Browsing by Author "Rathnayake, NP"

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Alternative for river sand
(Department of Earth Resources Engineering, 2007-11) Ekanayaka, EMTM; Jayawardene, MN; Kannangara, KKDM; Puswewala, UGA; Rathnayake, NP; Chaminda, SP; Vijitha, AVP; Karunaratne, S
The need of finding an alternative for river sand arises due to the over exploitation of river sand and its various harmful consequences. The focus of the current study was on offshore sand, which is clearly one of the most viable alternatives for river sand, with respect to availability, ease of extraction, environmental impact and cost. Offshore sand is already used in Sri Lanka mainly for road filling and it is also used for construction in all over the world. A sea survey was conducted in Kaluthara-Benthota sea area and a resource distribution map was plotted. Samples from Muthurajawela offshore sand stick piles were collected and CT content was checked. Offshore sand saturated with sea water has Cl' content around 0.3%, where as if the seawater is gravity drained; it reduced to around the acceptable 0.075%. The action of an average rain fall would be enough to reduce the CT contents to below acceptable levels. However, two other alternatives were also studied in a limited way, namely manufactured sand and quarry dust are quarry products. While quarry dust is merely a by product from the production of course aggregate and tends to be flaky in shape, manufacture sand is actually produced such that a more desirable "rounded cubic" shape is obtained.
item: Conference-Full-text
Application of simulation methods to understand tsunami processes around the coastal region of Sri Lanka
(Department of Earth Resources Engineering, 2007-11) Rathnayake, RMMT; Nilminie, WNRPN; Senanayake, DS; Rathnayake, NP; Karunaratne, S
Tsunami is one of the most devastating natural disasters which cannot be prevented or precisely predicted even with the modern advanced technology. One of the best solutions for prediction as well as for the risk analysis of this natural disaster is Numerical Modelling. Present study focuses on the generation of earthquake induced different Tsunami scenarios from the potentially high amplitude earthquake generation zones in the Indian Ocean using Tsunami numerical modelling. Simulation modelling for different scenarios was carried out for source, propagation and inundation using UNESCO/IOC recommended interfaces of AVI NAMI and ComMIT, which uses TUNAMI N2 model. Etopo 2, JEBCO (combine SRTM, ETOP2 and Sea Map data) were used for bathymetry analysis. Distribution of wave heights, run up heights for given locations and arrival times of the waves were simulated as output data. Different Tsunamis were simulated, taking Java Sumathra and Macrum zones as Tsunami sources. Wave heights and propagation of Tsunami waves around twelve locations of Sri Lanka were analysed and vulnerable areas for different scenarios were identified. Results further indicated that if a Tsunami is triggered at Java-Sumatra, Southern part of Sri- Lanka will be severely affected, and particularly the Yala region, because of the direct hit of the Tsunami waves. ComMIT simulation results showed strong coupling to Tsunami sediment data and actual tidal records for 26th December 2004 Tsunami. Therefore, ComMIT seems to be one of the best models for Tsunami warning and forecasting in Sri Lanka.
item: Conference-Full-text
Characterization of tsunami wave using texture & structure of sediments from South Western coast of Sri Lanka
(Department of Earth Resources Engineering, 2006-10) De Silva, RHSI; Jeyram, P; Perera, RSL; Thananchayan, A; Wickramanayake, NU; Rathnayake, NP; Premasiri, HMR; Abesinghe, AMKB; Puswewala, UGA; Karunaratne, S; Dissanayake, DMDOK; Ratnayake, N; Chaminda, SP
This research focuses on characterization of Tsunami waves by using tsunami sediments, as the only reliable source of information which a Tsunami leaves after strike are sediments. The sediments contain information about Tsunami waves which can be extracted by analyzing. The study focuses on evaluating wave height, flow velocity and wave energy by examining of the thickness, grain size distribution, sediment structures and texture of tsunami deposits. These findings can be used for the prediction of Tsunami threats and in the formulation of precautionary measurements.
