Master of Science By Research
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- item: Thesis-AbstractIdentification of rock weathering by conventional methods and image analysis techniques(2023) Kanagasundaram, G; Dassanayake, ABN; Jenaayawardna, CL; Chaminda, SPObservations on weathering patterns are a crucial aspect of geotechnical analysis, as they allow the determination of site quality for various civil and mining engineering applications. There are traditional methods available to assess weathering and the effect of weathering on rock properties. In this study, selected set of laboratory testing were performed to identify the key properties of rock using representative samples from ongoing three quarry sites. The study reveals that fresh rock samples from all three quarry locations maintained a durability of over 98% through four cycles of the slake durability test. Nonetheless, these same samples exhibited decreased strength, which can be attributed to their mineral composition and internal structural arrangements of rock samples tested. Moreover, the overall findings indicate deteriorating values for the tested rock properties which could possibly be caused by rock weathering. Therefore, an attempt was made to look at using the modern technology how accurately the weathered surfaces can be identified and classified. For this purpose, machine learning (ML) techniques with remotely sensed Unpiloted Aerial Vehicles (UAVs) images were utilized. The analysis yielded an impressive F1 score of 0.88 to classify weathering in general. However, the attempts to classify different weathering grades yielded marginal results. These limitations are primarily due to factors such as the number of bands, the spatial resolution of the UAV sensors, and the availability of training data for the ML algorithm. Nonetheless, this study serves as a promising first step in demonstrating the potential of UAVs and appropriate ML models for the classification of weathering patterns, which can be further optimised and deployed for real-time observations. It is highly recommended that laboratory sample testing be carried out in conjunction with image analysis to ensure a detailed and comprehensive understanding of the test results. Keywords: Rock properties, Microstructure, Machine learning
- item: Thesis-Full-textInsights into the heterogeneity of coal fly ash waste(2024) Kanesalingam, B; Jayawardena CL; Fernando A; Amarasinghe DAS; Attygalle DCoal is a well-known workhorse for power generation, particularly in developing countries, due to its favourable economic benefits such as low cost, wide availability, and minimal infrastructure. However, coal-fired power plants yield a substantial by-product, known as coal fly ash (CFA), with a global annual output of 1 billion tons during combustion. Only 60% of this CFA is presently used, whereas the rest is disposed of in the environment, contributing to severe environmental pollution. In contrast, CFA is a versatile material that can serve as an adsorbent, fertiliser, and in advanced material applications, offering a promising dimension for its use. This study addressed the multifaceted potential of CFA components, by probing its seldom-explored heterogeneity through advanced characterisation techniques. While existing research has predominantly focused on isolated extractions, neglecting broader applications, this study proposes a comprehensive strategy centred on the strategic implementation of washing cycles. Integral to this approach is an extensive characterisation campaign employing multi-modal imaging techniques, such as scanning electron microscopy and energy-dispersive X-ray spectroscopy combined with state-of-the-art deep learning algorithms and digital image processing techniques. Through these methods, this study uncovered and extracted various valuable constituents from CFA, notably cenospheres and materials conducive to zeolite synthesis, demonstrating their potential as effective adsorption agents. Furthermore, this study pioneered a novel methodology that combined X-ray microanalysis with deep learning to precisely classify and characterise cenospheres. This breakthrough facilitated a comprehensive understanding of these hollow structures and allowed quantification of their imperceptible physical structures to modify them as efficient adsorbents. The results of this study significantly contribute to elucidating the capabilities of CFA as a source of high-performance adsorption agents. By leveraging innovative techniques and holistic approaches, this study advances our understanding of CFA, and offers a pioneering methodology for sustainable waste management and resource recovery. Keywords: Coal fly ash, Cenosphere, X-ray microanalysis, Deep learning
