Master of Philosophy (M.Phil.)
Permanent URI for this collectionhttp://192.248.9.226/handle/123/18722
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- item: Thesis-AbstractDevelopment of a land use/cover monitoring system using satellite images(2004) Jayakody, JAS; Puswewala, UGARemote Sensing and Geographical Information System are modem tools for ecosystem management. Remotely sensed data gives convenient and rapid solutions to problems in a variety of applications. Land is limited, and vital as it is the main provider of important natural resources. The fast growing human population has created many problems, due to the increasing demands for food, water, shelter and fuel. Thus such socio-economic factors often dictate how land is used regionally. Land use affects land cover and in turn, changes in land cover affect land use. Thus land plays a major role in any development process. In tropical countries, due to the impact of human beings, the rates of change in vegetation cover and land use are high. Hence frequent updating of land use maps is necessary to provide the information needed by planners and politicians. The main objective of this research is to investigate the possibility of using different remote sensing satellite images for developing a land use/cover monitoring system. This research is carried out in an area of approximately 400 square kilometres in the southern part of Sri Lanka. Imageries of SPOT, IRS and Landsat satellites are used. Different colour combinations are prepared and false colour composite images are used for image processing. Maximum likelihood method is used for image classification and the overall accuracy of the classifications is more than 90%. Using this classification, change detection matrices are developed to give changes for every land use class considered. A primary problem encountered in the study area is the mixed pixels. It is difficult to separate crop land from residential area, as some people reside in houses within the cultivated area. Filtering techniques can only partially remedy this problem. In order to monitor the land use/cover, image differencing method is applied and the extent of the detected changes in terms of pixels or hectares is calculated. A procedure is proposed as the land use/cover monitoring system using satellite images. Under this monitoring system, the extent of land use/cover changes can be computed by using different satellite images with varied spatial and spectral ranges.certainty.
- item: Thesis-Full-textAppraisal of heat treatment of "GEUDA" gemstones using gas- fired and electrically operated furnace(2021) Jaliya RGC; Dharmaratne PGR; Wijesekara KB“Geuda” gemstones are less valuable corundum variety that has the potential to alter into blue sapphire. “Geuda” is found abundantly in Sri Lanka and it is translucent to opaque corundum with a milky or silky appearance in reflected light and brownish honey colour (or diesel colour) in transmitted light with a basic body colour of a bluish, yellowish or reddish colour. At present, Sri Lankan gem industry commonly adapts gas-fired furnaces for heat-treating “Geuda”, to obtain the desired blue colour, yet recently introduced electric furnaces have also shown potential. It is widely believed that electric furnaces are superior to gas furnaces in achieving the anticipated colour, yet no proper evaluation has been done in this regard. Thus, revealed the optimum conditions and the colouring mechanism for electric furnace heat treatment compare to gas furnace heat treatment, twenty (20) “Geuda” samples were selected and each stone is cut into three similar pieces to compare the colour changes more accurately. The “Lakmini” furnace was used as the gas furnace and the maximum chamber temperature used was 1750oC with a soaking time of 30 min under reducing environmental condition inside the gas furnace. Electric heat treatment carried out at three different temperatures (1300oC, 1500oC,1700oC) and with different soaking times (three days, five days, ten days and one month). Colour enhancement after heat treatment was observed using the GIA colour grading system. Samples were subjected to XRD, FTIR and UV-visible spectrum analysis before and after the heat treatments and XRF for the identification of elements present in the gemstones. The optimum colour alteration occurred in combined heat treatment (1700oC in electrically operated furnace after gas furnace at 1750oC, 30 min). There was a significant peak height drop at 3309 cm-1 in FTIR spectroscopy after the thermal treatment in all samples tested. This peak height drop corresponded to O-H stretching mode water molecules inside “Geuda” stone and it was imperceptible with one month of soaking time. The UV-Visible analysis showed a peak development after heat treatments at 550 nm-650 nm. This is due to the development of blue colour inside the stone as a result of the formation of [FeTi]+6 complex and it was conspicuous in combined heat treatment. d-spaces of the lattice structure in the “Geuda” stones have changed in the stones when analyzed using XRD. XRF analysis emphasized that the Fe:Ti ratio is a critical determiner of blue colour development with combine heat treatment. Geuda stones with a Fe:Ti ratio of 1:7 to 1: 13 produced the desired blue colour. Presence of increased Ti in the stone produced a dark blue colour. The results reported in this study suggest the method of heat treatment, Fe:Ti ratio of the stones and reduced environment inside the furnace are the critical determiners of blue colour development in geuda gemstones.
