• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.103-108
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• 2008

Riverbed change is greatly influenced by artificial factors such as dam construction, gravel collection, and river improvement. This study simulated a long-term bed change based on the GSTARS3 model using actual data from the area downstream of the Geum River Daecheong Dam and compared the estimation with a section of the actual measurement. As a result, it was found that the section of the actual measurement was far lower than the result of the simulation in terms of long-term bed change. While the area downstream of Daecheong Dam displayed approximately an average of 2.29 m of streambed degradation on average while the upper stream area showed approximately 0.63 m of bed degradation over 24 years. In the simulation of the area downstream of Daecheong Dam based on the GSTARS3 model, similar bed degradation was observed. However, a great difference was detected between the result and the actual measurement. According to the cause analysis, the riverbed in the area downstream of Daecheong Dam has continuously degraded due to the dam construction and mass collection of gravel. The mass collection of gravel was the main cause of riverbed change. It was found that about 76% of all riverbed degradation was caused by the mass collection of gravel.

• SUVANNABHUMI
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• v.16 no.2
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• pp.215-261
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• 2024

In the 1960s, the Aoheng, a small tribal group with immense territories on the upper Mahakam River, began out-migrating to downstream settlements in search of better living conditions. A trickle of young men, then their families, and more sizable groups, they settled in various towns along the river. In Samarinda, the provincial capital, they came to form a community of several hundred. When the powerful forest product boom (c. 1990) for the P. R. China market opened up the hinterland to extractive ventures, many Aoheng returned home to protect their rich natural resources from forceful outsiders. After 1998, decentralization policies established scores of new provinces, regencies, and districts across the country. Soon, West-Kutai was created as the interior "Dayak" regency, upstream and autonomous from the Moslem-Malay coastal regions. Coal mining and oilpalm plantations massively intensified, while Sendawar, its capital, offered hundreds of civil-service jobs and business opportunities. In 2012, West-Kutai was split to create yet another regency, Upper-Mahakam, prompting robust Aoheng reflux/return moves toward its upstream capital, Ujoh-Bilang. Already open to wild-frontier-style inroads by outsiders, it will soon be flooded by industrial ventures. The Aoheng, bound to become a minority in their own district, are struggling to defer their inevitable final dissolution.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_2
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• pp.521-527
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• 2013

Rule set is an important step which impacts significantly on accuracy of object-oriented classification result. Therefore, this paper proposes a rule set to extract land cover from Landsat Thematic Mapper (TM) imagery acquired in Donganh, Hanoi, Vietnam. The rules were generated to distinguish five classes, namely river, pond, residential areas, vegetation and paddy. These classes were classified not only based on spectral characteristics of features, but also indices of water, soil, vegetation, and urban. The study selected five indices, including largest difference index max.diff; length/width; hue, saturation and intensity (HSI); normalized difference vegetation index (NDVI) and ratio vegetation index (RVI) based on membership functions of objects. Overall accuracy of classification result is 0.84% as the rule set is used in classification process.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.441-441
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• 2002

In order to ensure a balance between economic development and a healthy Mekong Basin environment supporting natural resources diversity and productivity critical to the livelihood of its 65 million inhabitants, the Mekong River Commission (MRC) has been investigating the use of radar to remotely characterize and monitor the diversity, complexity, size and connectivity of the Basin's aquatic habitats. The PACRIM AIRSAR Mission provided an opportunity to evaluate the usefulness of radar technology to derive information for assessing, forecasting and mitigating possible cumulative and long-term impacts of development on the natural environment and the people's livelihood. This paper presents the results of mapping wetland cover types using multi-polarimetric radar for an area of the north-western corner of the Tonle Sap basin with data acquired from the AIRSAR Mission in September 2000. The implementation of a newly developed segmentation classification routine used to derive the image classification is described and the results of a fieldwork campaign to check the classification is presented.

• Advances in concrete construction
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• v.4 no.3
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• pp.221-230
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• 2016

This paper presents a preliminary study on the influence of laterite soil replacing conventional fine aggregates on the strength properties of GGBS-blended-concrete. For this purpose, GGBS-blended-concrete samples with 40% GGBS, 60% Portland cement (PC), and locally available laterite soil was used. Laterite soils at 0, 25, 50 and 75% by weight were used in trails to replace the conventional fine aggregates. A control mix using only PC, river sand, course aggregates and water served as bench mark in comparing the performance of the composite concrete mix. Test blocks including 60 cubes for compression test; 20 cylinders for split tensile test; and 20 beams for flexural strength test were prepared in the laboratory. Results showed decreasing trends in strength parameters with increasing laterite content in GGBS-blended-concrete. 25% and 50% laterite replacement showed convincing strength (with small decrease) after 28 day curing, which is about 87-90% and 72-85% respectively in comparison to that achieved by the control mix.