- item: Thesis-Full-textValue addition to local vein quartz in producing industrial grade silicaPathirage, SS; Rohitha, LPS; Ratnayake, NPApplications of high-purity quartz as a raw material in high-tech industry are numerous. A few of them includes semiconductors, microchips, industrial integrated circuits, high temperature lamp tubing, optical fibers, chemically reinforced glass and solar silicon cells. Sri Lanka is rich in quartz mineralization with an abundance of major vein quartz deposits with purity levels over 99.5% of SiO2. Developing high-tech products requires considerable capital investment, expertise and advance processing technologies which are lacking in developing countries like Sri Lanka. Thus leading to export raw quartz with enforced size reduction of run-of quarry quartz in grit and powder forms to industrialized countries without further value addition. Therefore, an alternative approach is evaluated and recommended to achieve a higher level of value addition by exporting semi-processed and processed industry specific quartz raw material. Chemical composition of major types of vein quartz and mining activities of 7 vein quartz deposits and mass scale quartz processing at a plant located in Badulla district of Uva Province, Sri Lanka have been subjected to study. Critical step evaluation of the process in mining, transport and processing activities was carried out with reference to critical trace elements by using isodynamic magnetic separator, inductively coupled plasma optical emission spectroscopy and atomic absorption spectrophotometer. Results show that colourless quartz contains the lowest trace elements concentration while feldspar-associated quartz has the highest. Lowest Fe, Al, Cr, Mn and Ni levels were observed in colourless and milky quartz in selected deposits. Manual chipping of Fe stains reduce Fe levels of 300 ppm while soil contamination increase Fe levels by 375 ppm. Transportation in iron lined trailer has a possibility to increase Fe levels up to 150 ppm due to contact with rust layer. In processing, Fe levels can be reduced by more than 20 ppm by removing the finer size fraction in each crushing step. Further reduction can be obtained to a level below 9 ppm by dry magnetic separation with 10,000 gauss 24 trays magnetic separators. Through selective mining and exercising quality control in mining, transportation and processing activities, industry specific quartz raw material can be produced.
- item: Thesis-Full-textEnhancing physical properties of recycled aggregates with rice husk ash-cement mixtureKariapper, A.B.Y.; Karunarathne, S; Nanayakkara, DThe high water absorption of recycled coarse aggregates (RCA) is a major drawback when it is considered as an alternative material for natural coarse aggregates (NCA). It is mainly due to the porous old attached mortar on the surface of RCA. This study presents an effective method to treat the surface of RCA in order to improve its physical properties. The surface of RCA was coated with slurries that contained varying proportions of rice husk ash (RHA), water and lime or cement. The slurry ratios used in the research varied from 0.625 to 2.00. The solid composition of the slurry was varied as required by varying the RHA to lime or cement composition. The treated recycled coarse aggregate (TRCA) coated with a RHA-lime slurry had been cured for 24 hours and the TRCA coated with RHA-cement slurry had been cured for 3, 7, 14 and 28 days. The water absorption of each scenario was analyzed for the respective curing ages. It was observed that the RHA-lime slurry gives a very weak coating around the surface of RCA than that given when RHA-cement slurry is used to coat RCA. Therefore RHA-cement slurry is recommended to treat RCA. When analyzing the results it could be seen that with the increase of RHA present in the slurry the water absorption of the TRCA increases and when the slurry gets thinner the water absorption of TRCA achieves a minimum and as the slurry gets even thinner it increases once again. When RCA was coated with slurry containing 100% cement the optimum slurry ratio that gave the minimum water absorption of TRCA was 1.500 and when a mixture of RHA and cement was used in the slurry the optimum slurry ratio that gave the minimum water absorption of TRCA was 0.875. In most scenarios the highest reduction in the water absorption of TRCA was achieved at a curing age of 7 days. A grade 30 concrete was made with three selected scenarios of TRCA coated with the RHA-cement slurry, RCA and NCA. The concrete scenarios made with the TRCA and NCA obtained strengths greater than 30 N/mm2 after 28 days of curing, except that made with RCA. The proposed treatment method can be used to reduce the water absorption of RCA from 6.01% to 3.53-4.44 %. Furthermore when RCA is treated by using this treatment method the negative impact RCA has on the fresh and hardened concrete properties can also be negated.