- item: Thesis-Full-textTechnical feasibility of heavy minerals in Southwestern and Northwestern onshore and offshore regions of Sri Lanka(2018) Kananathan, A; Ratnayake, NP; Weerawarnakula, S; Jinadasa, SUPBeach sediments in Sri Lanka consist of industrial grade heavy mineral occurrences. Most of the previous studies have targeted to identify mineral compositions rather than the provenance of these beach sediments. In this study, the offshore and onshore sediments were collected for identifying heavy minerals compositions. In addition, the long-term coastal morphodynamic changes were analyzed in the coastline of Sri Lanka, with the monsoonal changes. These coastal morphodynamic changes were used to identify the coastal sediment accretion and depositional trends, and its relationship to the heavy mineral provenance. Results suggest the concentration of detrital Ilmenite, Zircon, Garnet, Monazite and Rutile in onshore and offshore sediments in varying concentrations. The heavy mineral potential of the northeastern coast was high (average about 45-50% in the Verugal and 70-85% in the Pulmoddai deposits and 3.5-5.0% in the offshore samples from Nilaveli to Kokkilai (in w/w)), compared to the southwestern sediments (average about 10% in onshore and 2% in offshore Gin River mouth). Therefore, no high economic-grade heavy mineral placers have been discovered by offshore investigations. However, it may be possible to occur concentrated heavy minerals in paleo-river channels that were developed due to glacioeustatic sea-level changes. Observed high concentrated heavy minerals in beach and low concentrated offshore sediments suggest the panning system in the surf zone to form enriched placer deposits. The monsoon-derived longshore currents suggest that the sources of heavy minerals in the Pulmoddai and Verugal deposits may have probably influenced by clastic sediment supply in eastern India and Sri Lanka (the Mahaweli River), respectively. Heavy minerals in the western coast can probably derive from Precambrian metamorphic rocks and supplied to coast through river systems in Sri Lanka. The results obtained are well satisfying for the exploitation of the Verugal deposit and the mine plan was described with the considerations of analytical outcomes.
- item: Thesis-Full-textAlternative phosphorus sources in lake bottom sediments around Eppawala phosphate deposit in Sri Lanka(2018) Dushyantha MNP; Ratnayake N; Jayawardena CLJaya-Ganga is a water canal constructed bisecting the phosphate deposit in Eppawala, Sri Lanka. It nourishes three lakes around the vicinity of Eppawala Phosphate Deposit (EPD). With a view to prospect for unconventional phosphate sources, surface and core sediment samples from three lakes were evaluated, especially to determine the P2O5 concentrations and phosphate solubility. Additionally, surface sediments were analyzed by X-ray fluorescence, X-ray diffraction and laser particle analyzer to evaluate geochemical, mineralogical and textural variations, respectively. Furthermore, selected core samples were subjected to C14 age dating to determine the sedimentation rates, mass accumulation rates and Phosphorus accumulation rates in lakes. P2O5% in the surface lake sediments varied from 0.12 to 1.91 and from 0.33 to 1.24 in upstream and downstream, respectively. In upstream core sediment samples, P2O5% varied between 0.03 and 1.89, however, in downstream core samples, P2O5% varied from 0.01 to 2.22. The solubility of phosphates in lake sediments is typically assessed with respect to 2% citric acid solubility (by P2O5). Aligning with aforesaid, the performed solubility percentage upstream showed 14 to 37 in surface samples and from 4 to 71 in core samples. The corresponding percentages for the downstream samples fluctuated from 8 to 58 and from 1 to 50, respectively. Moreover, geochemical analyses of the surface sediments in both upstream and downstream lakes revealed higher contents of P2O5, TiO2, Al2O3, Fe2O3 and MnO and, low levels of SiO2, MgO, Na2O, K2O and CaO compared with the norms of Upper Continental Crust (UCC) values. The significantly positive anomaly of P2O5 in