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Coastal erosion in South Western part of Sri Lanka from December 2006 to June 2007
(Department of Earth Resources Engineering, 2007-11) Hansi, MKTN; Lokukankanamage, DMG; Ranasinghe, GP; Witharana, GH; Rathnayake, NP; Karunaratne, S
Coastal region is a very valuable area for developing countries like Sri Lanka, since a good protected coastal region will facilitate the tourism as well as fishing Industry. But the coastal erosion, especially in South Western parts of Sri Lanka has significantly destroyed the coastal land. Therefore, effective management of the coastal area has become a necessity. Present study is focussed on the variation of coastal profile at ten selected locations from Moratuwa to Balapitya and the monthly changes of beach width, profile and the grain size distribution of sediment at the mean sea level. The study was conducted from December 2006 to June 2007. Results showed that during North East monsoon, the beach face became wider and gentler whereas, during South West monsoon the beach face became narrower and steeper. Further, the mean grain size showed higher values during North East monsoon period than South Western monsoon. This variation of beach width, beach profile and the sediment grain size was strongly correlated with the rainfall changes and it was concluded that the coastal erosion in this area is directly controlled by monsoon changes.
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Determining the characteristics of the calcite intrusions in the southern part of eppawala deposit and its applicability for the industries
(Department of Earth Resources Engineering, University of Moratuwa, Sri Lanka, 2022-12-23) Peter, GKMR; Sivaruban, S; Jayathilaka, GMANGNMB; Lasantha, MML; Rathnayake, NP; Hemalal, PVA; Batapola, BDNM; Jayawardena, CL
Eppawala is the only phosphate deposit that is currently being mined in Sri Lanka and is composed of mainly two parts northern and southern. The ongoing phosphate mining process in the southern part has resulted in the exposure of fresh carbonatite embedded with large apatite crystals and those intrusions need to be removed before continuing further phosphate mining in that area. Therefore, we need to address a suitable method to use those calcite intrusions properly. In this paper, we are discussing the characteristics of calcite matrix such as critical anions (fluoride, chloride), P2O5 content, heavy metals, oxides, and the suitability of applying those removing calcite boulders for further industries including the fertilizer industry. Ion selectivity, titration, colorimetry, and induced coupled plasma spectrophotometry were used for analyzing the characteristics respectively for fifteen samples from three different boulders in the southern part. Results from critical anions and heavy metal percentages proved the absence of toxicity in calcite matrix and oxides percentages showed that it can be applied directly in its natural form only for the fertilizer industry by a quantitative comparison whereas upgrading processes need to be implemented to meet the specifications in other industries.
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Exploration of ilmenite potential in and around Kalu and Benthara river mouths with special reference to the variation of TiO2 content along a selected strech of Kalu Ganga
(Department of Earth Resources Engineering, 2006-10) Kumara, HANHM; Medagoda, CJ; Sivakala, S; Sugaraj, K; Wickrama, MADMG; Vijitha, AVP; Dissanayake, DMDOK; Rathnayake, NP; Karunaratne, S; Dissanayake, DMDOK; Ratnayake, N; Chaminda, SP
Although Ilmanite, Rutil, Zircon and Monazite occurs in beach sand of Sri Lanka, the sufficiently concentrated deposits for economic exploitation have been only identified yet in and around Pulmoddai, Baruwala and Kudremalai beaches. Of these, Pulmoddai is the largest beach sand deposit ever found in Sri Lanka, which is estimated to contain nearly, 4,000,000 tons of raw sand. However it has been noticed that beach mineral sand occurrence in many other parts of the country and detail investigation has not been carried out yet in those areas. Exploitation has been carried out only in Pulmoddai which is located near the rebels control areas. Since 1998 with production coming to a stand still, the Pulmoddai plant which a government own company is confined to selling its existing stockpile with Zircon and Rutile being bagged and transported to Colombo and exported. Therefore finding an alternative source to supply the demand of the export market to earn foreign exchange is a prior necessity of the country. Therefore this study was carried out to identify ilmenite potential in and around Kalu and Benthara river mouths and investigation has been carried out to identify the variation of Ti02 content in ilmenite along the Kalu Ganga track by sand sediment analysis. Gravity and the magnetic separation processes were employed for the processing of the sand samples. Results show that the particle size of Ilmenite in both river mouths deposits were reported in the range of+ l25J.lIl1to +250~tm sizeand this may mainly depend on grain size, flow velocity of the river, distance travel as well as energy of the sea waves. Variation of the titanium content in ilmenite along the Kalu Ganga can be concluded may due to the replacement of Fe in Ilmenite with another foreign element available in the river.