- item: Thesis-AbstractOptimization of Sri Lankan underground graphite mining methods, from a view point of rock mechanics and cost(2015-06-24) Hettiwatte, MC; Dharmaratne, PGR; Hemalal, PVAThis research includes the study of the mining method adopted at Bogala Graphite Mines and its suitability compared with other mining methods used in the mining industry. The mining method adopted in Bogala mines has been assessed through this study. It mainly focus on the rock mechanics and financial aspects with comparisons to the mining methods adhered by the Sri Lankan mining industry. The major graphite occurrence discovered more than hundred years has produced highly valued the world over. In Sri Lanka, graphite mineralizations occur in the form of rich veins with steep dips in the South-Western sector of the island, the vast stretch of area which has been famous for graphite mining with thousands of pits in operation during the high demand of the first and second world wars. Where an outcrop is encountered, a pit had been sunk and the steeply dipping vein had been followed to the depths. At Bogala mines, the adoption of Overhand Cut-and-Fill mining method is influenced by the steeply dipping vein environment with rock intercalations and high water inflows with less competent country rock. Although cut–and–fill mining has been traditionally successful ensuring high recovery and safety, only limited studies has been carried out with an engineering input to evaluate this method. With the use of literature and site visits to Bogala mines, the mining method used at Bogala mines, the underground environment and the other mining methods used in the mining industry both internationally and locally have been studied. In evaluating the most suitable mining method, workability, safety and ore dilution and recovery factors of different mining methods were considered and the most suitable method for Bogala mine was evaluated.
- item: Thesis-AbstractInvestigation of the possibility of converting seawater to drinking water in Hambantota area by reverse osmosisIllangakoon, UI; Dissanayake, DMDOK; Walpolage, SHabantota is a district in the southern section of the dry zone, Sri Lanka. The population density 211 per square kilometer distributed variably depending mainly of availability of water and other facilities such as electricity and domestic requirements.4.1 % of total population live in urban areas towns). People who live in suburbs are the most affected by the non-availability of safe water for drinking and other domestic purposes. Only 33.4% of households use piped born water and 55.3% use water from wells and 6.2% use water from tube wells. It has been reported that 60% of the ground water is bad quality and according to the World Watch Institute one third of the world population will face water shortages by the year 2020. This would create a situation where there will not be enough safe water for human survival. Therefore an attempt was made to convert ground water and seawater to drinking water. In this research, a field study was conducted in Meegahajadura, 81°00' N and 6°21' E, a small village in Suriawewa Division from the north sector of the Hambantota District. Ten ground samples were taken from ten locations, from tube wells, which were 8 km radius from Meegahajadura junction. The water samples were chemically analyzed. The chemical properties of the ground water samples tested varied drastically due to its association with the local variations of superficial mineral deposits, lake deposits, paddy alluvium which are 'of variable compositions and dry soil. The number of samples tested was not adequate enough to find a geological trend of hard rock pattern. None of the samples tested were up to the permissible limit of drinking water standards outlined by SLS 614. This and SLS 894 clearly indicates the necessity for ground water treatment prior to drinking, A feasibility analysis was conducted as. a .9ualitative and a quantitative analysis. The research shows it is feasible to desalinate ground water in the Hambantota district to produce drinking water by RO. It is feasible to construct a brackish water RO plant of capacity 10m3 per day to produce drinking water for Meegahajadura. The unit cost of producing drinking water by a seawater RO plant reduces to about US$ I (Rs 100/=) per m3 per day by year 20 l O. It is feasible to produce 40,000 m3 per day by seawater RO plant to fulfill drinking and other domestic water requirements for the Hambantota district by the year 2021. Owing to the complex nature of predicting the operating conditions of the RO permeate water, which varies greatly on feed water quality, operating pressure, temperature, a mathematical model was formulated. The purpose of this formulation is to predict the product water conditions of various feed water having varying values of TDS. The model makes use of the Solution Diffusion Model and it employs feed water concentration of six solutes namely: Na +, Ca2+, Mg2+, Cl, and K+, and as a whole it comprises of 99% of seawater. It was verified experimentally using diluted seawater to predict the product flow rate and TDS, total rejection of solutes, individual concentration of 6 Solutes in the product. This formulated model was verified by running the 75000 GPD RO plant at the university by using diluted seawater as feed water making various concentrations of solutes. Plotting the experimental data and model on the same graph at constant RO pump pressure, it was calculated the error of fit o fthe experimental data to the model. The experimental observations of the product flow rate and TDS, total rejection of solutes, individual concentrations of 6 solutes in the product, the % solute rejection of individual solutes and plant recovery fit the model to an accuracy of less than 16%.
