• Journal of Forest and Environmental Science
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• v.35 no.1
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• pp.31-40
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• 2019

Daphne pseudomezereum var. koreana is an endangered deciduous shrub distributed in mountain areas that is vulnerable to climate change. The purpose of this study was to provide foundational data on the physical characteristics, soil environment, and vegetation structure of habitats of Daphne pseudomezereum var. koreana habitat in Korea in order to help with management decisions on ecosystem restoration. Rock exposure was 15 to 35%, with an average of 24%. The native habitat of D. pseudomezereum included 129 taxa consisting of 46 families and 95 genera. Two-way cluster analysis divided the habitat into three plant communities: Community I (dominaterd by Tilia amurensis and Quercus mongolica), Community II (dominaterd by Fraxinus rhynchophylla and Acer pseudosieboldianum), and Community III (dominaterd by Ulmus davidiana var. japonica). The diversity indices for Communities I, II, and III were 1.124, 1.047 and 0.932, respectively. The soils were loam or clay loam. Soil pH, organic matter content, and available phosphoric acid were 5.40, 14.38%, and 31.08 ppm, respectively. Ordination analysis resulted that most significant factors influencing D. pseudomezereum distribution were magnesium content of soil, shrub layer, and altitude.

• Journal of Forest and Environmental Science
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• v.34 no.6
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• pp.429-434
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• 2018

Extractable iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) contents and their distribution with depths in soils of forested and adjacent deforested areas at Jahazpura, Teknaf, Cox's Bazar of Bangladesh were studied. The soils under forest showed higher levels of DTPA-extractable micronutrients in all three layers of soil in comparison to those of the deforested areas. The differences between forested and deforested sites were, in most cases, significant.. The top soils of forested sites had the higher contents of micronutrient and generally decreased with depth in forested soils, while there was no regular trend of distribution in deforested soils. The study also revealed that contents of extractable Fe, Mn and Cu were sufficient in all depths and sites but Zn was deficient in bottom layer of forested and all three layers of deforested sites. The results suggested that organic matter, clay and soil pH could play important roles in concentrations and distributions of micronutrients in soils of the study areas.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.1097-1107
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• 2020

Assessment of soil carbon stock is essential for climate change mitigation and soil fertility. The digital soil mapping (DSM) is well known as a general technique to estimate the soil carbon stocks and upgrade previous soil maps. The aim of this study is to calculate the soil carbon stock in the top soil layer (0 to 30 cm) in Jeolla Province of South Korea using the DSM technique. To predict spatial carbon stock, we used Cubist, which a data-mining algorithm model base on tree regression. Soil samples (130 in total) were collected from three depths (0 to 10 cm, 10 to 20 cm, 20 to 30 cm) considering spatial distribution in Jeolla Province. These data were randomly divided into two sets for model calibration (70%) and validation (30%). The results showed that clay content, topographic wetness index (TWI), and digital elevation model (DEM) were the most important environmental covariate predictors of soil carbon stock. The predicted average soil carbon density was 3.88 kg·m-2. The R2 value representing the model's performance was 0.6, which was relatively high compared to a previous study. The total soil carbon stocks at a depth of 0 to 30 cm in Jeolla Province were estimated to be about 81 megatons.

• Korean Journal of Materials Research
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• v.31 no.11
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• pp.608-613
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• 2021

This study investigated the reaction between clay and Mn. Mn was coated using a manganese sulfate on porcelain plate and sintered from 1,100 ℃ to 1,250 ℃. The body begin to shrink around 950 ℃ with the increase in temperature and rapidly progressed after 1,100 ℃. Shrinkage of celadon body was performed at a lower temperature than for other substrates. Quartz, kaolin, and feldspar were the main crystalline phases of the starting materials, but they became mullite and crystobalite during the firing process, and some formed amorphous glass. When manganese sulfate was applied and fired, manganese oxide was fused, and some manganese oxide reacted with the substrate to show a dense microstructure different from that of the substrate; the substrate had pores. The manganese coated porcelain fired at 1,200 ℃ had L^* values of 55.25, 36.87, and 37.13 for the white ware, celadon body, and white mixed ware, respectively; with a^* values of 4.63, 3.07, and 2.15, and b^* values of 7.93 and 3.98, it was found to be 3.42. This result indicated that the color of the surface was affected during firing by the chemical reaction between the substrate and manganese.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.497-508
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• 2006

Busan-Geoje Fixed Link, total length of 8.2km, consist of bridge and immersed tunnel connects Gaduk island, Busan and Jangmokmyon, Geoje, in extension of the $58^{th}$ local road. The immersed tunnel, a total length of 3.7km within Busan-Geoje Fixed Link, was planed first timein domestic but the deep water depth like maximum of 50m with offshore conditions and the 35m thickness of soft clay layer under the immersed tunnel, migth be some problems like the differential settlement during or after works. So it was designed to install SCP(Sand Compaction Pile) column partially to improve the soft ground under the immersed tunnel. In this paper, it is presented to illustrate the design including ground condition under the immersed tunnel, improvement design, upheaval shape and ratio due to SCP test construction.

