• Journal of Ocean Engineering and Technology
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• v.26 no.5
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• pp.31-39
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• 2012

Anchors are primarily designed and constructed to resist outwardly directed loads imposed on the foundation of a structure. These outwardly directed loads are transmitted to the soil at a greater depth by the anchors. Buried anchors have been used for thousands of years to stabilize structures. Nowadays, various types of earth anchors are used for the uplift resistance of transmission towers, utility poles, submerged pipelines, and tunnels. Anchors are also used for the tieback resistance of earth-retaining structures, waterfront structures, at bends in pressure pipelines, and when it is necessary to control thermal stress. In this research we analyzed the uplift behavior of plate anchors in sand using a laboratory experiment to estimate the uplift behavior of plate anchors under various conditions. To achieve the research purpose, the uplift resistance and displacement characteristics of plate anchors caused by the embedment ratio, plate diameter, and loading rate were studied, compared, and analyzed in various cases.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.429-438
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• 2019

Microbially induced carbonate precipitation (MICP) is an innovative soil improvement approach utilizing metabolic activity of microbes to hydrolyze urea. In this paper, the shear response and the erodibility of MICP-treated sand under axial compression and submerged impinging jet were evaluated at a low confining stress range. Loose, poorly graded silica sand was used in testing. Specimens were cemented at low confining stresses until target shear wave velocities were achieved. Results indicated that the erodibility parameters of cemented specimens showed an increase in the critical shear stress by up to three orders of magnitude, while the erodibility coefficient decreased by up to four orders of magnitude. Such a trend was observed to be dependent on the level of cementation. The treated sand showed dilative behavior while the untreated sands showed contractive behavior. The shear modulus as a function of strain level, based on monitored shear wave velocity, indicated mineral debonding may commence at 0.05% axial strain. The peak strength was enhanced in terms of emerging cohesion parameter based on utilizing the Mohr-Coulomb failure criteria.

• Journal of Species Research
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• v.10 no.3
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• pp.262-266
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• 2021

In this study, three lecanid rotifer species were newly recorded in Korea: Lecane inermis (Bryce, 1892), L. furcata (Murray, 1913), and L. nana (Murray, 1913). Most of the lecanid rotifers recorded in Korea have been collected from stagnant water, and Lecane furcata and L. nana were collected from a reservoir. In contrast, L. inermis was found in a soil sample. Lecane inermis is the first illoricated lecanid species reported in Korea. This species is distinguished from other illoricated species by its toes with relatively long claws. Lecane furcata is the most common lecanid rotifer in submerged vegetation. The morphological characteristics of its lorica are similar to many other lecanid rotifers, but it can be distinguished by its completely fused toes with a terminal fissure, an absence of antero-lateral spines, and the ratio of lorica/toe length. Lecane nana is most similar to L. tryphema Harring & Myers, 1926, but can be distinguished by the toe tips curved outwards. The three species in this study are considered to have a cosmopolitan distribution and have been recorded in many Asian countries. In this paper, we describe the morphological characteristics of the three lecanid species with trophi structures observed by scanning electron microscope.

• Corrosion Science and Technology
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• v.21 no.1
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• pp.1-8
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• 2022

The use of cathodic protection for metals can be achieved by sacrificial anode CP or impressed current CP, or a combination of both. Cathodic protection is a highly effective anti-corrosion technique for submerged metals or metals in soil. But because the non-immersion atmospheric automobile environment is a high resistance environment, it is limited by fundamental cathodic protection. However, the application of cathodic protection to automobiles is attractive because of the possibility of maintaining corrosion resistance while using lower-cost materials. A commercially available product for automobiles that uses both sacrificial anode CP and impressed current CP was tested in a periodic salt spray environment to investigate the performance of the devices. Experimental results show that the metal to be protected has different anti-corrosion effects depending on the distance from the anode of the device, but it is effective for the entire 120 cm long specimen exposed with one anode. The cathodic protection is effective because the conductive tape attached to the anode of the structure to be protected acts as a constant electrolyte in wet and dry conditions. The results show that the entire standard passenger car can be protected by cathodic protection with 4 anodes.