- item: Thesis-AbstractRecovery of silver (Ag) from photo processing effluent by chemical and electro-winning methodsRohitha, LPS; Wijeyekoon, SLJIndustries such as mining and industrial minerals, metallurgical, photo processing, textile, leather and chemical produce wastewater containing heavy metals that are hazardous to man and the environment. Photo processing waste effluents arise from X-ray, lithographic and photo processing operations. The photosensitive medium used in these operations is an emulsion of fine Ag halide matrix in gelatin. During fixing, the Ag" is removed by the fixer solution. The developer and bleach solutions also contain the Ag heavy metal. The recovery of Ag" from such wastewater may be done by electro-winning, metallic replacement, evaporation, ion exchange, reverse osmosis and electrodialysis. The aim of this research was to investigate the application of electro-winning technique for selective removal of Ag metals from photo processing effluent. The laboratory scale electro-winning cell was a beaker of 12.7 cm in diameter and having a capacity of 250 ml. The anode was of stainless steel of size 7.5 x 4.5 cm2. A carbon plate of 1 cm thick (7.5 x 4.5 cm2") of 99.5% carbon was used as the cathode. The circuit consisted of an electrolyte bath a precision type milli-ammeter and an adjustable resistant in series, and a voltmeter connected across the electrodes in the bath. During the electrolysis, samples were taken after 5, 10, 15, 30, 60, 120 & 180 minutes intervals respectively at each of the current density values corresponding to 10, 20, 30, 35, 40, 45, 50, 55, 65, 70, 75, 80, 90, 100 & 110 From each solution three aliquots were pipeted out & analyzed In the electro-chemical method the electrowinned solution was filtered and the residue was treated with. Ammonium Nitrate reagent In the third approach the photo processing effluent was subjected to electro-winning process using a current: voltage ratio of 2.2 to 2.8. In the first approach, industrial photo processing effluent having 2400-Pfm of Ag was subjected to electro-winning technique at current density of 82 mA/cm2. However in three hours, only 14 % of Ag was deposited on the cathode and considerable amount of precipitate was visible at the bottom of the cell. This black precipitate resembled typical AgS precipitate and is thought to be formed due to oxidation of S203 to elemental sulfur that preferentially binds with Ag". The interference from S drastically reduced the recovery potential of Ag at the investigated process condition thus rendering the process technically aid economically non viable. In the second approach, the same effluent was subjected to an electro chemical method giving 14 % of Ag deposition on cathode and 72 % of Ag was extracted from chemical methods. However the use of number of expensive chemicals and heating make this method economically less attractive. The use of very low voltage with a current: voltage ratio of 2.2-2.8 does not provide sufficient energy for oxidation of S203 thus avoiding S interference on Ag" reduction. Under this process condition, a remarkable Ag recovery of 86% was achieved at the current density of 82 mA/cm2. The developed process conditions prove the technical feasibility of electro winning for Ag recovery and stimulate further investigations into optimization of cell configurations for industrial application.
