Browsing by Author "Iresha, H"

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item: Conference-Full-text
Analysis of subsurface strata of Colombo and Gampaha districts of Sri Lanka, based on geotechnical investigation data
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Karunarathna, K.S.S.; Wasana, N.W.A.P.; Bandara, M.G.K.M.; Ranathunga, R.M.IG.N.K.; Samaradivakara, G.V.I.; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
The subsurface exploration for geotechnical engineering applications in Sri Lanka is mainly based on borehole investigations. Several leading geotechnical engineering companies in the country have already done more than a couple of thousands of subsurface investigations for small- and large-scale civil engineering projects. Even though project-wise subsurface information is available, integration of available subsurface data in proximity, and development of subsurface three-dimensional (3D) models can hardly be seen in the country. This has been a significant disadvantage in the cost and planning of large-scale new investigation projects. Due to lack of information, most of the projects start even without knowing the tentative bedrock level of the area. Hence, in investigation cost estimations, pricing for most of the items is recorded as “rate-only”, hence the total cost could immensely be higher than the available budget with the client. However, if 3D modelling of subsurface strata can be done area-wise, based on already available borehole data, such uncertainties could be minimized. In this research, more than a thousand subsurface investigation reports were reviewed; data were recorded and analysed targeting to interpret the subsurface of the western province of Sri Lanka, and to develop a 3D subsurface model for the same. However, scattered data had to be excluded in data analysis, and eventually, the study was confined to Colombo and Gampaha districts, in which more than sufficient data could be found. By using interpolation methods, surface strata were interpreted in between borehole locations by matching similar geological features. In addition, artificial neural networks were used to forecast borehole data in exceptional cases for a few locations. This helped to improve the spatial coverage and accuracy of the 3D model developed by means of “Surfer” software. The 3D model developed for the study area well demonstrates the subsurface strata and facilitates taking of cross sections in any direction within minutes. Hence, the findings of this research will enhance the outcome of general geotechnical investigation practice in Sri Lanka. This will also be immensely beneficial in planning and budgeting of future large-scale geotechnical investigation projects, more accurately than in the past, saving energy and time.
item: Conference-Full-text
Assessing the influence of microstructural features on deformation of rocks under triaxial loading
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Silva, SAV; Rathnapriya, RHDL; Riyasath, MSM; Dassanayake, ABN; Fujii., Y; Wickrama, MADMG; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Assessing the influence of microstructural features on the deformation of rocks under triaxial loading is vital in rock engineering applications, aiding safe and efficient operations by predicting the deformation of rocks. Triaxial testing offers the simulation of stress conditions within a rock to examine the deformation of rocks with confinements. This research focuses on how microstructural features, such as cementing material and pore geometry, affect the deformation behaviour of rocks subjected to triaxial loading. Two rock types were considered in this study: Kimachi sandstone (medium hard clastic rock) and Bibai sandstone (hard clastic rock). The progressive failure behaviour under Hydro Mechanical (HM) coupling effect was analysed by stress-strain distribution and the fracture geometry was examined using CT images of the specimens which were tested under different confinements. Thin sections were analysed to examine the changes in porosity and the effect on the cementing material with the confinement. The results of the proposed approach reveal a clear influence of the effective confinement on the failure of rocks and how it influences the porosity and cementing material of rocks. It is found that the Bibai sandstone shows a brittle failure and a shearing deformation while Kimachi sandstone shows a brittle to ductile failure and shearing to compaction deformation with the confinement due to the less presence of cementing material within Bibai sandstone compared to Kimachi sandstone. Therefore, with the confinement, the porosity of Bibai sandstone increases while it decreases in Kimachi sandstone. The results highlight the differences in the failure mechanism of a particular rock type for the same effective confinement which is a result of only a partial contribution of the pore pressure on the failure. These findings provide valuable insight into the assessment of microstructural features on the deformation of rocks under triaxial loading, aiding in the development of safer and more efficient rock engineering operations.
