Browsing by Author "Kawasaki, S"

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item: Conference-Full-text
Beachrock identification using geology and geophysical approaches in Indonesia
(Department of Earth Resources Engineering, 2019-08) Daryono, LR; Nakashima, K; Kawasaki, S; Titisari, AD; Barianto, DH; Suyanto, I; Rahmadi, A; Dissanayake, DMDOK; Samaradivakara, GVI
A unique carbonate rock developed naturally as a natural barrier presumably appropriate for advanced marine ecosystems including microbiotas in shorelines. A great deal of progress has been made in recent years to investigate the chemical characteristics of beachrocks. Beachrocks found in Krakal-Sadranan Beach can be categorized into non-beachrocks, unconsolidated beachrocks (similar to carbonate sands), and well-consolidated beachrocks, which mainly consist of rocks and minerals. A depletion of Sr concentration in the beachrocks indicates that the diagenetic processes have progressed from the land to the seashore, most likely post-deposition of the beachrock and carbonate sand. An increased concentration of Rare-Earth-Element (£REE), both heavy REE (Tb, Dy, Y, Ho, Er, Tm, Yb and Lu) and light REE (La, Ce, Pr, Nd, Sm, Eu and Gd) signals that the beachrock deposition process happened at oxidative environmental conditions. Unmanned aerial vehicle (UAV) drone mapping, geological analysis, and geophysical surveys were conducted to detect the underground structure of the beachrocks and to emphasize the coastal mapping based on targeted beachrock.The mechanism of beachrock formations obtained in this study would be a novel concept and applicable for the coastal zone improvements and preservations for further studies. on targeted beachrock. The mechanism of beachrock
item: Conference Full-text
Bioremediation of lead-contaminated mine waste using microbially Induced carbonate precipitation
Mwandira, W; Nakashima, K; Kawasaki, S; Abeysinghe, AMKB; Dassanayake, ABN; Elakneswaran, Y
The aim of this study was to use microbially induced calcium carbonate precipitation (MICP) technique to bioremediate lead using bacterium Pararhodobacter sp. Laboratory scale experiments conducted, achieved complete removal of lead. This result was further confirmed by SEM and XRD analysis that indicated coprecipitation of calcium carbonate (CaCO3) and cerussite (PbCO3). Furthermore, syringe test demonstrated that MICP based sequestration of heavy metals via coprecipitation with calcium carbonate may be useful for lead bioremediation. Very few low-cost in situ heavy metal treatment processes for lead bioremediation are available; therefore, bioimmobilization of lead by MICP has the potential for application as a low-cost and eco-friendly method for heavy metal remediation.
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 Full-text
Effect of organic bio-polymer on bio-mineralization of CaCO3
Nawarathna, THK; Nakashima, K; Kawasaki, S; Abeysinghe, AMKB; Dassanayake, ABN; Elakneswaran, Y
Organic matrix in the biogenic CaCO3 has a significant influence on the CaCO3 crystal growth, its polymorphs and morphology. In this research, effect of the cationic and anionic organic bio-polymers on the crystallization of CaCO3 was investigated in microbial induced carbonate precipitation (MICP) process. In the current study, poly-L-lysine and poly-glutamate were used as cationic and anionic biopolymers, respectively. Urea hydrolysis by ureolytic bacteria Pararhodobacter sp. led to CaCO3 formation in the presence of Ca2+ ions. The reaction was conducted with the addition of the polymers under different conditions. After oven-drying precipitation, the amount of precipitate was measured and morphology of the precipitate was analyzed by using scanning electron microscope. Bell-shaped curve was obtained in the relationship between the amount of the precipitate and the poly-L-lysine concentration. However, amount of precipitate remained approximately constant with the increase of the poly-glutamate concentration. In the presence of poly-L-lysine, morphology of the crystals changed from well-developed rhombohedral crystals to ellipsoidal shaped aggregates. But in poly-glutamate addition, polyhedral and spherical crystals are predominant.
item: Conference-Full-text
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.
