• Journal of the Korean Geosynthetics Society
• /
• v.6 no.3
• /
• pp.17-23
• /
• 2007

To construct an ideal geosynthetic reinforced soil retaining wall (GRS-RW), the facing of the wall should be flexible enough to accommodate a large deformation of the supporting ground and to develop the large tensile force in reinforcements during wall construction as long as the stability is ensured, but should be rigid enough to be stiff and stable as well as durable and aesthetically acceptable for a long life time when the wall is in service. Facing conditions during the construction and service of the wall are quite different. So it is difficult to be satisfied all these conditions with the current construction method which is mainly used in reinforced wall construction in Korea. Most of this contradiction could be solved by the staged construction procedure. According to the results of cases and references analyses, stage construction procedures make it possible to accommodate large deformation of the supporting ground and backfill without losing the stability of the wall, and to derive the tensile strength of reinforcement causing deformation of the facing. When the facing is a full-height rigid one, it also appeared almost impossible to occur a local shear failure of the active zone, and pull-out failure of reinforcements. Therefore, GRS-RWs having a full-height rigid facing have been constructed by the staged construction procedures that matched well with the theory of reinforced soil, which had outstanding stability and durability, and thus could be used for railways and bridge abutments in Korea in the future.

• Journal of Korean Society for Geospatial Information Science
• /
• v.19 no.1
• /
• pp.21-28
• /
• 2011

Site conditions affect the magnitude of loss due to geologic hazards including, but not limited to, earthquakes, landslides and liquefaction. Reliable geologic loss estimation system requires site information which can be achieved by GIS-based method using geologic or topographic maps. Slope data derived from DEM can be an effective indicator for classifying the site conditions. We studied and discussed the effect of different DEM resolutions in the site classification. We limited the study area to the south-eastern Korea and used two different resolutions of DEMs to observe discrepancies in the site classification results. Largest discrepancy is observed in the areal coverage of site class C(very dense soil and soft rock) and E(soft soil). Comparison of results shows that more areas are classified as site class B(general rock) or E(soft soil) when we use higher resolution DEM. The comparison also shows that more areas are classified as site class C or D(stiff soil) using lower resolution DEM. The comparison of results using resampled DEMs with different resolutions shows that the areal coverage of site class B and E decreases with decreasing resolutions. On the contrary, areal coverage of site class C and D increase with decreasing resolutions. Loss estimation system can take advantage of higher-resolution DEMs in the area of rugged or populated to obtain precise local site information.

• Korean Journal of Plant Resources
• /
• v.35 no.1
• /
• pp.29-35
• /
• 2022

Elsholtzia byeonsanensis is a Korean native plant of the Lamiaceae family, and was first introduced in the Korean Journal of Plant Taxonomy. This plant has a short plant length of 20-35 cm, with leathery and glossy leaves. The purple flowers bloom in November, so they are highly useful as potted or ground cover ornamental plants. In this study, tray cell size (128, 162, and 200-cell trays), soil composition [horticultural soil (HS): decomposed granite (DG) 1:1, 1:2, and 1:4 (v:v)], seeding rate (1, 2, and 3 seeds per cell) and additional fertilizer concentrations (0, 250, 500, and 1000 mg/L Hyponex) were tested to find out the optimum seedling growth conditions. As a result of the study, E. byeonsanensis growth increased proportionally as the cell size of the tray increased. The growth was inhibited as the percentage of DG increased. As for the growth according to the seeding rate, plant height, plant width, leaf length, and leaf width decreased as the seeding rate increased, but there was no difference in the number of leaves, stem diameter, and root length. There was an increasing trend in seedling growth as the additional fertilizer concentration increased. Therefore, for producing E. byeonsanensis seedling, it is most effective to fill HS or HS:DG 1:1 in 128-cell trays, sow one seed per cell, and spray the seedling at 1000 mg/L for additional fertilizer.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.3
• /
• pp.268-274
• /
• 2010

