Faculty of Engineering, Earth Resources Engineering

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item: Thesis-Full-text
Alternative phosphorus sources in lake bottom sediments around Eppawala phosphate deposit in Sri Lanka
(2018) Dushyantha MNP; Ratnayake N; Jayawardena CL
Jaya-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-Abstract
Applicability of phytoremediation methods to treat chromium contaminated waters
Hettiarachchi, MN; Karunarathne, S
Chromium 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-Full-text
Appraisal 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-text
Assessment of rare earth element potential in different geological formations of Sri Lanka
(2023) Batapola BDNM; Abeysinghe AMKB; Premasiri HMR
In 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.
item: Thesis-Abstract
Communicating data quality in a GIS environment
Thavalingam, K; Puswewala, UGA
The 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.
item: Thesis-Full-text
Comparative study of emulsion and water gel explosives for rock quarrying
Herath, B; Hemalal, VPA; Dhramarathna, PGR; Rohitha, LPS
In the mining field, blasting is the predominant method for breaking of consolidated rocks and the main objectives are to extract the large quantity at both minimum cost and having minimum damage to the environment. Rock breaking , over the years , which was limited to just breaking of boulders for the use of building and road construction has developed vastly to various aspects of mining namely ,open cast, underground and underwater blasting. Manually drilled single shot bore holes are disappearing and making way to multiple bore holes of immense depth with the introduction of the latest blasting technologies. Result of the introduction of optimum blasting techniques and sustainable development criteria, mining industry has twisted in the path of eco-friendly mining. Explosives and blasting techniques that are used nowadays are based on the above concept. Use of Dynamite changed to lesser powerful explosives such as Water Gel and then to Emulsion explosives. Our country also discarded the use of Dynamite several years ago and Water Gel explosives was introduced. Water Gel explosives is eco friendlier than Dynamite but could not be substituted in areas underground and underwater blasting. Introduction of Emulsion explosives was mainly to overcome these disadvantages of Water Gel Explosives. Aim of this study is to carry out a comparative study in all areas of open cast mining and to ascertain the most appropriate high explosive type for optimum output.
item: Thesis-Abstract
Development of a land use/cover monitoring system using satellite images
(2004) Jayakody, JAS; Puswewala, UGA
Remote 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-text
Development of a methodology to assess the geothermal energy potential in Sri Lanka
Nanayakkara, GD; Premasiri, HMR
Assessing 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-Abstract
Development of conceptual geological model for the formation of hot water springs in Sri Lanka
Premasiri, HMR; Wijesekara, DS; Weerawarnakula, S; Puswewala, UGA; Abeysinghe, AMKB
As 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-Abstract
Durability of rocks under tropical conditions
Samaradivakara, GVI; Dharmaratne, PGR; Puswewala, UGA
Sri 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..
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Effect of solids on a pinched sluice concentrator
Jeyadeva, B
The pinched sluice concentrator is a device for the separation of heavy minerals particularly beach sands. They come in a variety of size and shapes and have been extensively used in the beach industry, for over a century. But the basic mechanism involved in the specifications has not been fully understood. Most of the work up to 1982, had been empirical in nature. In 1983, an attempt was made to explain the behavior of a pinched sluice in items of established theories of fluid mechanics and mineral processing. However, their work was limited to particles o& single size. In the present analysis, an attempt has been made to refine the existing model, taking the effects of particle size and density into account. The relationship between the flow rate and depth of flow was confirmed and there, variation with particle size and feed concentration has been studied. A method has been developed to calculate the underflow flow rate of the sluice assuming logarithmic velocity distribution and the established relationship between Froude Number and the split height. Assuming that Bagnolds Shearing Theory holds in pinched sluice, operations, and also the dispersive pressure is some function of solid concentration, velocity gradient, specific gravity and diameter of the particles, a relationship was derived to predict the underflow pulp density. Above relationship was used to predict the grade of the underflow for a mixture of ilmenite and silica.
item: Thesis-Full-text
Effect of trenching on blast-induced ground vibration in sri lankan metal quarries
Samarakkody, SATI; Dharmarathne, PGR; Premasiri, HMR
Problems due to ground vibration are a matter of serious concern for the users of explosives. It is not possible to eliminate vibration completely or to contain them at the source. Effort need to be made in controlling them within safe level, without effecting the production schedules and economic viability of the project. When predicted or monitored vibration exceeded the statutory limit, ground vibrations are generally controlled by modifying the blast design parameters. In critical situation, digging a trench has reduced ground vibration. The extent to which it can reduce ground vibration has been examined by field experiments at a open cast quarry mine located at Arankele in Sri Lanka. After selecting a suitable quarry site at Arankale off Kurunagala in North-Western province of Sri Lanka. Suitable place for blasting face, digging a trench and observation point have been identified. Vibration measurement were carried out after single shot hole blasting method prior to digging a trench and after digging the trench with variation of depth of drill holes and depth ofthe trench, at points located just before the trench(A), just after the trench (B) and approximate observation point away from the trench (C). Average often single shot hole blast carried prior to digging trench show ground vibration reduction percentage are 6.326% ,1.23%, 7.023% and 18.309% at B, and 72.262%, 54.474%, 55.183%, and 45.191% at C. Results after digging the trench show ground vibration reduction percentages are 57.878%, 53.946%, 40.514% and 36.757% at B and 55.509%, 64.787%, 56.848% and 42.382% at C. Such results indicate, just after the dug trench, ground vibration reduction level is very much higher compared to the results obtained before digging the trench. However considerable deferences have not been observed at the observation point under same condition. The results also show that the percentage of the reduction depend on the trench depth to blast hole depth ratio.