downstream sediments against UCC comparison is noteworthy. The geochemical classification divulged the chemical immaturity and mineralogical instability of the surface sediments in both areas. Meanwhile, the average Chemical Index of Alteration (CIA) values in upstream and downstream suggested the extreme chemical weathering conditions in the source area. Mineralogical analyses revealed the presence of phosphate-bearing minerals, such as fluorapatite, crandallite and millisite in downstream surface sediments, which are the weathered products of the EPD. Textural studies of surface sediments delineated the nature of material deposition through solid suspensions and favorable depositional condition, in downstream lake. Furthermore, downstream lake showed higher sedimentation rate, Mass Accumulation Rate (MAR) and Phosphorus Accumulation Rate (PAR) over upstream lakes. Interestingly, PAR of downstream is more than five times that of upstream lakes. Overall, results of the study reflected the contribution of the EPD as a phosphate source to the downstream lake and the potential of secondary phosphate mineralization in downstream sediments. High solubility values facilitated the applicability of downstream lake sediments as a low-grade phosphate additive/fertilizer. Continuous nourishment of phosphate-bearing materials via Jaya-Ganga, into the downstream lake sediments, steadily increase the quantity of the phosphate content in downstream sediments and the minable quality of the lake sediments as an economically viable phosphate source in the future.
- item: Thesis-Full-textDevelopment of a methodology to assess the geothermal energy potential in Sri LankaNanayakkara, GD; Premasiri, HMRAssessing geothermal potential is a difficult task. It is a time and money consuming process. There are many methodologies, such as deep drilling bore holes and measure temperature by using thermal sensors, silicon solubility measurement, magneto telluric, etc. The used equipment for these methods, especially for drilling of deep bore holes are much expensive. If geothermal gradient is very low, the area cannot be effectively used to establish a geothermal power plant. Another method based on contents of amorphous silica in hot spring water is also used to determine the geothermal gradient. Main task of this study is to find a suitable cost effective method to assess the geothermal potential in Sri Lanka and to develop a lab scale plant. As a cheaply available geophysical technique, ground resistivity measurement was also used to measure the temperature. Increasing temperature again increases their resistance. This natural phenomenon has been used to develop a methodology to assess the geothermal potential in various countries. Resistivity surveys have been carried out in various places in Sri Lanka. Gathered resistivity data has been analyzed. Geothermal gradient calculation was done in Bogala Graphite Mines to study about the temperature gradient in Sri Lanka. Also this selected place was far away from hot spring areas and hence those hot springs had no influence to the collected data. This method is suitable to find temperature gradient of Sri Lanka. The average values of temperatures in those levels were computed and then geothermal gradient was calculated which is 28.0460C/km. This method gave some reliable information as to how the temperature gradient varies at crustal level of rocks in Sri Lanka. To calculate power generation, a laboratory model was developed with the possibility of applying varying parameters. Collected the annual average temperature data and predicted the temperature gradient of various districts. According to the calculations done, geothermal gradient in Sri Lanka is varying between 23 0C and 30 0C per km. This information has been used to develop the geothermal map of Sri Lanka. Laboratory plant was developed and its performances were studied for varying hot spring temperatures and all data gathered and analyzed. According to that the geothermal temperature gradient in Sri Lanka is suitable to generate electricity. But the water flow rate is not sufficient to produce more power.