The properties of upland soils are much more dependent upon topography than those of paddy soils, and they give us very useful information to manage the upland fields. Therefore, we investigated the selected physical and chemical properties of upland soils at 84 and 150 topographic sampling sites, respectively. The topographic sites included 34.7% of local valley and fans, 18.7% of hilly and mountains, 20.0% of mountain foot slopes, 14.0% of alluvial plains, 8.0% of diluvium, and 4.6% of fluvio-marine deposits. Based on the investigation, soil textures in Jeonbuk upland fields were mostly sandy loam, sandy clay loam, clay loam, and clay soils, especially sandy clay loam soils were evenly distributed in all of the topographic sites. Soil slopes in the sites ranged from 0 to 15%, which showed an optimal condition for farm land. Soil bulk density and compaction values were from 1.19 to 1.24 g $cm^{-3}$ and from 12.1 to 13.9 mm, respectively. As comparing with the optimal conditions of soil chemical properties for upland soils proposed by National Institute of Agricultural Science and Technology, Korea, 37%, 42.7%, 93.0% of the sites were within optimum levels with soil pH, content of soil organic matter, and electrical conductivity, respectively. However, 64.0%, 47.3%, 48.7%, and 42.7% of the upland soils contained excess levels of exchangeable K, Ca, and Mg, and available phosphorus, respectively. In addition, the contents of heavy metals, As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, in the Jeonbuk upland soils were much less than threshold levels.

• The Korean Journal of Ecology
• /
• v.25 no.1
• /
• pp.9-17
• /
• 2002

Human activities greatly affect the environment causing its degradation. Urban development and road networks construction cause main impacts on ecosystems and particularly on vegetation cover: road constructions induce complete degradation of the vegetation cover and often leaves a hare land, sometimes without even a soil cover. Reconstitution of vegetation cover is necessary to limit superficial erosion and land slipping on the road, towards a reintegration of the site in the neighbouring landscape. Many approaches have been studied over the last 30 years aiming at this reconstitution of vegetation cover. At frost, the main purpose of land reclamation was to create a new ecosystem. At this time, the environment created was rather a "garden" with a new soil adapted to the plantation of "decorative" species. Then, in early 90′s many studies on the restoration ecology concept rather focused on adapting the vegetation to the existing conditions on the site, as in a side road embankment for example. Nowadays, we notice a large tendency towards the use of such adapted native species instead of industrially produced seeds. In southern France, our team have led research on the potentials of those local species for their use in revegetation processes with hydro-seeding. We therefore developed an approach combining the use of different types of species: Industrially produced, native and wild cultivated species. This method integrates the benefits of using available low costing seeds that are already used on large scale projects with better adapted species, issued form the cultivation of native species and seed production for their use on smaller scale and more costly but more effective results. The use of wild cultivated species seeds was developed in order to limit the cost and reduce harsh natural seed withdrawal in the natural environment In the case of the use of native species. Besides, the use of such seeds allowed a larger geographical scale of use than with local native seeds. In addition, our team began two years ago a research project in Lebanon aiming at the Introduction and development of the revegetation techniques in Lebanon. In fact, this country bared since 20 years the consequences of urban pressure on its environment especially by the development of quarries and road networks. Therefore, pioneer work is necessary to aim at the adaptation of these techniques to the local environment.

• Journal of Plant Biotechnology
• /
• v.36 no.1
• /
• pp.18-22
• /
• 2009

This work was conducted to establish an efficient plant regeneration system for genetic transformation and the in vitro conservation of Sedum sarmentosum genetic resources. Effects of glutamine and $AgNO_3$ on plant regeneration between two genotypes were investigated using MS media supplemented with 0.2 mg/L NM and 3.0 mg/L BA. Calluses were formed on leaf explants placed on MS solid media supplemented with 3 mg/L 2,4-D and 1 mg/L BA. Calluses of Keumsan local strain produced shoots at a frequency of up to 100% after 50 days of culture on medium supplemented with glutamine. The highest number of shoots per callus was 17.6 at 350 mg/L glutamine. However, calluses of Wanju local strain gave rise to no shoots under the same culture conditions. Likewise, calluses of Keumsan local strain produced shoots at a frequency of up to 100% after 50 days of culture on medium supplemented with $AgNO_3$ whereas Wanju local strain sporadically produced shoots. The highest number of shoots per callus of Keumsan local stain was 16.1 at $15{\mu}M$ $AgNO_3$. Regenerated shoots were subcultured on hormone-free MS medium for rooting and shoot growth, and then 3-5 cm high plantlets were transplanted to the artificial soils comprising vermiculite and perlite, where they survived at a frequency of 88-100%. After being transplanted into upland soil:sand (1:1, v/v) in a greenhouse, regenerated plants showed a morphologically normal growth.