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Impacts of salt water intrusion on construction aggregates of 'Kalu ganga' estuary
(Department of Earth Resources Engineering, 2009-05) Silva, KBA; Kumara, IGIK; Rathnayake, NP; Karunaratne, S
'Kalu Ganga' is one of the main suppliers of river sand (113,360 cubes per year) in the country. Due to the continuation of sand mining, salt water intrusion has been increased over the years. The focus of the current research is to understand impacts of salt water intrusion on river sand and to understand whether the absolute chloride content of mined sand is within permissible level (0.075% Cl ) for the construction purposes. Two surveys were conducted along 'Kalu Ganga' estuary (10 km from river mouth) in predetermined intervals to measure depth, conductivity profiles and to collect sediments samples. Survey dates (16/12/2008 and 12/03/2009) were selected considering the maximum difference of tide and rain fall. The sand samples were analysed for Cl' content. Results showed significant salt water intrusion even during dry season («2300 pS/cm). All measured conductivity values were similar to the conductivity levels observed at the sea mouth. But during dry season the Cl- content of sediments is relatively high at river mouth. However, during rainy season, measured salt water intrusion levels were dropped down remarkably («200 pS/cm) and even at the sea mouth, sediment samples showed significant low values of absolute Cl* content (0.0176%). Therefore, it is recommended to extract sand from 0.5km from the sea mouth only during rainy season. This will also control the flooding in Kaluthara area. However, further studies are necessary for understanding other environmental effects of river sand mining near the sea mouth.
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Impacts of salt water intrusion on construction aggregates of 'Kalu Ganga' estuary
(2014-08-08) Silva, KBA; Kumara, IGIK; Rathnayake, NP
'Kalu Ganga' is one of the main suppliers of river sand (113,360 cubes per year) in the country. Due to the continuation of sand mining, salt water intrusion has been increased over the years. The focus of the current research is to understand impacts of salt water intrusion on river sand and to understand whether the absolute chloride content of mined sand is within permissible level (0.075% Cl-) for the construction purposes. Two surveys were conducted along 'Kalu Ganga' estuary (10 km from river mouth) in predetermined intervals to measure depth, conductivity profiles and to collect sediments samples. Survey dates (16/12/2008 and 12/03/2009) were selected considering the maximum difference of tide and rain fall. The sand samples were ana lysed for Ct- content. Results showed significant salt water intrusion even during dry season ("'2300 IlS/ cm). All measured conductivity values were similar to the conductivity levels observed at the sea mouth. But du:ring dry season the CI- content of sediments is relatively high at river mouth. However, during rainy season, measured salt water intrusion levels were dropped down remarkably ("'200 IlS/ cm) and even at the sea mouth, sediment samples showed significant low values of absolute Cl- content (0.0176%). Therefore, it is recommended to extract sand from O.5km from the sea mouth only during rainy season. This will also control the flooding in Kaluthara area. However, further studies are necessary for understanding other environmental effects of river sand mining near the sea mouth.
item: Conference-Full-text
Offshore sand exploration around Kaluthara-Beruwala area
(Department of Earth Resources Engineering, 2007-11) Gunasinghe, AWDC; Chandana, NHS; Ranaweera, DHD; Vijitha, AVP; Rathnayake, NP; Karunaratne, S
Offshore minerals are used as a raw mineral for various types of industries around the world. The exclusive economic zone belonging to Sri Lanka more than eight times land area of the country, offering huge potential for extraction and exploitation of minerals. Industrial sector, including mining and minerals, should grow to achieve the development of the country. Therefore this study was carried out to investigate the offshore sand mineral potential around Kaluthara — Beruwela area. About 200 samples were collected from sea floor, from a grid of 500m, 1000m Easting and Northing respectively. Investigation was carried out to identify the variation of particle size and mineral content around the Kaluthara area by sieve analysis. For each sample, particle size distribution curves were plotted and mean particle sizes, sorting and skewness were obtained. Heavy mineral content was also determined using gravity separation, magnetic separation; high tension separation and microscopic observation. Resource maps were plotted and mineral resources areas were demarcated.