item: Conference-Abstract
Comparison of critical metal potential in beach and offshore sediments of Pulmoddai, Sri Lanka
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Nanayakkara, C.J.; Ratnayake, N.P.; Premasiri, H.M.R.; Abeysinghe, A.M.K.B.; Ratnayake, A.S.; Dushyantha, N.P.; Batapola, N.M.; Dilshara, R.M.P.; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
The global transition towards renewable energy resources for power generation has increased the demand for critical metals (CMs), including rare earth elements (REEs). This rapid growth of demand coupled with geological scarcity and geo-political concerns has posed great challenges in securing the supply chain of CMs. Therefore, prospecting new CM sources worldwide is of timely importance. In this context, the Pulmoddai coastal stretch in Sri Lanka has been recognized as a dynamic deposit with established potential for REEs and other critical metal resources, currently undergoing beach face mining operations. The focus of this study is to compare the critical metal potential in the beach and offshore sediments in Pulmoddai, Sri Lanka, crucial for determining the origin and delineating the extent of this deposit. Twelve onshore and nineteen offshore samples were collected and analyzed for CMs (V, Cr, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, and Cs) and REEs. Based on the results, light REE content (LREE), heavy REE content (HREE), and total REE content (TREE) were computed for both onshore and offshore locations. For onshore sites, LREE, HREE, and TREE ranged respectively from 43.27 to 244.09 ppm, 19.62 to 92.29 ppm, and 62.92 to 336.39 ppm. Conversely, offshore locations exhibited higher concentrations with the corresponding values ranging from 116.12 to 363.62 ppm, 8.57 to 120.93 ppm, and 167.93 to 484.55 ppm. Sr, Ni, and Cr were determined as the most abundant CMs for both onshore and offshore locations. Sr, Ni, and Cr concentrations ranged from 227.17 to 674.58 ppm, 116.17 to 675.88 ppm, and 43.55 to 112.87 ppm respectively for the onshore locations. The corresponding ranges for offshore sites were determined as 370.86-754.30 ppm, 235.43-721.44 ppm, and 32.51-172.62 ppm. The higher CM content in offshore regions suggests an offshore origin to this dynamic deposit, which is enriched by the offshore sediments transported onshore and deposited on a long-term basis. Therefore, regulatory authorities overseeing the mining operations of Pulmoddai deposit should accurately delineate its extent, integrating both onshore and offshore regions as a unified system, rather than solely focusing on prospecting the longshore areas.
item: Conference-Abstract
Development of a numerical simulation method for complex fracture process of rocks based on 3-D ECZM-FDEM using GPGPU parallel computation
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Takarada, K; Fukuda, D; Di, W; Liu, H; Ogata, S; Maeda, Y; Min, G; Kawasaki, S; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
For the developments of surface and underground mines, numerical simulation has been regarded as a highly crucial approach in terms of mining design and safety. The combined finite-discrete element method (FDEM)[1] has attracted significant attention for reasonably simulating very complex fracture processes of rocks. FDEM is based on the continuum mechanics model considering finite-strain theory, the cohesive zone model (CZM)[2] by utilizing initially zero-thickness cohesive elements (CEs) and potential-based contact mechanics model. The FDEM based on the intrinsic CZM (ICZM), which inserts the CEs at the onset of the simulation, has been the mainstream of previous studies applying FDEM due to its simpler implementation. Although the FDEM is generally known as a computationally expensive numerical method for both two-dimensional (2D) and three-dimensional (3D) problems, the computational acceleration of the ICZM-based FDEM can be achieved with relative ease through parallel computation using general-purpose graphics processing units (GPGPUs). However, the accuracy of continuous deformation when rock is intact is significantly compromised in the ICZM. The FDEM based on the extrinsic CZM (ECZM), which activates CEs only when and where the local stress reaches the given activation criteria, is expected to overcome this issue. However, although the implementation of 2-D ECZM-based FDEM with the GPGPU parallel computation has been reported, its 3-D counterpart has not been achieved. Based on this background, this study proposes a novel master-slave algorithm to achieve the implementation of the GPGPU-parallelized 3-D ECZM-based FDEM. Figure 1 shows the examples results of GPGPU-parallelized 3-D ECZM-based FDEM for uniaxial compression test simulation and spalling test simulation [3]. These results indicate that the developed ECZM-FDEM can reasonably reproduce the fracture and failure patterns of rocks in both static and dynamic tests compared to laboratory tests. The significant advantage of the proposed approach lies in the fact that the precision of continuous deformation can compared to those of the parallelized ICZM-based FDEM. The proposed approach could be an important basis for the further developments of the ECZM-based 3-D FDEM for simulating very complex 3-D rock fracturing processes in the various rock engineering problems.