- item: Thesis-AbstractApplicability of phytoremediation methods to treat chromium contaminated watersHettiarachchi, MN; Karunarathne, SChromium is a hazardous metal available in both Trivalent (Cr +3)and Hexavalent (Cr+6) forms. Cr+6 is evidently toxic whereas Cr+3 is relatively less hazardous than Cr+6. Cr+6 and Cr+3are extensively used in many industrial processcs and causes industrial heavy metal pollution of surface and ground water. There are iiany already practiced methods to remove Chromium such as Chemical Precipitation and Ion Exchange etc. Very little research has been done.on Phyto- remediation of Cr+6 and Cr +3 Currently there is a growing interest on research on 11 'L' capacity of Ferns to extract heavy metals. The amazing uptake rate of Pteris vitata (Br. 'dk fern) gave the initial 'impetus to this study. Nephrolepis exaltata or Common Sword Fern is a commonly found hardy invasive fern. It is recorded to be hardy plant with hign moisture and acidity In this study N. exaltata was comparatively assed with few other species for the capability of chromium extraction. N. exaltata showed a good uptake rate. Ability of Nephrolepis exaltata to extract Cr+3 from an artificial solution was studied in detail separately under 'Hydroponic and Soil water systems. All the experi ments were done in a controlled laboratory environment N. Exaltata showed very high removal rates (about ';1)%) in a Hydroponic medium upto 50 ppmcontamination of T-Cr. The mass balance she-ws that most of the Cr taken up by the plant is retained in the roots (about 75 % or 35uO mg/kg). Little is translocated to above-ground tissues (4% or 120 mg/kg). Therefore \he mechanism of removal is mainly Rizofiltration. The mechanism of uptake may be Bio-sorption or Active uptake by root cells. N. Exaltata hardly shows any symptoms of Ph .to-toxic affects upto 50 ppm of Cr +3,and 15 ppm er Cr+6. But in a Soil water system mass balances show that 1110stof water soluble Cr+3 is sorbed to soil (about 90%). N. exaltata is poor- in de-mineral izing, mobilizing and uptake of soil bound Cr +3.Sand has a remarkable capacity to immobilize Cr+3 in water. More research should be done to identify the capacity of sand and gravel to bind chromium.
- item: Thesis-AbstractCommunicating data quality in a GIS environmentThavalingam, K; Puswewala, UGAThe GIS database is a digital representation of the real world. Any abstract of reality will contain discrepancies from its source. With traditional methods many of the problems are visible and the skilled map analyst makes the necessary adjustments and knows how far the information can be relied upon. With a Geographic Information System the equivalent operations are not transparent (the black box effect), usually the operators are no longer so skilled and the problems are largely invisible. The digital modelling has the potential to dramatically increase both the magnitude and importance of errors in the models. The results may be used for decision making and planning despite possessing levels of uncertainty that are completely unknown and usually cannot even be guessed. That is why the accuracy analysis is one of the most important problems in the development and applications of the system. Currently there are several demands from users of data to include quality parameters in the related GIS databases. A number of researchers have done work on the derivation of data quality especially on positional or geometrical accuracies. However there has been little work done on qualitative or semantic accuracies and ways of communicating them. A major contribution toward standardizing the definition, assessment and reporting of GIS data quality has been made by the Data Set Quality Working Group of the National Committee for Digital Cartographic Data Standards. This research, provides an overview of the data quality factors that should be considered when using geographic information, and is intended to explore the possibility of generating and communicating data quality in various ways in a GIS environment. Suitable algorithms, .mainly concerning positional and attribute accuracy assessments, were adopted from relevant literature to determine the data quality parameters at different levels of abstraction, for different data types. The levels of abstraction. considered were overall accuracy parameters at coverage level and specific accuracy parameters referring to entity level. To communicate the data quality to the user different methods such as numerical, graphical and textual messages were adopted .The area for the case study is located in Kegalle district. The feasibility of the reported implementation was assessed by means of the referred case study. The results obtained with this case study were used to draw some conclusions and recommendations regarding the communication of, data quality in a GIS environment.