• Geomechanics and Engineering
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• v.34 no.5
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• pp.561-575
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• 2023

This study investigates to provide a fast solution to the problem of bearing capacity in layered soils with easily obtainable parameters that does not require the use of any charts or calculations of different parameters. Therefore, a hybrid approach including both the finite element (FE) method and machine learning technique have been applied. Firstly, a FE model has been generated which is validated by the results of in-situ loading tests. Then, a total of 192 three-dimensional FE analyses have been performed. A data set has been created utilizing the soil properties, footing sizes, layered conditions used in the FE analyses and the ultimate bearing capacity values obtained from the FE analyses to be used in multigene genetic programming (MGGP). Problem has been modeled with five input and one output parameter to propose a bearing capacity formula. Ultimate bearing capacity values estimated from the proposed formula using data set consisting of 20 data independent of total data set used in MGGP modelling have been compared to the bearing capacities calculated with semi-empirical methods. It was observed that the MGGP method yielded successful results for the problem considered. The proposed formula provides reasonable predictions and efficient enough to be used in practice.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.175-176
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• 2023

The masonry structure is constructed by cement mortar binding material of brick objects and uses reinforced hardware(connected hardware or wall tie) together when building. However, over time, the corrosion of reinforced steel and the deterioration of joint mortar as well as bricks cause the risk of collapse. In particular, when the externally decorated brick wall is installed on the concrete girder for each floor, the angle bracket is not constructed or corroded, the full-layer weight load is applied to the wall of 0.5B, which is an example of full-scale or collapse. As a result of the evaluation, it was confirmed that the performance was improved compared to the existing bracket, and we plan to carry out a real-life test and long-term performance review of the building using the bracket in the future.

• Geomechanics and Engineering
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• v.35 no.4
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• pp.385-393
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• 2023

To analyze the consolidation with horizontal sand drains, the plane strain consolidation model under multi-ramp loading is established, and its corresponding analytical solution is derived by using the separation of variables method. The proposed solution is verified by the field measurement data and finite element results. Then, the effects of the loading mode and stress distribution on consolidation and dissipation of pore pressure are investigated. At the same time, the influence of hydraulic conductivity and thickness of sand blankets on soil consolidation are also analyzed. The results show that the loading mode has a significant effect on both the soil consolidation rate and generation-dissipation process of pore water pressure. In contrast, the influence of stress distribution on pore pressure dissipation is obvious, while its influence on soil consolidation rate is negligible. To guarantee the fully drained condition of the sand blanket, the ratio of hydraulic conductivity of the sand blanket to that of clay layer k_d/k_v should range from 1.0×10⁴ to 1.0×10⁶ with soil width varying from 100 m to 1000 m. A larger soil width correspondingly needs a greater value of kd/kv to make sure that the pore water can flow through the sand blanket smoothly with little resistance. When the soil width is relatively small (e.g., less than 100 m), the effect of thickness of the sand blanket on soil consolidation is insignificant. And its influence appears obvious gradually with the increase of the soil width.

• Journal of Soil and Groundwater Environment
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• v.28 no.5
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• pp.68-77
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• 2023

The effect of soil damage on the physicochemical characteristics and activity of the soil microbial community is not well known. This study investigates this relationship by analyzing 11 soil samples collected from various points of soil damage across Gyeonggi-do. Soil damage resulted from forest fires, landslides, and development areas, with their impacts most severe on the topsoil layer (0-30 cm). Dehydrogenase and β-glucosidase activities were notably higher at locations damaged by forest fires compared to other sites. While enzyme activities in soils influenced by landslides and development areas were relatively low, sites with a pollution history exhibited elevated dehydrogenase activity, likely due to past microbial response to the pollution. Additionally, an assessment of carbon substrate usability by soil microorganisms indicated higher substrate availability in areas impacted by forest fires, contrasting with lower availability in landslide and development sites. Statistical analysis revealed a positive correlation between organic content of sand and clay and microbial activity. These findings provide valuable insights into soil damage and associated restoration research, as well as management strategies.

• Korean Journal of Soil Science and Fertilizer
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• v.6 no.3
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• pp.141-152
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• 1973

The mineralogical studies of the eleven sub-soil samples derived from granite, granodiorite, diorite and arkose sandstone, taken from apple orchards in the province of Kyungsangbukdo, Korea are made to investigate the relationships between the mineral weathering, soil forming processes and mineralogical composition. The fine sand fraction (less than 0.2mm) and the clay fraction (less than 2 micron) are dispersed with the shaker after hydrogen peroxide treatment for the removal of organic matter, and separated from each suspension by gravity sedimentation. The fine sand are observed by mineral microscope and the clay are observed by X-ray diffraction patterns, differential thermal analysis curves and infrared spectrum. The outline of the results are as follows. 1. The primary minerals ; Quartz, changed-feldspar, plagioclase, alkali-feldspar are dominant in almost all samples, and some samples contain an appreciable amount of hornblende, biotite, muscovite and plant opal. There are also those samples which contain very small quantity of pyroxene group, tourmaline, epidote, cyanite, magnetite, volcanic glass and zircon. They are mainly derived from weathering products of granite, granodiorite, diorite, arkose or its mixtures. 2. All samples contain expanding or nonexpanding $14{\AA}$ minerals, illite and kaolin minerals, and some samples contain chlorite, cristobalite, gibbsite, and those primary minerals as quartz and feldspar, but the quantities vary according to the parent matrials. 3. Non-expanding $14{\AA}$ minerals may be dioctahadral vermiculite which sandwiches gibbsite layer or chlorite in between layer lattices. 4. As for clay minerals, montmorillonite was principal component in the samples derived from weathering products of arkose sandstone and tertiary. Minerals which are derived from weathering products of arkose have kaolin minerals and vermiculite as their principal component, and minerals derived from weathering products of acidic rock group are generally classified into two groups, the kaolin mineral group, and the kaolin minerals and vermiculite group.