item: Conference-Abstract
Disaster and attitudinal vulnerability: a systematic conceptual review
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Senavirathna, C; Rajapaksha, S; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Natural hazards represent a destructive force that poses a significant risk to human life, property, and the economy, among other aspects. The impact of natural hazards on the economy and human populations is profound. Various attitudes, beliefs, and behaviors are linked to different demographic groups, some of which may be more susceptible to these hazards than others. In developing nations, catastrophic natural events like tsunamis can deliver a sudden blow to their development trajectory, leading to a costly and challenging recovery process. A key contemporary challenge in disaster preparedness involves the effective application of soft measures, focusing on assessing local awareness, knowledge, perception, and attitudes towards disasters. The primary research inquiry in this investigation pertains to understanding the existing knowledge surrounding attitudinal vulnerability to disasters. The aims of this study include conducting an extensive review of current knowledge on attitudinal vulnerability in disasters and identifying potential avenues for future research.PRISMA framework and guidelines have been followed to conduct this systematic conceptual review. Total of 128 articles were initially identified from the Scopus database using the key words “Disaster”, “Vulnerability” and “attitude”. Review protocol has been developed according to the PRISMA guidelines. Analysis method used in this study was keyword co-occurrence utilizing the VOSviewer software (Version 1.6.20). The principal discoveries of this theoretical manuscript encompass the delineation of forthcoming avenues for research and areas of research deficiency, such as knowledge lacunae, empirical deficiencies, contextual deficiencies, and methodological deficiencies. A comprehensive framework is imperative to grasp the extent of the matter, encompassing both the technical and social repercussions. Subsequent research endeavours should concentrate on the amalgamation of Blockchain and the internet of things to facilitate real-time data utilization in the realm of disaster readiness. Initiatives aimed at enhancing disaster preparedness should specifically target younger demographics for enhancement purposes. In conclusion, the influence of past experiences on current and future preparedness needs to be explored enhancing public attitudes and knowledge of climate change and disaster risk
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Distillery spent wash as an alternative fuel in boilers and potash recovery from that ash remaining in boilers
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Warnakulasooriya, G.A.P.K.G.G.; Amarasinghe, A.M.P.C.; Lankathilake, L.J.M.U.; Wijesekara, E.R.J.M.D.D.P.; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Waste management stands as a critical global environmental challenge, with a growing emphasis on waste avoidance and the generation of revenue through byproduct recovery. Pollution prevention strategies aim to minimize waste generation, while waste minimization efforts focus on reducing waste volume or toxicity, often through water recycling, process modification, and byproduct recovery. In this context, the utilization of distillery effluent in agriculture presents an opportunity to save on fertilizer costs, enhance agricultural output, and mitigate pollution. However, molasses-based distilleries, along with their primary product, alcohol, generate significant volumes of wastewater known as spent wash. Improper disposal of spent wash into water bodies or land leads to a host of environmental issues. Consequently, recent efforts have shifted towards waste minimization and revenue generation through byproduct recovery. This study focuses an approach to address the challenge of distillery spent wash management by drying the spent wash and utilizing the resulting dried solids as an alternative fuel for boilers. The distillery spent wash contains approximately 14.6% solid content, and the dried solids have a gross calorific value of 13840 J/g. Furthermore, the dried solids possess an ash content of 2.26%, with the ash containing a notable 36.7% potassium oxide content. By transforming distillery spent wash into a valuable resource for boiler fuel, this research not only addresses waste management concerns but also offers a sustainable solution for revenue generation. The utilization of dried solids as an alternative fuel for boilers contributes to reducing environmental pollution associated with improper spent wash disposal while offering a viable source of renewable energy. This study underscores the potential of waste-to-energy initiatives in fostering sustainable waste management practices and enhancing economic viability in the distillery sector.
