• Economic and Environmental Geology
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• v.39 no.2 s.177
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• pp.191-212
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• 2006

Placer gold deposits is mainly distributed in the Takaoi area. The alluvium is unconsolidated or semiconsolidated deposit consisting of gravel, sand, and soil beds in ascending order. They unconformably overlies the Carboniferous-Permian schist and Cretaceous granodiorite substratum. Based on detailed facies analysis, the alluvium can be interpreted as a typical fluvial deposits containing gravel and sand beds of channel-fill unit and soil deposit of floodplain. Gold grains are included mainly in the gravel bed and vein quartz is only contained gold among all kinds of gravels. These features indicates that the source rock of the gold grain is vein quartz and gold grains are separated from vein quartz during transport and abrasion. The reserves of gold in this area reach to at least 792 kg.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.459-472
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• 2001

The objective of this study is to evaluate the filtration efficiency of deep-bed filters by comparing to single and dual media filters. Pilot-plant tests using four-filter columns were conducted for the comparison of head loss development and filtered water quality. The dual-media filter showed greater initial head loss, but less rate of head-loss development than those of the coarse-sand-0deep-bed filters. For 180 m/day of filtration rate, the dual-media filter produces larger unit production rate by 30-40%, and the turbidities of filtered water were below 0.1 NTU. The initial breakthrough could be effectively controlled by the dual-media filter rather than coarse-sand-deep-bed filters.

• The Korean Journal of Quaternary Research
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• v.23 no.1
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• pp.1-24
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• 2009

Paleosol layers lying on top of the terrace in Jeongdongjin area appear to have been deposited under generally well-drained condition with periodic waterlogging. From a 4.5m-long profile observed, a total of 6 stratigraphic units were identified. Grain-size analysis indicates the dominance of silty and clay materials with some portions with high sand content. Major mineralogical elements are quartz, feldspar, mica and chlorite. Geo-chemical composition shows little change throughout the stratigraphy with some fluctuation in chemical weathering index. Marked increase in magnetic susceptibility is recognizable where stratigraphic unit changes. Soil- wedge layer is developed around 50cm below the surface with concentration of grains of AT tephra (c. 25,000 BP). An OSL date of c. 110,000 BP was obtained from a sand layer lying below the paleosol.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.7
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• pp.83-89
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• 2019

In the conventional casting and forging method, there is a disadvantage that a mold is an essential addition, and a production cost is increased when a small quantity is produced. In order to overcome this disadvantage, a metal 3D printing production method capable of directly forming a shape without a mold frame is mainly used. In particular, overseas research has been conducted on various materials, one of which is a metal printer. Similarly, domestic companies are also concentrating on the metal printer market. However, In this case of the conventional metal 3D printing method, it is difficult to meet the needs of the industry because of the high cost of materials, equipment and maintenance for product strength and production. To compensate for these weaknesses, printers have been developed that can be manufactured using sand mold, but they are not accessible to the printer company and are expensive to machine. Therefore, it is necessary to supply three-dimensional casting printers capable of metal molding by producing molds instead of conventional metal 3D printing methods. In this study, we intend to reduce the unit price by replacing the printing method used in the sand casting printer with the FDM method. In addition, Ag paste is used to design the output conditions and enable ceramic printing.

• Journal of The Geomorphological Association of Korea
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• v.25 no.2
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• pp.15-29
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• 2018

The sediment transport process in a river reflects the process of geomorphological change in the watershed, influencesthe river bed variation and the river channel migration, and is a parametric phenomenon that exhibits a dynamic self-adjusting process. Sediment load is divided into bedload and suspended load depending on the dominant mechanism. Quantitative sediment load is important information for solving river problems. Because it is difficult and time consuming to measure bedload, compared to that ofsuspended load, data on the sediment transport load and the research required for the gravel-bed rivers are insufficient. This study is to analyze the ratio of the bedload to the total sediment load in gravel-bed rivers. The sediment load ratio in gravel-bed rivers increases with the flow rate per unit width, and the rate of the bedload varies more rapidly than the suspended load. The sediment transport efficiency coefficient has been affected by the ratio of the flow depth to the mean diameter of particles and has been dependent on the shear velocity Reynolds number. So $A^{\ast}$ and $B^{\ast}$ are introduced to compensate for the uncertainties such as bed materials, sediment transport, and flow velocity distribution, and the coefficient of bedload ratio has been presented. For the sediment load data in experimental channels and rivers, A* was 3.1. The dominant variables of $B^{\ast}$ were $u_*d_m/{\nu}$ in the gravel-bed and h/dm in the sand-bed. When $B^{\ast}$ the is the same, in the experimental channels the coefficient of bedload ratio was affected by the bed forms, but in the rivers it was of little difference between the gravel-bed and sand-bed.