• Earthquakes and Structures
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• v.22 no.4
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• pp.431-437
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• 2022

One of the best choice for transportation of oil and gas at the end of rivers or seas is concrete pipelines. In this article, a concrete pipe at the end of river is assumed under the earthquake load. The Classic shell theory is applied for the modelling and the corresponding motion equations are derived by energy method. An external force induced by fluid around the pipe is asssumed in the final motion equations. For the solution of motion equations, the differential quadrature method (DQM) and Newmark method are applied for deriving the dynamic deflection of the pipe. The effects of various parameters including boundary conditions, fluid and length to thickness ratio are presented on the seismic response of the concrete pipe. The outcomes show that the clamped pipe has lower dynamic deflection with respect to simply pipe. In addition, with the effect of fluid, the dynamic defelction is increased significantly.

• Earthquakes and Structures
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• v.22 no.5
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• pp.439-445
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• 2022

One of the best choice for transportation of oil and gas at the end of rivers or seas is concrete pipelines. In this article, a concrete pipe at the end of river is assumed under the earthquake load. The Classic shell theory is applied for the modelling and the corresponding motion equations are derived by energy method. An external force induced by fluid around the pipe is asssumed in the final motion equations. For the solution of motion equations, the differential quadrature method (DQM) and Newmark method are applied for deriving the dynamic deflection of the pipe. The effects of various parameters including boundary conditions, fluid and length to thickness ratio are presented on the seismic response of the concrete pipe. The outcomes show that the clamped pipe has lower dynamic deflection with respect to simply pipe. In addition, with the effect of fluid, the dynamic defelction is increased significantly.

• Journal of Korea Water Resources Association
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• v.43 no.7
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• pp.657-666
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• 2010

The adjustment processes of mining pits in the disturbed channels by sand or gravel mining were investigated by laboratory experiments in this study. The pit migrated with speed when the river bed was steep. The pit migrated slow and steady when the pit was filling with sand, but the pit migrated with speed after the filling processes was finished. The submerged angle of repose in the pit was nearly constant during the pit was filling. The pit was filled with sand with speed as the channel slope was increased. It took time for the pit to be filled with sand as the pit dimension was increased. This meant that the disturbed channels by sand or gravel mining to adjust the new environment was dependent on the slope of the channels and the dimension of the pits. The dimensionless pit length was short and the dimensionless pit depth was shallow as the time was increased. The dimensionless pit depth was shallow, but the dimensionless pit migration speed was increased as the dimensionless shear velocity and the migration speed of the pit were increased. The dimensionless pit depth was increased with the dimensionless bar migration speed. The shape of the pit was deformed and migrated downstream in accordance with the location and shape of the biased bar front which was developed upstream.

• Geomechanics and Engineering
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• v.24 no.4
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• pp.349-358
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• 2021

The Brazilian test has been widely used to determine the indirect tensile strength of rock, concrete and other brittle materials. The basic assumption for the calculation formula of Brazilian tensile strength is that the elastic moduli of rock are the same both in tension and compression. However, the fact is that the elastic moduli in tension and compression of most rocks are different. Thus, the formula of Brazilian tensile strength under the assumption of isotropy is unreasonable. In the present study, we conducted Brazilian tests on flat disk-shaped rock specimens and attached strain gauges at the center of the disc to measure the strains of rock. A tension-compression bi-modular model is proposed to interpret the data of the Brazilian test. The relations between the principal strains, principal stresses and the ratio of the compressive modulus to tensile modulus at the disc center are established. Thus, the tensile and compressive moduli as well as the correct tensile strength can be estimated simultaneously by the new formulas. It is found that the tensile and compressive moduli obtained using these formulas were in well agreement with the values obtained from the direct tension and compression tests. The formulas deduced from the Brazilian test based on the assumption of isotropy overestimated the tensile strength and tensile modulus and underestimated the compressive modulus. This work provides a new methodology to estimate tensile strength and moduli of rock simultaneously considering tension-compression bi-modularity.

• Journal of Soil and Groundwater Environment
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• v.23 no.5
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• pp.17-25
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• 2018

The Boroo area in Mongolia is known to have been contaminated with heavy metals due to irregular gold mining activities and the release of mercury from gold extraction process. Soil and mine tailings were collected to analyze contamination patterns of heavy metals in the Boroo area. Analyses revealed that mercury, arsenic and cadmium concentrations exceeded the regulatory standard of the nation (Mongolia National Standard). In case of mercury, about 80% of the survey area was over the limit and the concentration distribution heavily influenced by influx of mercury through water transport. Soil contamination by arsenic was most severe that the concentration exceeded the regulatory limit in almost entire survey area, showing peak concentrations at nearby streams and river along with ore processing facilities. For cadmium, about 20% of the survey area was over the limit with the concentration distribution similar to that of arsenic.