item: Conference-Full-text
Effect of fracture stiffness in a fault damage zone on seismic source parameters of induced fault-slip
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Gang, M; Sainoki, A; Kodama, J; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
It is well recognized that inherent stress concentration within a fault damage zone may lead to induced fault-slip, resulting in severe damage to underground facilities. Previous research suggests that the intensity of fault-slip is influenced not only by the mechanical properties of the fault core but also by the stiffness of the surrounding rock mass, implying that fracture stiffness could be an important factor that needs to be studied. Therefore, in this study, the effect of the fracture stiffness on seismic source parameters of induced fault-slip is investigated using a mine-wide scale heterogeneous continuum model. The model is constructed based on a discrete fracture network within a fault damage zone, utilizing the crack tensor theory and boundary traction method. The fault core is simulated as a discontinuous plane with interface elements at the center of the model, and fault-slip is induced by gradually reducing the effective normal stress on the fault plane. Seismic source parameters are computed and analyzed under various fracture stiffness conditions. Seismically radiated energy is defined as the work done by the stress perturbation across a closed surface at a distance from the earthquake source, while seismic moment is calculated using the moment tensor of a seismic source in an anisotropic medium. This study investigates increasing fracture stiffness while maintaining a normal-to-shear stiffness ratio of three. Dynamic analysis results reveal a notable impact of fracture stiffness on seismically radiated energy and seismic moment, both of which decrease significantly with increasing fracture stiffness. These findings imply the importance of considering fracture stiffness for more accurate estimation of seismically radiated energy and seismic moment.
item: Conference-Abstract
Enhancing Co2 mineralisation in steel slag with amines for developing a waste to construction material
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Takebe, K; Elakneswaran, Y; Yoda, Y; Kitagaki, R; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Global warming has become an urgent issue due to the increasing atmospheric emission of CO2. In Japan, the steel industry emits a large amount of CO₂ and produces steel slag as an alkaline waste product. Using this steel slag to absorb CO₂ in flue gas is an effective approach for CO₂ emissions and recycling. This study introduces a novel technology utilizing amines to facilitate CO₂ sequestration in blast furnace slag. This innovative approach demonstrates significant potential and flexibility compared to conventional CO₂ capture technologies. In this study, changes in the carbonation efficiency of slag with three types of amines (N-Methyldiethanolamine (MDEA), 2-(Methylamino)ethanol (MAE), 2-Amino-2-methyl-1-propanol (AMP)) were investigated. In addition, this study examined the effect of Portland cement on the carbonation efficiency. In wet carbonation, the CO₂ fixation process entails the introduction of 1 mol/L of amine, water, slag, and cement, followed by a 24-hour leaching process and subsequent 24-hour carbonation. The results showed that adding AMP and cement exhibited the most significant increase in carbonation efficiency, resulting in the formation of 11.07% of the solid weight as CaCO₃, as confirmed by thermogravimetric analysis (TGA). Changes in calcium ion concentration and pH were also investigated in this study. The results showed that a small amount of Ca²⁺ dissolution and an increase in pH occurred in the early stages of the reaction and that the majority of Ca²⁺ dissolution occurred simultaneously with carbonation. In dry carbonation, slag cement paste, made by mixing amine, slag, and cement, was carbonated for 28 days after a 28-day curing period to determine changes in its properties. W/S ratio is 10, slag/cement ratio is 19, amine concentration is 1 mol/L, and CO₂ concentration is 0%, 0.04%, 5%, and 15％. Strength tests showed an increase in strength in the slag cement paste with the addition of MDEA.