• Korean Journal of Soil Science and Fertilizer
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• v.16 no.4
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• pp.372-381
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• 1983

A laboratory experiment was performed to investigate the effects on redox potential of submerged soil by application of CNP herbicide (2, 4, 6-Trichlorophenyl-4-Nitrophenyl ether) with or without rice straw. Two soils, sandy loam and clay loam textured, were incubated for sixty days at a constant temperature, $25^{\circ}C$. Sampling and analysis of pH, Eh and nitrogen mineralization were carried out during the incubation. The results were summarized as follows. 1. The CNP application decreased redox potential and increased soil pH. The higher the concentration of applicated CNP was, the effects on soil Eh and pH were higher. When rice straw was used with CNP, the Eh of soil remarkably decreased, but seperating the individual effects of rice straw and CNP was impossible in this study. 2. Ammonification increased as the concentration of applied CNP increased regardless of rice straw application or not. It was higher in sandy loam soil than clay loam soil. 3. Nitrification decreased as the concentration of applied CNP increased, especially in the sandy loam soil. Rice straw application reduced nitrification.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.1
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• pp.93-101
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• 2017

In this study, the microbubbles were applied to the MBR process for night soil treatment, and the removal efficiency was estimated. As a result of the this study, when the microbubble was supplied directly to the aerobic tank in which the membrane was submerged, excessive scum was generated so could not stable operation of the process. The SS removal efficiencies in the pre-treatment tank were 74.3%, 82.8%, 75.0%, 52.1% on average at the 2 kg, 4 kg, 6 kg, and $8kg\;COD_{Cr}/m^3$, respectively. The mean removal efficiencies were more than 99.4%, 94.0%, 74.1% for SS, $TCOD_{Cr}$, $SCOD_{Cr}$ by MBR process. On the other hand, when the microbubble are directly supplied to the aerobic tank, the microbubble and the scum are attached each other to accelerate the fouling. Therefore, it can be confirmed that stable treatment can be achieved by applying microbubble to the front of the bioreactor for removal of SS and oxidation of organic matters in high concentration organic wastewater treatment such as night soil.

• Journal of Environmental Impact Assessment
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• v.16 no.2
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• pp.143-156
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• 2007

This study has researched the management status and the pollution level of water, soil, stream sediments of 11 abandoned coal mines out of a total of 12 within Obong-Dam area except Bukyung mine, which was submerged when constructing Obong-Dam, and selected areas which are in needs to have pollution control facilities in the first place. From the results of examination on the runoff at the waste rock pile and mineheads, the runoff from Sueun mine (pH, Fe, Al), Samwon mine (pH, Al), Wangdo mine (pH, Al), Mose mine (pH, Fe, Al) and Daeryeong mine (pH) exceeded the permissible discharge standards of the water quality, but the water at merging point with Obong-Dam after joined with Doma branch satisfied both Water Quality Standards and Drinking Water Quality Standards. In regard to groundwater contamination, it is found that areas where exceeded the Drinking Water Quality Standards are Wangdo mine (pH), Jangjae mine (pH, Zn), Daeryeong mine (pH) whereas all areas satisfied Soil Contamination Warning Standards of Soil Environmental Conservation Law. When comparing a research result on underwater sediments of branches of abandoned mines to the EPA Guidelines for classification of great lakes harbor sediments, Dongguk Gaerim (Fe), Jungwon mine (Fe), Daebo mine (Mn), Samwon mine (Mn) and Daeryeong mine (Mn) showed mid-level of contamination, whereas Sueun (Fe, Mn), Daebo mine (Fe), Woosung mine (Fe, Mn), Wangdo mine (Fe, Mn), Mose mine (Fe) and Daeryeong mine (Fe) showed high-level of contamination. In addition, contamination levels of underwater sediments in Wangsan and Doma branch where abandoned mine's branches merge together, Wangsan branch showed no contamination at all whereas Doma branch shows mid-level of contamination which reflect the Doma branch is affected by waste rock pile and minehead runoff of the abandoned mines in the Doma branch area. It is concluded that Mose mine and Sueun mine required treatment of acid mine drainage. and Wangdo, Jungwon, and Samwon mines were in need of mine tailing and erosion control work. The Samwon mine additionally required a control system for closed minehead runoff. Although the Samwon mine reached a high concentration of Al, Mn $Ca^{2+}$, $SO{_4}^{2-}$ in the runoff, the levels decreased after it was combined with a tributary. It has been concluded that after further monitoring of the cause of pollution, a preventive measure system may be needed to be built.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.6
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• pp.499-505
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• 1992

