Sri Lankan Roads

    • Abstract: The elastic modulus of the lower quality coarse–grained sandy materials available in Sri Lanka is higher than the elastic modulus of fine–grained silty and clayed materials. Although these locally available soils can be stabilized using cement, due to the non-availability of appropriate guidelines, several issues can arise when they are stabilized. The strength of the materials can be measured using the California Bearing Ratio (CBR). However in certain specifications, it is the Unconfined Compressive Strength (UCS)that is specified for stabilized material. Therefore, the first phase of this study was focused on identifying the correct way to measure the strength of stabilized materials. The study confirmed that the strength of a Cement Stabilized Soil Base (CSB) should be measured using the UCS. Furthermore, in road pavements with a stabilized base, the most critical tensile stress and strain occur at the bottom of the stabilized layer. To minimize fatigue cracking, this tensile stress at the bottom of the stabilized layer has to be controlled. However, empirical design guidelines used in pavement designs cannot be used to analyse the mechanistic behaviour of pavement layers. Hence, during the second phase of this study, cement stabilized pavements were analysed using a Mechanistic-Empirical Method (MEM). A pavement design chart for pavements with a CSB layer was developed for various subgrade and traffic classes using the MEM software KENLAYER. Published on 2017-02-09 00:00:00
       
  • Development of IDF Curves for Colombo

    • Abstract: Rainfall Intensity-Duration-Frequency (IDF) relationships usually play a major role in the designing and building of water infrastructure. The main purpose of this paper is to show the procedure that need to be followed in the development of IDF relationships using rainfall data collected in Colombo, Sri Lanka. Short duration rainfall data of Colombo recorded over a 30 year period by the Department of Meteorology were used for the study. The procedures to be adopted in screening rainfall data, carrying out frequency analyses, and finally developing the IDF relationships are described. The IDF curves have been developed for 2, 5, 10, 25, 50 and 100 year return periods for durations ranging from 15 minutes to 24 hours. The developed IDF relationships were compared with the IDF relationships presently available for Colombo. The results indicate that the rainfall intensities of Colombo have recently increased. It is recommended that the IDF relationships for other stations in the country also be updated. Published on 2017-02-09 00:00:00
       
  • Techno Economic Analysis of the Use of High Temperature Low Sag (HTLS)
           Conductors in the Sri Lanka‚Äôs Transmission System

    • Abstract: High Temperature Low Sag (HTLS) conductors are introduced with the intention of mitigating some of the disadvantages of the conventional overhead conductors. When compared to conventional conductors, HTLS conductors have better electrical and mechanical characteristics and by using these conductors in overhead transmission lines, some of the complex issues related to power transmissions could be resolved. However, most of the utilities are still in a quandary about using these conductors in place of conventional overhead conductors which have provided a commendable service to them over a period of a century or so. It is because of their lack of experience in using them in the field as well as because of the novel appearance of the conductors. Almost the entire transmission system in Sri Lanka comprises of overhead lines constructed using conventional conductors, especially ACSR conductors. Utility engineers therefore do not have much knowledge on HTLS conductors and also have very little experience in using them. This paper discusses the possibility of adopting the HTLS conductor technology in the Sri Lanka’s transmission system. The properties, behavior and special characteristics as well as the technoeconomic feasibility of using HTLS conductors instead of the conventional conductors are discussed in depth. Lastly, the issues and challenges related to the application of HTLS conductors are discussed. The results of this research will provide valuable information on the possibility of using HTLS conductors in the Sri Lanka’s transmission system. Published on 2017-02-09 00:00:00
       
  • Improvement of Health and Safety in Construction Sites in Sri Lanka

    • Abstract: This research specifically investigated the safety perceptions, attitudes, and behavior of construction workers and the management of safety practices. By analyzing its results, this study demonstrates that a majority of construction companies in Sri Lanka that were considered in the study have very little risk awareness and that they do not consider health and safety as important issues. The aim of this research was to understand from the data gathered and by analyzing the mechanism of injuries, the value of a Health and Safety Policy and prevent preventable accidents and illnesses by ensuring a good reporting system. Published on 2017-02-09 00:00:00
       
  • From the Editor Vol.49 (4)

    • Abstract: No abstract available Published on 2016-11-22 00:00:00
       
  • A Comparison of Methods of Estimating Missing Daily Rainfall Data

    • Abstract: The availability of a long and complete rainfall record is very important for carrying out a hydrological study successfully. However in general, the data series in these records may contain gaps for various reasons. The objective of this study is to analyse the different methods available for filling gaps in rainfall data records and propose a method suitable for a river basin situated in a mountainous area in Sri Lanka. Towards this end, daily rainfall data from ten gauging stations in the upper catchment area of BaduluOya were collected. Seven different techniques were studied to ascertain their suitability. The methods studied were the Arithmetic Mean method, Normal Ratio method, Inverse Distance Weighting method, Linear Regression method, Weighted Linear Regression method, Multiple Linear Regression method and the Probabilistic method. The data generated for the target stations were compared with actual observations made, based on error statistics, Error Standard Deviation (STD),Root Mean Square Error (RMSE) and Correlation Coefficient (CC). The results of the study showed that for target stations that have only one neighbouring station with a high correlation coefficient, the Probabilistic method and the Linear Regression method give good predictions. For stations that have relatively low correlation coefficients with the neighbouring stations, the Inverse Distance Squared method and the Normal Ratio method outperformed the others. To obtain accurate results from the Multiple Linear Regression method and the Weighted Linear Regression method, it is necessary to have a set of neighbouring stations that have fairly high correlation coefficients with the target station. Published on 2016-11-22 00:00:00
       
  • Identification of the Polyethylene Grade Most Suitable for Natural
           Rubber-Polyethylene Blends used for Roofing Applications

    • Abstract: In Sri Lanka, roofing materials are manufactured with clay, metal, plastic, wood and asbestos, and each of these has its own inherent drawbacks. Asbestos due to the economic advantages it offers, is now the most widely used roofing material in the country. However, it has scientifically proven health risks. The Government of Sri Lanka has initiated action to ban the use of asbestos as a roofing material. The focus of this study is on the development of a roofing material formed of rubberthermoplastic blends containing Natural Rubber (NR) and Polyethylene (PE). Polyethylene is being currently used as a roofing material, but since it is lightweight it needs to be anchored tightly to the roof structure. Rubber being an energy absorbing material, can be incorporated into thermoplastics to make the latter more tough. Polymer blending is a current trend which is being used to develop technically advanced new materials from commonly available polymers. Polymer blends has an excellent combination of physicochemical properties of each of their parent materials. Sri Lanka exports natural rubber and thus there is a good opportunity to make value-additions to raw rubber exports. Similarly, the development of a new material will address the current problems associated with the use of asbestos as a roofing material. This study shows the most suitable grade of PE from among its most common grades such as High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE) and Linear Low Density Polyethylene (LLDPE), for blending with natural rubber The best blended composition that will have standard properties of a roofing material such as tensile strength, tear strength, hardness, water absorption level, thermal conductivity etc., is then identified. Published on 2016-11-22 00:00:00
       
 
 
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