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Enhancing concrete sustainability through carbonated recycled cement powder: a review
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Mylvaganam, N; Yogarajah, E; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Concrete is a vital construction material, but the rapid urbanization has led to a significant accumulation of demolished concrete, especially in developing countries. Despite efforts, only a small fraction of this concrete is recycled, leading to environmental challenges. However, countries like Japan have successfully recycled a large portion of their demolished concrete, primarily for use in road subbase and as Recycled concrete aggregate (RCA) which is typically yields lower quality compared to natural aggregate (NA). Additionally, during RCA production, a significant amount of cement powder is generated, which has the potential to be used as a supplementary cementitious material (SCM). Recent research has explored various valorisation methods for recycled cement powder (RCP), with carbonation emerging as the most sustainable option. Carbonated RCP not only stores CO2 but also improves concrete properties such as compressive strength and durability. Considering the environmental impact of traditional cement manufacturing, the utilization of SCMs, such as carbonated recycled cement powder (cRCP), has emerged as a promising strategy. This approach promotes sustainable recycling practices and contributes to ecological conservation efforts, aligning with the circular economy philosophy. This review highlights recent findings on the accelerated carbonation treatment of RCP, exploring its benefits and applications as a sustainable building material
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Evaluation of satellite-derived gravity field models in offshore and coastal regions of Sri Lanka
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Wijesooriya, WMARK; Prasanna, HMI; Gunathilaka, MDEK; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
To understand many geophysical phenomena, including ocean circulation, tectonic plate movement, and the Earth’s interior, it is important to study the Earth’s gravity field. During the past three decades, satellites have measured the Earth’s static gravity. As a result, high-resolution global gravity field models have been available. This paper aims to examine the appropriateness of the satellite derived gravity field models for the offshore and coastal regions of Sri Lanka.While these eight gravity field models with ID 155-EIGEN-6S4 V2, 168-Tongji-Grace 02K, 171-GO-CONS-GCF2-TIM-R6, 174-ITSG-GRACE 2018S, 178-Tongji-GMMG2021S, 148-EIGN-6C4, 152-GECO, 167-SGG-UGM-1, and 177-SGG-UGM2 were used for the study. The mean difference value, standard deviation value, and Root Mean Square values modeled by each of the model between the observed gravity data and the BGI observed gravity data. The results indicated that 171-GO-CONS-GCF2-TIM-R6 and 177-SGG-UGM2 is the more suited model for the coastal and offshore region of Sri Lanka. The study used the SARAL-Altika satellite Altimetry data to investigate the relationship between Mean see surface height and observed gravity. No significant relationship between Mean sea surface height and marine gravity is indicated by. In addition, the influence of gravity model type on each of the LEO satellite orbit predictions was also studied. The findings of the research demonstrate that the optimal type of gravity model applied for LEO satellite orbit prediction depends on a short-term or long-term predictions. The models JGM3, EGM2008, and GL04C are more appropriate for short-term predictions, while the models JGM3, EGM96, and EIGEN2 are the best for long-term predictions. The gravity order and permanent tides also have to be taken into account for the orbital prediction.In conclusion, this research provides valuable insights into the suitability of various satellite-derived gravity field models for Sri Lanka's coastal and offshore regions. The findings also emphasize the need to consider the impact of gravity models on LEO satellite orbit prediction, particularly for new applications such as LEO navigation, which require real-time precise orbits.
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Evaluation of use of Tea waste Bio-Char (TBC) as alternative filler for Natural Rubber (NR)
Iresha, H; Egodage, SM; Weerakoon, CS; Muthukumarana, PU; Hewamallikage, YR
Tea waste generated in tea factories, which is the portion that cannot be marketed, is an abundant natural waste in Sri Lanka. Some of the tea manufacturers have converted this bulk waste into its bio-char by using pyrolysis in addition of using for composting and soil conditioning. Considering the high carbon content shown in bio-char, and its nature of biodegradability, renewability, high moisture, smells, toxins and electrosmogs absorption ability, and low thermal conductivity, powdered tea waste bio-char (TBC) can be used as filler in rubbers and will tend to use in a wide spectrum of applications. Bio-char obtained from different natural sources have been researching for different applications especially as filler for different rubbers. However, using TBC in NR as filler is novel. This study adduces the results of proximate analysis of TBC, cure properties, and mechanical properties of TBC/NR composites such as tensile properties, tear strength, hardness, with respect to TBC particle size (125 µm< X < 250 µm and 125 µm X)and loadings from 10 phr to 50 phr at 10 phr intervals. The properties were compared with those of NR composites prepared with carbon black conventional filler (N330). Microscopic images of cross sections of composites were used in order to explain the trends in properties obtained.