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Operational hydrodynamic numerical model covering Sri Lanka waters
(2014-08-08) Girihagama, RWRHMRLNK; Dissanayake, DMSS; Wijerathne, EMS; Rathnayake, NP
As a part of ongoing project on development of operational hydrodynamic model covering Sri Lanka Waters and Northern Indian Ocean (67.5- 99.5 E and 1.5 S to 24.5 N), we employed a Princeton Ocean Model, NOAA (POM 08) to simulate wind driven circulation, sea surface topography, sea level setup, upwelling and possible storm surge conditions. The JEBCO0.5 min bathymetry was interpolated to generate high resolution horizontal and vertical grid domain. For the model initial salinity and temperature data were extracted from World Ocean Atlas 2005 (WOA '05). Seasonal wind driven circulation simulations were carried out by forcing monthly mean NCEP climatologically winds. Experimental model runs were carried out with different wind speeds and directions to examine the possible storm surge conditions. The model runs with SW winds reveals significant sea level setup on the Bangladesh coast. The model results of SSH are compared with observational data from the TOPEX altimeter. The model successfully captures many of the important circulation features observed in the region. This includes the reversing wind driven circulation, upwelling off south of Sri Lanka during SW monsoon, strong currents south of Sri Lanka. The long term goal of this project is the establishment of an operational hydrodynamic model to forecast physical process including storm surge conditions covering Sri Lanka Waters and Northern Indian Ocean.
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A pilot study on the mineralogical and geochemical characteristics of a recently discovered in-situ beryl occurrence at Kaltota, South Central Sri Lanka
(Department of Earth Resources Engineering, 2007-11) De Silva, PJS; Kuhananthan, P; Consalas, MA; Nazlan, MZM; Afal, MCM; Abeysinghe, AMKB; Rathnayake, NP; Weerawarnakula, S; Premasiri, HMR; Siriwardana, CHER; Karunaratne, S
Recently discovered in-situ beryl occurrence at Kaltota, southcentral Sri Lanka was studied by a pilot study of soil survey to probe its mineralogical and geochemical characteristics. Overall mineralization of the occurrence comprises of beryl, garnet, tourmaline, quartz, topaz and zircon. Beryl and tourmaline occur mainly as scattered detrital grains and as gravity-enriched elluvial concentrations within the overburden. Geological evidences suggest subsurface extension of the mineralization in host pegmatite and in contact zone. Total of 18 soil samples were collected from a preplanned grid within the site and, mineralogical analysis was performed on the panned heavy mineral concentrates of soils. In chemical analysis, soil samples were treated with both aqua regia digestion and alkali fusion method followed by Atomic Absorption Spectrometry (AAS). With the better results, alkali fusion method was chosen to obtain be concentrations in the soils. The results of the mineralogical analyses shows an existence of beryl and other gem minerals in different proportions in the heavy concentrates, which are in comparison with the anomalous Be concentrations found in the chemical analyses of soils. The results are to be further examined by a detailed study, probably followed by drilling to elucidate subsurface distribution of the mineralization.
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Prospecting geothermal energy from hot water springs at Padiyathalawa
(Department of Earth Resources Engineering, 2006-10) Anitha, SSS; Chanaka, HGDD; Dassanayake, ABN; Wanni Arachchi, WADSR; Suthakar, AA; Abeysinghe, AMKB; Premasiri, HMR; Rathnayake, NP; Dissanayake, DMDOK; Karunaratne, S; Dissanayake, DMDOK; Ratnayake, N; Chaminda, SP
Being a country with an increasing population, the demand for power is also increased in Sri Lanka As a result there will be a power crisis in the country near future. In this scenario we can not totally depend on the conventional power sources. It is timely to find out alternative cleaner energy sources. Geothermal is a prominent energy source which can produce uninterrupted power supply. Thermal springs of Sri Lanka are a manifestation of the earth's internal heat, and this tremendous potential of geothermal energy is not yet fully investigated for vast range of applications mainly for power generation. This research project mainly focused on assessing the feasibility ofPadiyathalawa hot springs to produced geothermal energy. Mainly geophysical and geochemical explorations were carried out along the target area to locate the fracture pattern and the sources of hot springs. As a conclusion, feasibility study indicates that the all hot water springs are originates at a single source and zone having high fracture density has been identified which is suitable for further investigations. Also two locations have been identified for produce energy combining with another technology using the water having out flow temperature of 44°C.