- item: Thesis-AbstractSite suitability analysis for water harvesting structures in Suriyawewa, Hambantota district using GIS techniquesSenanayake, IP; Puswewala, UGA; Dissanayake, DMDOKSri Lanka receives an average annual rainfall varying from 900mm to 6000mm. However, the rainfall is not distributed equally over the island. Hence, traditionally, the country is divided into three main climatic zones as wet zone, dry zone and intermediate zone. Two thirds of the island is occupied by the dry zone, which receives less than 1750mm of average annual rainfall. The dry zone periodically has faced water stress conditions from the past, and Hambantota District appears to be a severely affected area, on the basis of surface water availability. With the ongoing development projects, the demand for water in the district will increase in the next few years. Therefore, implementation of a proper water management system as well as preservation of existing surface and groundwater resources is essential to overcome this problem. A methodology is developed to find the most suitable locations for water harvesting structures in Hambantota District by using Geographic Information System (GIS) techniques. Suriyawewa Divisional Secretariat area is selected as the research area considering its average climatic conditions and location within Hambantota District. This methodology can be generalized to the whole District in the first instance. The research area is hydrologically analyzed to discretize the area into catchments and the preferred catchments to harvest the runoff based on surface area, slope and rainfall are found by using GIS techniques. The selected catchments are then analyzed with geological data and drainage characteristics to find the most suitable catchments to construct reservoirs to store rainwater. The analysis yields four such locations, which were subsequently field verified for spatial accuracy. However detailed local investigations are necessary before proceeding to actual construction of the reservoirs. Groundwater recharging also plays an important role in water management, as groundwater represents 30.1% of the world’s fresh water resources. GIS techniques are employed to integrate data on land use, climate, soil, stream pattern and ground slopes, and consequently to find potential areas for groundwater recharging. Here also, detailed local investigation must precede any construction work in the selected areas. Also, potential areas to implement roof water harvesting projects in Suriyawewa are found by analyzing the rainfall and building cover by using GIS techniques. These areas are recommended to be used as project areas when implementing efficient roof water harvesting methods. The methodology adopted here for Hambantota District can be used for water management in other Districts of the Dry Zone of Sri Lanka such as Monaragala, Puttalam, Ampara, Badulla and Kurunegala, as a solution for water stress conditions in those areas. An increment in water harvesting can significantly increase the crop yields in these areas and improve the economy as most of the Districts in the Dry Zone are agriculture-based. Also, a proper water management system is a must for the industrial development of the area under focus, while it gives a solution to the problems regarding drinking water. Proper water supply plays a major role in infrastructure development of these areas and would form the foundation for the overall development of the country.
- item: Thesis-AbstractFlow behavior of mineral particulates through conical silosRohitha, LPS; Fernando, WLW; Dissanayake, DMDOKSilo or Bin is used very widely in Mining, Processing, Pharmaceutical, Cement, Ceramics and Packaging industries. The purpose of the silo is to hold material until it is ready to use in subsequent processes such as processing, chemical, physical or transport. According to the Oxford Dictionary ( DK illustrated), a Silo is a pit or airtight structure in which green crops are kept for fodder or it can be a pit or a tower for the storage of grains ,cement etc, or it is an underground storage chamber for guided missiles. The capacity of a silo may vary from Kgs. to Tons. In this research, a silo is used as a conical shaped container with an orifice through which mineral sands of varying sizes were allowed to pass and their flow behavior were examined with respect to their material physical properties and silo parameters. In the first stage of the project, the flow behavior was studied using beach mineral sands with glass funnels with orifice diameters 3.5, 4.8 and 8.0 mm and heights 8, 10 and 24cm respectively to simulate silos of varying orifice. The capillary part of the funnels were cut uniformly at the neck regions to prepare them for the tests. It was decided to use naturally occurring geo-materials of different mineralogical, chemical, and physical characteristics for the investigation. For this purpose, samples of beach sand from several locations along the western coast of Sri Lanka were collected and sampled using the sampler riffler, thereafter sieved through 2mm sieve to remove sea shells and other extraneous impurities followed by spiral separation and tabling. Subsequently, magnetic separation and high tension separation were carried out to separate magnetic and non magnetic fractions according to the standard procedure. The fractions separated consisted of ilmenite, rutile, garnet and zircon. A sample of silica was also obtained from the glass sand deposit at Naththandiya. Each sand sample was sifted using the standard test sieves. Before conducting the flow properties of these minerals they were dried at 110°C for 2 hours and the test was conducted 3 times and the average flow rate obtained thus was plotted against the particle size and the diD ratio for each material. Where, d = average particle size diameter and, D = funnel orifice diameter. Interpretation of flow rate measurements and analysis of data indicate that all beach mineral sands used in the study had the same flow rate pattern. The mass flow rate vs diD curves consisted of three significant zones representing bridging effect, constant gradient zone with a negative gradient and the no-flow zone, which spilled over to the fine particle fractions. The effects of charge particle nature, moisture contained, repose angle, surface morphology of mineral and the orifice diameter of the funnel on the flow properties were also investigated. As the particles studied were naturally occurring, they were sub-angular having rounded edges. Another series of experiments were conducted using spherically shaped silica gel particles having diameters 1.2,2.2, and 3.3 mm respectively. In the second stage, a pilot plant in the form of a conical silo was fabricated in the workshop and the experiments were conducted using mineral samples each sample weighed approximately 3 to 6 kg. The samples for the second stage was obtained from two sources, Lanka Mineral Sands Ltd and the river sand pits at lngiriya. After a tedious process of size separation mostly involving sorting of particles of different size fractions by hand picking and sieving. The results obtained agree very closely with those obtained using the glass funnels. It is evident that there are three zones in the performance curve -flow rate vs particle size with the bridging effect region corresponding to diD ratios of 1/4 to 115 for relatively larger size particles and the region exhibiting the 'floc effect' resulting from residual charges in the fine sizes and air trapped within the floes. The mineral particles used were pre-dried (dried at 110°C for two hours).However, the presence of moisture in the powder seems to have a significant contribution on the flow rate. - The importance of the performance curve and its characteristic features have been discussed and also the relevance of the performance curve in designing silos.