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Experimental and numerical analysis of dynamic fracture processes in rock and rock-like materials using NRC vapor pressure agent
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Min, G; Fukuda, D; Di, W.; Liu, H; Kawasaki, S; Cho, S; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
This study investigates the fracture characteristics of rocks and rock-like materials subjected to the Nonex Rock Cracker (NRC), a vapor pressure crushing agent. The NRC generates vapor pressure by instantaneously vaporizing a crystallized water mixture through the thermite reaction. Both experimental methods, using high-speed cameras and dynamic pressure gauges on Polymethyl methacrylate (PMMA) and granite blocks, and numerical simulations with a 3-D combined finite-discrete element method (FDEM) were utilized. Results indicate that gas pressure infiltrating pre-existing cracks primarily drives crack propagation. The study concludes that accurately modeling gas injection into initiated cracks during deflagration is essential for reasonable numerical simulations of rock fracturing processes using NRC.
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Exploration and characterization of potential iron ore occurrence in Pelpitigoda, Sri Lanka
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Wijethunge, HP; Appuhamy, RPMC; Vilojan, M; Ratnayake, NP; Abeysinghe, AMKB; Premasiri, HMR; Rohitha, LPS; Dushyantha, NP; Batapola, NM; Dilshara, RMP; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Iron is widely used across industries in worldwide, with an annual usage of over 1.8 billion tonnes, steadily increasing over decades. Due to this high consumption of iron, it is crucial to find new sources of iron. Therefore, this research project was designed with the objectives of exploring the potential iron occurrence and characterize the mineralogy and geochemistry of the Pelpitigoda area. The methodology comprises two phases. In the initial phase, geological settings were studied to understand the rock formations and structures surrounding the area. It was followed by a magnetic susceptibility survey to identify variations and anomalies, along with systematic sample collection across the deposit. The phase two was completed with laboratory analysis, including sample preparation, colorimetry, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Notably, colorimetry results from phase two indicated iron content ranging between 40-60 wt% in the samples, with XRD analysis identifying goethite as the predominant mineral, alongside magnetite, hematite, and gibbsite. XRF results revealed an average iron content of 38.47 wt%. Furthermore, ICP-MS analysis showed lower potential for valuable metals like V, Cr, Co, Ni, and Zn in the area. The significance of this research lies in its potential to identify a new iron ore occurrence in the Pelpitigoda area. The comprehensive characterization of the mineralogy and geochemistry provides valuable insights into the composition and distribution of iron-bearing minerals in the area. Future work entails completing the last phase of roasting the samples to extract iron oxide, followed by comprehensive laboratory testing of the prepared samples.
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Extraction potential of nickel from native hyperaccumulator plants from Ginigalpelessa serpentinite deposit
(Department of Architecture University of Moratuwa, 2024) Dilshara, RMP; Abeysinghe, AMKB; Premasiri, HMR; Ratnayake, NP; Senarath, WTPSK; Ratnayake, AS; Dushyantha, NP; Batapola, NM; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Serpentine soils are low-grade Ni resources that have been utilized widely to extract Ni to meet its burgeoning demand in the renewable energy sector. However, the economic impracticability of Ni recovery by conventional mining techniques has been directed towards Ni phytomining, in which native hyperaccumulators grown in serpentine soils are used for commercial Ni recovery. In this context, the Ginigalpelessa serpentinite deposit in Sri Lanka harbors a wide variety of plants that can accumulate high Ni concentrations from the soil. Despite the promising Ni potential (0.4-1.7%) in the Ginigalpelessa serpentinite deposit, the lack of detailed studies on the hyperaccumulation ability of native plant species and proper extraction methods retards the commercial application of Ni phytomining in this deposit. Therefore, the present study carried out ex-situ phytomining trials using two native hyperaccumulator species namely, Crotalaria verrucosa and Apluda mutica. The harvested biomasses were then incinerated to produce Ni-rich bio-ores, which were analyzed for Ni concentration using Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The bio-ore of C. verrucosa contained 7,279 ± 106 mg/kg of Ni whereas the bio-ore of A. mutica showed 3,867 ± 39 mg/kg of Ni. The bio-ore of A. mutica was used for the leaching experiments due to its highest abundance in the deposit. The leaching assays were carried out with A. mutica bio-ore under different pulp densities (100 g/L and 200 g/L) and H2SO4 concentrations (1 mol/L and 5 mol/L). The bio-ores used in leaching experiments were produced from an open flame and muffle furnace (at 550 ⁰C). The highest leaching efficiency was observed as 59% in open burnt samples (leachate Ni concentration = 649 mg/kg and total Ni concentration = 1,098 mg/kg) under 100 g/L pulp density and 5 mol/L H2SO4 concentration. The overall low leaching efficiency of bio-ore can be attributed to the formation of an aluminum silicate matrix (Al2O3.2SiO2) during leaching experiments which inhibits the Ni leaching. Therefore, the present study requires further investigations to optimize the leaching efficiency to implement a sustainable Ni extraction method for the local serpentinite bodies. Financial assistance from the Senate Research Committee, University of Moratuwa (Grant no: SRC/LT/2021/15) is acknowledged.