item: Thesis-Full-text
Effectiveness of emulsion explosives in quarrying in high grade metamorphic rocks in Sri Lanka
(2017-06) Pathirana, KPR; Weerawarnakula, S; Hemalal, PVA
In mining, blasting is the predominant method adopted for breaking consolidated rocks with the main objectives being extraction of minerals at minimum cost with minimum damage to the environment. Explosive is a compound or a mixture of compound which is capable of undergoing extremely rapid decomposition with deflagration or detonation. When the explosive reaction takes place radial cracks are form by as a result of detonation pressure with fragmentations followed by gas pressure. The optimization of explosive usage in Sri Lankan metamorphic rock is the main objective of this research. The detonation velocity of the explosive should match, as closely as possible, the sonic velocity of the rock to be blasted of rock. The rock's sonic velocity is a reliable indicator of its structural integrity and resistance to fragmentation. With varying rock types, sonic velocities vary with varying structural formations. Aggregate impact value is one parameter of hardness of rock. This study is conducted by considering the aggregate impact value as the indicator of hardness of rock. Test is planned, keeping blasting parameters constant namely hole diameter, explosives charge, burden, spacing and stemming against the different rock types with different aggregate impact values. The efficient use of explosives, along with the proper selection, will be the key to a successful blasting program. After comparison of the results of production rock volume and fragmentation formulate the explosives usage to get the optimum results that how explosives behave with the different rock types with different aggregate impact values or hardness. Dautrich method is the first time practically used in Sri Lankan field to determine the velocity of detonation of emulsion explosives in this research. This method is indirect field test method for suggesting VOD of explosives and the determination of the VOD is based on the fact that processes that propagate at different linear velocities travel different distance, in the same time interval. According to the blast results harder rocks fragmented with emulsion explosives, higher production volume were obtained than less hardness rocks. Increasing the hardness, increasing the production rock volume. Therefore, the relationship with hardness of rock and emulsion explosives usage is observed. Fly rock throw is more important to safety of blasting. This research indicates that fly rock distance is higher with AIV values more than 27. This result clearly indicates that emulsion explosives is very suitable for Sri Lankan metamorphic hard rocks.
item: Thesis-Full-text
Enhancing physical properties of recycled aggregates with rice husk ash-cement mixture
Kariapper, A.B.Y.; Karunarathne, S; Nanayakkara, D
The 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.
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Flow behavior of mineral particulates through conical silos
Rohitha, LPS; Fernando, WLW; Dissanayake, DMDOK
Silo 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.
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Heat treatment of gems with special emphasis on geuda stones
Peiris, BPS; Dharmaratne, PGR
Detailed 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.
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Identification of rock weathering by conventional methods and image analysis techniques
(2023) Kanagasundaram, G; Dassanayake, ABN; Jenaayawardna, CL; Chaminda, SP
Observations 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
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Influence of mechanical and aggregate properties of rock on powder factor in rock blasting
Karunanayake, KDP; Dharmaratne, PGR; Rohitha, LPS
Quarry metal is a widely used material in any large scale construction industry. Though demand for quarry metal substantially increased due to recently emerged large infrastructure development projects in Sri Lanka such as highway and port city, profit margins of the quarrying has drastically reduced due to high powder factors recorded in recent rock blasting activities of local quarries. Most possible reason for realizing high powder factors could be the introduction of various new explosive agents such as water-gel in to the local mining industry. Importance of analysing the influence of mechanical and aggregate rock properties on powder factor arises in this context to allow seeking suitable rocks those incur minimum blasting expenditure during the production stage. Outcomes of the project can be used to predict powder factor which could be achieved in blasting operations of a certain rock even before starting the quarry operations to minimize its production cost in the long run. Eight quarries operates under the close supervision of qualified Mining Engineers were selected for this study to ensure blasting geometry and configurations have being properly managed during the realized powder factor data recorded time period. Random core samples were obtained from each quarry site and they were tested for Density, Uniaxial Compressive Strength (UCS) and Tensile Strength. Similarly, random aggregate samples were taken and performed the Aggregate Impact Value (AIV) test. Rock Mass Rating (RMR) was determined for each quarry using UCS values and other field data obtained at the site. Explosive consumption and drilling records for recent six month were obtained from each quarry for the calculation of powder factor. Powder factor was plotted against each selected rock property and regression analysis was performed on test results to understand their standalone influence. The only realized best fitting model for the Powder Factor was AIV according to the regression analysis and it is very closely following the quadratic model. Rock property test results and past records of few other quarries were used to validate formulae obtained in this research. Explosive cost and production cost of all the quarries analysed for the same six months period. Results revealed that the production cost is a function of explosive cost since other costs on drilling, machineries and labour are usually incur relatively fixed costs in nature. Hence it can be concluded that the aggregate rock properties, especially Aggregate Impact Value (AIV) influence on powder factor of blasting and furthermore affects economics of the quarry production. More importantly, combined formula derived in this research can be used predicting powder factor of a fresh rock before conducting any blasting activity.
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Insights into the heterogeneity of coal fly ash waste
(2024) Kanesalingam, B; Jayawardena CL; Fernando A; Amarasinghe DAS; Attygalle D
Coal 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
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Investigation of the possibility of converting seawater to drinking water in Hambantota area by reverse osmosis
Illangakoon, UI; Dissanayake, DMDOK; Walpolage, S
Habantota 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%.