- item: Thesis-AbstractDevelopment of conceptual geological model for the formation of hot water springs in Sri LankaPremasiri, HMR; Wijesekara, DS; Weerawarnakula, S; Puswewala, UGA; Abeysinghe, AMKBAs natures wonderful gift, several hot water springs occur in Sri Lanka though it does not fall within very active tectonic zone in the earth. They are mostly confined to the eastern sector of the island. However, hot water springs at Mahapelassa off Embilipitiya, Kanniyai off Trincomalee and Mahaoya are well known to people. These thermal springs show their out flow temperature ranging between 34°C to 56°C. The hottest springs lie at Kapurella (56°C), followed by Mahaoya (55°C), Marangala-Wahawa close to Padiyatalawa (42-45 ° C ), Mahapelassa (44-46 DC) and Nelumwewa, which was known earlier as Madawewa and now under a lake, records 45° C in mud samples (Fonseka 1994). The present research was aimed out mainly to model the formation of hot water springs in Sri Lanka based on geological and tectonic settings using geological, geophysical and Remote Sensing techniques while evaluating the hot water springs for their potential as energy resources or development as places for eco-tourism. Geological, structural and tectonic setting of the areas have been studied using geological, geochemical and geophysical techniques. Both field and libratory studies were carried out in order to compile geological and geophysical profiles and to determine geochemical and physical parameters of hot water springs in Sri Lanka. According to the results of this study, the major boundary between Highland Complex and Vijayan Complex show multiple thrust planes and shear zones showing imbrecated lithological slices of both Highland Complex and Vijayan Complex. Other than the ductile structures, brittle fractures, joints and fault planes extend as mega lineament for several kilometers. These lineaments produce good secondary aquifer conditions with adequate porosity. The surface mapping and geophysical evidence of the lineaments show that they are very deep and are interconnected. Therefore, they offer better pathways for surface water to percolate deep levels and return upwards with adequate pressure to reach the surface after heating. These structurally controlled hot water springs in Sri Lanka are associated with deep geologically weak zones of fracture or fault systems within the tectonically active thrust boundary. According to geochemical parameters and field evidence, hot water springs in Sri Lanka can be divided into three groups, Groupl: Mahapelassa Group 2: Kapurella, Mahaoya, Padiyatalwa , Palanoya and other around the Mahiyangana, Ampara and Group 3: Kannyai, Rathkhiriya and Adampane areas.). According to the chemical and physical parameters of hot water it can be concluded that Group (1) and Grou (3) are more suitable for therapeutic uses and have a good potential for development for eco-tourism. The Group (2) has hot water with low contaminations of salt, and show fairly high potential for generation of geothermal energy
- item: Thesis-AbstractDurability of rocks under tropical conditionsSamaradivakara, GVI; Dharmaratne, PGR; Puswewala, UGASri Lanka has a basement rock formation of metamorphic origin that the majority is gneissic type, which is intensively used in many of the civil engineering constructions. In addition, foundations of most of the important civil engineering structures are extended up to or into the fresh gneissic rock strata. Sri Lanka has a tropical climate. Therefore the study on durability of gneissic rocks under tropical conditions would be immensely beneficial to the construction industry of the country. The simulation of exact natural weathering conditions is quite complicated. This study concentrates mainly on how heat stress affects deterioration of index properties of gneissic rocks. When the rock mass gets heated, and cooled rapidly due to sudden rainfall, there is a possibility of propagating micro-fractures in the rock mass which will initiate weakening the strength properties of the rock mass. Most of the bridge abutments and dam constructions are associated with basement rock. In such locations rocks mass is alternately subjected to wetting and drying processes. Therefore the deterioration of rock