• Economic and Environmental Geology
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• v.54 no.3
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• pp.365-372
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• 2021

Pebble-bearing clastic carbonate rock which has been found in and around the Jeongseon and Okgye through the field survey was studied in petrological and mineralogical characteristics. We define the clastic carbonate rocks as 'Dolomite-pebble bearing fine sand-sized dolostone, or grainstone', which are characterized by the existence of dolomite single grains and Mg-phengite, and by the subsequent formation of secondary calcite cements. These attributes correspond well with those of the typical Haengmae Formation from Haengmae-dong, Mitan-myeon, Jeongseon-gun, thus the carbonate rocks in the Jeongseon and Okgye areas must belong to the Haengmae Formation. The result suggests that the Haengmae Formation is an independent unit among the Paleozoic lithostratigraphic units in Taebaek basin and lies in the upper part of Jeongseon and Sukbyungsan Formations under the Hongjeom Formation of Pyeongan Supergroup.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.61-69
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• 2023

As global trade and maritime port environments change, the need to respond to larger and faster ships is increasing. Accordingly, new ports are being built around metropolitan cities such as Busan and Ulsan. In general, a compaction method using sand or gravel is applied to the construction of a new port. However, due to the lack of sand or gravel and the difficulty in securing economic feasibility due to the increase in unit price, the deep mixing method has recently been used. Therefore, in this study, CMD-SOIL using circulating resources was applied to the Ulsan area, and the applicability was determined by analyzing the laboratory mixing test and boring results at in-situ. As a result of the test, it was analyzed that it showed more than the design mixing strength, and it was possible to secure the similar performance as blast furnace slag cement. In addition, it was analyzed that the design standard strength can be sufficiently secured as a result of in-situ boring. Therefore, considering the field applicability in the Ulsan, it is judged that the use of CMD-SOIL is possible.

• Journal of the Korean Geotechnical Society
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• v.26 no.9
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• pp.59-69
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• 2010

This study is experimentally investigated for characteristics of lightweight air-trapped soils with uniform quality. Previously, EPS (Expanded PolyStyrene) blocks are often used as lightweight embankment, but many problems such as the level difference and cracks were caused by plastic (creep) deformation. So, a new material development is urgent. By means of alternatives, lightweight air-mixed soil using in-situ soils has been developed and applied to fields. In comparison with EPS block, lightweight air-mixed soil has less plastic (creep) deformation in long period, but the strength characteristics are different according to the soils where they are obtained. Therefore, the quality management of lightweight air-mixed soil is very difficult. Therefore in this study, characteristics of lightweight air-trapped soil using a manufactured sand with uniform quality are investigated. To found out the compression and tensile characteristics of lightweight air-tapped soils, unconfined compression test and splitting tensile test are conducted on the specimens prepared with different unit weight, cement-sand ratio and air-pore.

• Journal of the Korean GEO-environmental Society
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• v.20 no.2
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• pp.41-48
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• 2019

Soil compaction is one of the most important activities in the area of civil works, including road construction, airport construction, port construction and backfilling construction of structures. Soil compaction, particularly in road construction, can be categorized into subgrade compaction and roadbed compaction, and is significant work that when done poorly can serve as a factor causing poor construction due to a lack of compaction. Currently, there are many different types of compaction tests, and the plate bearing test and the unit weight of soil test based on the sand cone method are commonly used to measure the degree of compaction, but many other methods are under development as it is difficult to secure economic efficiency. For the purpose of this research, a portable penetration meter called the Free-Fall Penetration Test (FFPT) was developed and manufactured. In this study, a homogeneous sample was obtained from the construction site and soil was classified through a sieve analysis test in order to perform grain size analysis and a specific gravity test for an indoor test. The principle of FFPT is that the penetration needle installed at the tip of an object put into free fall using gravity is used to measure the depth of penetration into the road surface after subgrade or roadbed compaction has been completed; the degree of compaction is obtained through the unit weight of soil test according to the sand cone method and the relationship between the degree of compaction and the depth of the penetration needle is verified. The maximum allowable grain size of soil is 2.36 mm. For $A_1$ compaction, a trend line was developed using the result of the test performed from a drop height of 10 cm, and coefficient of determination of the trend line was $R^2=0.8677$, while for $D_2$ compaction, coefficient of determination of the trend line was $R^2=0.9815$ when testing at a drop height of 20 cm. Free fall test was carried out with the drop height adjusted from 10 cm to 50 cm at increments of 10 cm. This study intends to compare and analyze the correlation between the degree of compaction obtained from the unit weight of soil test based on the sand cone method and the depth of penetration of the penetration needle obtained from the FFPT meter. As such, it is expected that a portable penetration tester will make it easy to test the degree of compaction at many construction sites, and will lead to a reduction in time, equipment, and manpower which are the disadvantages of the current degree of compaction test, ultimately contributing to accurate and simple measurements of the degree of compaction as well as greater economic feasibility.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.299-306
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• 2016

In this research, influence of low quality aggregate on engineering properties of concrete was evaluated experimentally. From the experiment, the fresh properties of slump and air content were controlled with unit water and AE dosage and all mixture were designed to have similar fresh properties of slump and air content with various quality of aggregate. Under this conditions, comparing with the mixture with high quality aggregate, the mixture with low quality aggregate showed the unit water and AE dosage were increased about 18 and 98%, respectively, because of poor grading and quantity of fines. For compressive strength, the low quality aggregate, specifically, exploded debris, clay sand, and sea sand contributed on decreasing compressive strength about 20~35%. Additionally, the concrete mixture including low quality fine and coarse aggregate showed adverse quality in not only compressive strength but also durability of freeze-thawing resistance, drying shrinkage, carbonation, and chloride ingression. Therefore, it is considered that for low quality aggregate, extra treatment processes such as washing or controlling gradation, and regulation to limit the use of low quality aggregate are needed.