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Fundamental study of the influences of discontinuities on rock slope displacement due to excavation
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Kubo, T; Zhang, C; Sainoki, A; Kodama, J; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
In the Higashikagoe limestone quarry, discontinuities are thought to be one of the factors contributing to the deformation of the rock slope. In this study, we investigated the impact of discontinuities and dip angles on slope deformation through numerical simulations, developing four models: a model without any discontinuity and three models with discontinuities of different dip angles. Results showed that discontinuities significantly influence deformation, with forward movement observed in models with discontinuities, aligning with field measurements. This suggests that discontinuities are critical to the deformation of the rock slope in the Higashishikagoe quarry.
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Identification of the optimum replacement ratio of quarry dust as a substitute for sand and cement in cement plastering
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Dhananjaya, MMP; Gajanan, P; Bandara, RGTI; Illankoon, IMTN; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
River sand and cement are important construction materials, but their scarcity creates significant challenges for the construction industry. Quarry dust is being explored as a possible alternative, as crushed rock is a common aggregate source in Sri Lanka. Therefore, this study focuses on determining the possibility of using quarry dust as a partial replacement for cement and river sand in plastering mortar. Selected Manampitiya river sand and quarry dust from four quarries were subjected to sieve analysis (ASTM C136). Four quarry dust samples obtained from two different crusher types (cone crusher and vertical shaft impact crusher) were sieved to separate 0.1-2.36 mm particles and <0.1 mm particles to replace with sand and cement, respectively. Plastering mortar’s cement-sand ratio was selected as 1:5 and developed in 12 mix proportions, varying the replacement of sand with quarry dust (0.1-2.36 mm particles) at 0%, 33%, 50% and 100%, as well as the replacement of cement with quarry dust (<0.1 mm particles) at 0%, 5% and 10%. The flow table test (ASTM C1437) was performed for each mix proportion to obtain the water-cement ratio of plastering mortar, which gives acceptable workability (105-115 mm). Four 50 mm cubic specimens from each mix proportion were prepared according to the obtained water-cement ratio. The cubic compression test (ASTM C109M) and water absorption test (ASTM C140) were performed for the cubic specimens after the completion of the 28-day curing period. Results indicate that the sand and quarry dust samples analysed are poorly graded. An increase in quarry dust in the plastering mortar reduced the workability, but it reached an acceptable range with a water-cement ratio of 1.1-1.2. All tested specimens indicate compressive strength >3 MPa, which was the minimum strength required for plastering. The compressive strength results indicate that the cement replacement can be further increased with 100% sand replacement. The durability of plaster slightly reduces with an increase in quarry dust proportion, indicating a maximum of 2.4% increment in water absorption for a 100% sand-replaced, 10% cement-replaced specimen compared to a specimen made from 100% sand. Furthermore, 100% sand replacement can achieve a cost reduction of 27%. Hence, it is recommended to replace sand 100% with quarry dust 0.1-2.36 mm particles for cement plastering.