This experiment was carried out to find out the optimum application method of slow-release fertilizer under different soil textures, clay loam(Deogpyeong series), sandy loam (Gangseo series) in the southern region(Milyang, Kyeongnam) of Korea. The fertilizers used were Chosun slow-release fertilizer(silicate latex coated fertilizer: N-P$_2$O$_{5}$-K$_2$O=18-12-13) and Meister 15 (thermoplastic resin coated fertilizer : N-P$_2$O$_{5}$-K$_2$O=14-14-14). The two whole basal application methods such as side band placement at transplanting time of rice plant(cv.Donghaebyeo) and incorporation with soil as basal were tested. The released amount of ammonium nitrogen from the soils for 4 days submerged was 95ppm in sandy loam and 60ppm in clay loam. The greenish degree of rice leaf was higher at the whole plow layer placement method than the others. The nitrogen efficiencies of the fertilizers were Meister 15 > convention > Chosun in order and between the application methods were similiar. The growth status was better at the whole plow layer placement application method of Meister 15 regardless of soils and seedling ages. The ripening ratio was increased at slow-release fertilizer application, and between application methods, whole plow layer placement was lower because of lodging damage. The yield in clay loam soil showed a significant difference between the ferilizers, but there were slight differences between the application methods and fertilizers in sandy loam soil. As a result, the slow-release fertilizer, Meister 15, applied at the whole layer showed a good rice growth and seemed a plausible fertilizing method.

• Journal of the Korean Geophysical Society
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• v.5 no.1
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• pp.9-18
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• 2002

We performed a long-term monitoring of self-potential(SP) using the Cu-CuSO₄non-polarizable electrode and copper-clad electrodes(CCE) in a test site in order to analyze the effects of surrounding environmental noises such as temperature, rainfall and soil moisture content on the electrodes. Analysis of the temperature dependence of the non-polarizable electrodes showed that is temperature coefficient was about +0.5 mV/°Fwhen its end was exposed to atmosphere while it was less than +0.5 mV/℃ when submerged into the subsurface, which reflects that there exists an 8 to 11 hour lag between temperatures at the depth of 15 cm and atmosphere. CCE was independent of atmospheric temperature in subsurface but showed temperature coefficient of 1.0 mV/℃ when exposed to atmosphere. Drifts of 1 to 2 mV recorded with the non-polarizable electrode directly related to the soil moisture content when it was buried in subsurface. Drift with CCE also showed similar trend to the soil moisture content, and 5 mV drift was recorded according to 5% of daily variation. The soil moisture content had strong effects on the measurement with CCE in rainfall since the flow potential is generated on the surface of the electrode.

• Journal of the Korean Geotechnical Society
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• v.38 no.5
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• pp.5-17
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• 2022

A pile is a type of medium for constructing superstructures in weak geotechnical conditions. A pretensioned spun high-strength concrete (PHC) pile is composed of high-strength concrete with a specified strength greater than 80 MPa. Therefore, it has advantages in resistance to axial and bending moments and quality control and management since it is manufactured in a factory. However, the skin friction of a pile, which accounts for a large portion of the pile bearing capacity, is only approximated using empirical equations or standard penetration test (SPT) N-values. Particularly, there are some poor research results on the pile-soil interface under the seismic loads in Korea. Additionally, some studies do not consider geoenvironmental elements, such as groundwater pH values. This study performs sets of cyclic simple shear tests using submerged concrete specimens for 1 month to consider pH values of groundwater and clay specimens composed of kaolinite to generate a pile-soil interface. 0.2 and 0.4 MPa of normal stress conditions are considered in the case of pH values. The disturbed state concept is employed to express the dynamic behavior of the interface, and the disturbed function parameters are newly suggested. Consequently, the largest disturbance increase under basic conditions is observed, and an early approach to the failure under low normal stress conditions is presented. The disturbance function parameters are also suggested to express this disposition quantitatively.