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Replenishment dynamics at Verugal beach heavy mineral deposit
(Department of Earth Resources Engineering, 2014-07) Dissanayake, DMCJB; Igalawithana, TD; Karunarathne, AVPI; Maduranga, SWM; Udayakumara, PWG; Amalan, K; Rathnayake, NP
Eastern coast of Sri Lanka is abundant with heavy minerals, particularly at Pullmuddai where Sri Lanka's only heavy mineral processing plant is situated. Verugal is one other areas where there is a rich, heavy mineral deposit that has the potential to be exploited.Heavy mineral beach sand deposits are dynamic in which the composition and the amount of reserves vary with time due to changes in coastal waves and currents. Therefore, a proper understanding of the replenishment dynamics is required to develop a comprehensive mine plan for the extraction of heavy mineral sand. This study focuses on the understanding replenishment mechanism at Verugal Beach Heavy Mineral Deposit. Samples from test pits were collected along the transect perpendicular to the beach at approximately 500 m interval from visible deposit at Verugal area representing bothsouthwestern monsoon and northwestern monsoon. Collected samples were subjected to sieve analysis to understand the grain size distribution and grain counting through reflected microscope to understand the heavy mineral concentration. Variations in deposit dimensions with seasonal weather changes along withspecific heavy mineral concentrations and replenishment rates can be used to develop a proper mining plan to commence sustainable extraction.
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Replenishment Mechanism atVerugal Beach Heavy Mineral Deposit
(2015-08-14) Dissanayake, DMCJB; Igalawithana, TD; Karunarathne, AVPI; Maduranga, SWM; Udayakumara, PWG; Amalan, K; Rathnayake, NP
Eastern coast of Sri Lanka is abundant with heavy minerals, particularly at Pullmuddai where Sri Lanka’s only heavy mineral processing plant is situated. Verugal is one other areas where there is a rich, heavy mineral deposit that has the potential to be exploited.Heavy mineral beach sand deposits are dynamic in which the composition and the amount of reserves vary with time due to changes in coastal waves and currents. Therefore, a proper understanding of the replenishment dynamics is required to develop a comprehensive mine plan for the extraction of heavy mineral sand. This study focuses on the understanding replenishment mechanism at Verugal Beach Heavy Mineral Deposit. Samples from test pits were collected along the transect perpendicular to the beach at approximately 500 m interval from visible deposit at Verugal area representing bothsouthwestern monsoon and northwestern monsoon. Collected samples were subjected to sieve analysis to understand the grain size distribution and grain counting through reflected microscope to understand the heavy mineral concentration. Variations in deposit dimensions with seasonal weather changes along withspecific heavy mineral concentrations andreplenishment rates can be used to develop a proper mining plan to commence sustainable extraction.
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Seasonal changes and coastal erosion in the South Western part of Sri Lanka
(2008-05) Subramaniam, DN; Amarakoon, GGNN; Gunathunga, SGAS; Pathinayaka, RC; Indeewara, VGD; Vijitha, AVP; Rathnayake, NP; Karunaratne, S
Sri Lanka is an Island, the economy of which relies very much on the developments of the coastal region, which supports tourism and fisheries. In addition, especially in the South-Western part of the country, the infrastructure lays in the proximity to the coast and the land is more precious and valuable. Further, the constructions around the coastal expanse, alter the sand dynamics of the coastal belt, increasing erosion and deposition at specific points. The erosion cannot be identified at a glance in one day, but when considering long-term sustainable developments, the loss of expanse due to erosion becomes vital. Hence, in this study we analysed the erosion pattern and gross land loss along South-Western part of Sri Lanka, considering duration of 6 months (Jun/07 till Jan/08). The variations of beach profile were determined from leveling perpendicular to the beach at 10 predetermined locations at one month interval. Grain size variations were also analysed from the samples collected from the mean sea level from each sampling locations. A strong correlation was observed at this location between the monsoon and erosion, while at Egodauyana, Panadura Moya, kani Lanka hotel and Payagala revealed rapid changes in erosion/deposition. Although the rainfall influences the beach variation, longshore currents, tides and coastal features (natural and artificial) are found to be dominating at these locations.