item: Conference-Abstract
The Impact of gas impurities on CO2 storage in depleted oil field with carbonate reservoirs
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2014) Muer, A; Elakneswaran, Y; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
The carbon dioxide capture and storage (CCS) is considered as a promising technology for carbon dioxide emission reduction. High-purity CO2 mixture gas is separated from the flue gas and pumped into underground for a long-term storage. The impurities of gas can affect the trapping mechanisms. Various research studies about how impurity changes permeability were carried out. However, the effect of impurities in long-term trapping mechanisms is still unclear. This research studies the effects of H2S, SO2, and NO2 in CCS for a long-term period of 2000 years using a PHREEQC geochemical simulator. The simulation presents formation water and rock samples from the previous research and the mixture gas groups to emphasis the effect of each impurity. The simulation contains two parts: the equilibrium block and the kinetics block. The former is to simulate the reversible reaction between the pure phases and the aqueous phase, which is defined by the equilibrium constant and dependent on the temperature. The latter is to simulate how phases react by time defined by kinetics rate, which is defined by the Arrhenius equation and depends on the pH, temperature, surface area and other reaction condition constants. Firstly, the gas and formation water are input into the equilibrium block to get CO2 enriched solution and remaining gas components. Then, the remaining gas and solution and mineralogy are put into the kinetics block. Results indicate a shift from mineral trapping to solubility trapping in the presence of impurities, with a significant decrease in pH affecting CO2 storage ratios. Furthermore, the changes in each mineralogy and the effects of each impurity are discussed
item: Conference-Full-text
Incident of ground collapse up to daylight and recovery actions taken in shallow Ranwediyawa tunnel in Sri Lanka
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Perumal, M; Wanigasekara, WADID; Isuranga, SNAMTK; Narangoda, SRAIB; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
The Ranwediyawa tunnel was constructed under the Mahaweli Water Security Program (MWSIP) to minimize the social impacts on the villages, where the irrigation canal runs through the village. The tunnel was slightly redirected from the original canal path which was planned to run through the village road having a deep excavation over a length of 620m with a mixed ground condition. The area has a high ground water table and seasonally varies slightly due to the area's weather pattern with varying topography and which has a deep open excavation from 12m to 18m for the construction of cut & cover conduit. Having a shorter period of design the Ranwediyawa tunnel was designed with a ground cover varying from 9m to 20m, including 5 support classes according to the RMR classification. Both tunnel portals start with completely to slightly weathered rock and move into moderately weathered to fresh rock. Both tunnel drives were driven by mechanical excavation with NATM concept with few small chimney collapses, however, a major collapse occurred once the upstream drive reached the rock-type boundary and it was developed to daylight. This paper describes the details of the initial excavation procedures, the major geological conditions and the recovery procedures which were taken to complete the tunnel excavation. Also, this paper covers special arrangements made by the Contractor in the shortage of resources available in the project as the incident occurred during the spreading of the COVID-19 period. The tunnel drive successfully passed this weak geological area with long pipe roofing support before the tunnel excavation after two months with a few days of site closure due to the identified worker getting COVID-19 in the tunnel team.
item: Conference-Abstract
International Symposium on Earth Resources Management & Environment 2024 (Pre-Text)
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
item: Conference-Full-text
An Investigation into the pretreatment methods for the extraction of platinum (Pt) from platinum oxide ores
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Tatenda, MM; Park, I; Ito, M; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Platinum (Pt) is known to be one of the rarest metals in the world.lt’s unique physical and catalytic properties make it largely valued across a number of various demand segments and technologies. The four main segments of Pt demand are automotive (30-40%), industrial (27-36)%, jewelry (23-30%), and investment ~10%. There has been a global Pt demand with automotive demand being on the highest rising to 16% in 2023 and predicted to grow in 2024. To meet the current rising demands, there has to be an increase in the production of platinum however, there has been a fast depletion of platinum group metals (PGMs) bearing sulfide ores which has activated interest in exploring the likelihood of the recovery of PGMs from near-surface oxidized PGM ores. In Zimbabwe and South Africa, there is an estimated resource of over 500MT of PGM oxides that is either unmined, mined, stockpiled, or discarded as overburdened waste. The recovery of these PGMs has shown to be difficult to process by conventional means as an alternative source to sustain the production of PGMs. Several attempts to process the oxidized ores via conventional hydrometallurgical methods by concentrator plants in Zimbabwe and South Africa have been made. The attempts saw some PGM values that fall within the floatable size range not being floated and successively reporting to the tailings. Attempts to process oxidized PGM ore have been made worldwide using different methods. This paper scrutinizes the different hydrometallurgical methods previously used to process the oxidized PGM ores and their recoveries, the challenges encountered and the research gaps to be considered for future research. Recommendations for future research will also be given based on current research techniques in the mineral processing field.