resulting in its breakup, which is termed as "slaking" is also studied in this research. One hundred and sixty rock samples of gneissic rock of diameter 54mm (NX size) are tested in this research. Out of these 132 samples are fresh competent rocks and 28 are weathered to different degrees. These samples are selected from biotite gneiss and quartzo-feldspathic gneiss; the major two gneissic rock formations found in Sri Lanka. Fresh gneissic rock samples were subjected to heating and the weakening of their strength properties were studied upon cooling. Naturally weathered gneissic rock samples belonging to different weathering grades were also tested for their index properties. These were compared with the index properties of artificially weathered fresh gneissic rock samples and some correlations are established. The rate of deterioration of index properties of quartzo-feldspathic gneiss is seen to be more than that of biotite gneiss. Therefore more attention should be paid in the designing of foundations of important civil engineering structures in quartzo-feldspathic gneiss as far as the 'durability, is concerned, based on the project location..
- item: Thesis-AbstractHeat treatment of gems with special emphasis on geuda stonesPeiris, BPS; Dharmaratne, PGRDetailed literature survey is presented on gem minerals, corundum family of gems, colour in gem s tones and heat treatments. Physical and chemical investigations on gem minerals are conducted to understand the nature of treatable stones. Treatable stones are characterized by the presence of different types of impurities in the basic corundum structure. Optimum heating rates, cooling rates and soaking periods are established for geuda and ottu stones. Investigations carried out on over one thousand and twenty samples revealed that certain types of geuda stones can be converted into good blue sapphires while other varieties become light blue or dark blue stones. Removal of bluish and brownish tints in red geuda A comparative stones are not completely satisfactory. Study of the Lakmini furnace with the Toda furnace was carried out to ascertain the more economic one.
- item: Thesis-Full-textAssessment of rare earth element potential in different geological formations of Sri Lanka(2023) Batapola BDNM; Abeysinghe AMKB; Premasiri HMRIn recent years, the global demand for rare earth elements (REEs) has been burgeoning due to the wide range of applications in numerous modern and green energy technologies. Although China was dominating the REE market, now the reliance on Chinese REE production has begun to ease with the global attempts to explore new REE resources outside China. This growing global competition coupled with demand escalations provides an opportunity for developing countries like Sri Lanka to start explorations for new viable REE sources to become a potential REE supplier to the global REE market. Therefore, the present study focuses on assessing the REE potential in different geological formations in Sri Lanka based on their origins and occurrences. Accordingly, representative samples from the Eppawala phosphate deposit (EPD) (n=60), Ginigalpelessa serpentinite deposit (n=32), beach placers on the northeast coast (Verugal: n=18 and Pulmoddai: n=26) and the southwest coast (n=18), alluvial placers in the Walave river basin (n=20), granites at Thonigala (n=17), Massenna (n=10), Arangala (n=6), and Ambagaspitiya (n=6), and Ratthota pegmatite (n=6) were analyzed for their REE contents. Based on the results, the EPD, Massenna and Arangala granites, and Pulmoddai deposit were the most prospective REE sources in Sri Lanka. However, due to technological and environmental challenges associated with granitic occurrences and the Pulmoddai deposit when converting them into exploitable mineral reserves, the EPD was identified as the most prospective source in Sri Lanka in the present study. Despite the relatively low REO grade (~0.48% ΣREE2O3) in the EPD compared to other similar global occurrences, this deposit is significantly enriched in critical and highly demanded REEs like Nd, Pr, and Tb. Therefore, with upgraded extraction techniques, the EPD could become a potential diverse source of REEs that may contribute to maintaining a sustainable REE supply chain in the future.