item: Conference-Full-text
Experimental optimization of biocement formation: alternative countermeasure for surface erosion of cut slope
(Department of Earth Resources Engineering, 2018-08) Gowthamani, S; Nakashima, K; Ebina, K; Kawasaki, S; Abeysinghe, AMKB; Samaradivakara, GVI
The research w o r k aims to assess the feasibility of i n t r o d u c i n g the microbial induced carbonate p r e c i p i t a t i on (MICP) as an alternative technique for surface stabilization of the cut slopes by augmenting potential indigenous ureolytic bacteria. A set of column solidification tests was conducted on embankment soil (Hokkaido expressway, Japan) to optimize the performance of bacteria regarding bacterial population of culture solution (optical density (OD600) from 1 to 6), and concentration of Ca^* and urea i n cementation solution (0.5 m o l / L and 1 mol/L) at the temperature of 20°C. The UCS of treated samples was estimated using needle penetrometer, and the microstructure of the treated specimens was observed using scanning electron microscope (SEM). The results reveal that the UCS of the specimen increases w i t h increasing ODeoo w i t h o u t any clogging w i t h i n the samples. Treating the soil using 1 m o l / L concentrated (Ca2+ and urea) cementation solution and bacterial culture w i t h ODeoo of 6 results the highest UCS of 7.5 MPa while achieving relatively a homogeneous solidification along the column profile. The micrographs of the treated specimen confirms that the rombohedral calcium carbonate crystals formed w i t h i n the pores of soil matrix, w h i c h has effectively bonded the adjacent soil particles, and contributed to enhance the strength significantly at the o p t i m i z e d treatment condition.
item: Conference-Full-text
A preliminary investigation on isolation and identification of marine bacteria for biocementation in nearshore environments
(Department of Earth Resources Engineering, 2018-08) Nayanthara, PGN; Dassanayake, ABN; Nakashima, K; Kawasaki, S; Abeysinghe, AMKB; Samaradivakara, GVI
Microbial Induced Carbonate Precipitation (MICP) is a widely explored technique that involves utilizing bacterially produced carbonate biominerals for improving the engineering properties of soils. When this novel approach is used in cementing sandy soils in nearshore areas, it is necessary to identify suitable bacterial strains which are resistant to high saline dynamic marine environments. Thus, current study was carried out to isolate and identify ureolytic bacteria from Sri Lankan beach sand and to check their suitability for use in MICP. To accomplish this, bacterial strains were isolated from beach sand samples and urease activity was determined. MICP capability was evaluated by cultivating the species on agar plates containing CaCh and urea. Based on these results, four isolates having high feasibility to induce bacterially precipitated calcium carbonates were selected and identified by 16S rDNA gene sequencing. Two strains were identified as belonging to Halomonas sp. and other two to Sulfitobacter sp. and OceanobaciUus sp. genera. Further analysis was done to determine the bacterial cell growth of isolates at different temperatures and concluded that all four isolates have a more stable growth at temperature close to 30°C. Isolates were evaluated for their biosafety and found to be non pathogenic. However, detailed analysis on biomineralization by the selected isolates and their biological behaviour is recommended prior to any large scale applications.
item: Conference-Abstract
Silica and polyphenol-based adsorbents of heavy metals fabricated by enzymes
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Maulidin, I; Nakashima, K; Naota, R; Takano, C; Kawasaki, S; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
Lead (Pb) contamination in water sources poses severe health risks to both humans and ecosystems. Conventional methods for Pb removal often rely on chemical treatments or expensive filtration systems, which can be economically burdensome and environmentally hazardous. In response to this pressing issue, this study presents a novel approach leveraging biologically inspired fabrication techniques by using enzymes for the development of an efficient and ecofriendly silica-based biosorbent incorporating poly-tannic acid for efficient Pb (II) ion removal from aqueous solutions. The process involves the biological immobilization of laccase enzyme on the bead’s surface via a protective silica layer formed by the functional silica-polymerizing enzyme, silicatein. Silica beads were chosen as the support material for enzyme immobilization due to their favourable chemical and physical properties and natural compatibility with the silicatein enzyme. This innovative method prevents the immobilized enzyme from leaching and enhances laccase immobilization on the beads, ensuring the enzyme thermostability, and maintains its activity even under harsh conditions such as at an acidic-alkaline pH. Furthermore, poly-tannic acid was formed on the bead surface through oxidative polymerization mediated by immobilized laccase. Successful coverage of poly-tannic acid polymerized by laccase on the beads was confirmed by using SEM-EDS and FTIR spectra. The silicatein-treated biosorbent exhibited high laccase loading capacity and retained about 48% of its initial activity when tested under alkaline conditions. Additionally, it showed a remarkable enhancement compared to the biosorbent treated without silicatein in activity across varying temperatures which indicated favourable thermostability properties. The silicatein-treated biosorbent revealed its effectiveness in removing Pb(II) ions from aqueous solutions with a maximum adsorption capacity of 52.4 mg/g, a threefold increase compared to that of the biosorbent without silicatein. This silica-based biohybrid material presents advantages over conventional methods, including higher adsorption capacity and enhanced stability, offering a promising environmentally friendly solution for heavy metal bioremediation in water sources.