• Geomechanics and Engineering
• /
• v.12 no.5
• /
• pp.849-862
• /
• 2017

With growing interests in using bacterial biopolymers in geotechnical practices, identifying mechanical properties of soft gel-like biopolymers is important in predicting their efficacy in soil modification and treatment. As one of the promising candidates, dextran was found to be produced by Leuconostoc mesenteroides. The model bacteria utilize sucrose as working material and synthesize both soluble and insoluble dextran which forms a complex and inhomogeneous polymer network. However, the traditional rheometer has a limitation to capture in situ properties of inherently porous and inhomogeneous biopolymers. Therefore, we used the particle tracking microrheology to characterize the material properties of the dextran polymer. TEM images revealed a range of pore size mostly less than $20{\mu}m$, showing large pores > $2{\mu}m$ and small pores within the solid matrix whose sizes are less than $1{\mu}m$. Microrheology data showed two distinct regimes in the bacterial dextran, purely viscous pore region of soluble dextran and viscoelastic region of the solid part of insoluble dextran matrix. Diffusive beads represented the soluble dextran dissolved in an aqueous phase, of which viscosity was three times higher than the growth medium viscosity. The local properties of the insoluble dextran were extracted from the results of the minimally moving beads embedded in the dextran matrix or trapped in small pores. At high frequency (${\omega}>0.2Hz$), the insoluble dextran showed the elastic behavior with the storage modulus of ~0.1 Pa. As frequency decreased, the insoluble dextran matrix exhibited the viscoelastic behavior with the decreasing storage modulus in the range of ${\sim}0.1-10^{-3}Pa$ and the increasing loss modulus in the range of ${\sim}10^{-4}-1\;Pa$. The obtained results provide a compilation of frequency-dependent rheological or viscoelastic properties of soft gel-like porous biopolymers at the particular conditions where soil bacteria produce bacterial biopolymers in subsurface.

• Journal of Environmental Health Sciences
• /
• v.40 no.1
• /
• pp.27-37
• /
• 2014

Objectives: On September 27, 2012, leakage of anhydrous hydrofluoric acid occurred in a chemical plant in the Gumi National Industrial Complex. Following the accident, local factory workers and residents complained of abnormal health conditions. In addition, visual discolorations were widely observed in crops and trees in surrounding areas. The main objectives of the present study were to identify the area that was affected by the spill using data obtained from plants, soil, and water samples after the accident. Methods: Fluoride concentrations were analyzed in pine tree needles, soil, nearby streams, ponds and reservoirs collected from an area within a radius of three kilometers from the plant where the leak occurred. Fluoride concentrations in the air at the time of leakage were then estimated from fluoride concentrations that were measured in the pine tree needles. A Kriged map was developed to describe the spatial distribution of hydrofluoric acid at the time of the leakage and was compared with the area designated as a Special Disaster Zone by the government. Results: The Special Disaster Zone did not include all the affected area that was estimated by the Kriged map. Analytical results of the environmental samples also supported this discrepancy. Conclusion: Using plants, atmospheric concentrations of fluoride at the time of the leakage could be estimated. For the area that was identified as affected, further public health risk assessment and environmental risk assessment should be considered. Also, in the absence of air monitoring at the time of leakage, studies employing plants may be conducted in order to better understand the spatial extent and severity of the contamination.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.563-574
• /
• 2008

Most of earthquake-induced geotechnical hazards have been caused by the site effects relating to the amplification of ground motion, which are strongly influenced by the local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated GIS-based information system for geotechnical data, called geotechnical information system (GTIS), was constructed to establish a regional counterplan against earthquake-induced hazards at an urban area, Daejeon, which is represented as a hub of research and development in Korea. To build the GTIS for the area of interesting, pre-existing geotechnical data collections were performed across the extended area including the study area and a walk-over site survey was additionally carried out to acquire surface geo-knowledge data. For practical application of the GTIS used to estimate the site effects at the area of interesting, seismic microzoning map of the characteristic site period was created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation for site classification according to the spatial distribution of the site period was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site in the study area. Based on the case study on seismic zonations at Daejeon, it was verified that the GIS-based GTIS was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.311-314
• /
• 2006

This paper concerns about total dynamic analysis of integrated mining system. This system consists of vertical steel pipe, intermediate buffer station, flexible pipe and self-propelled miner. The self-propelled miner and buffer are assumed as rigid-body of 6-dof. Discrete models of vertical steel pipe and flexible pipe are adopted, which are obtained by means of lumped-parameter method. The motion of mining vessel is not considered. Instead, the motion of mining vessel is taken into account in form of various boundary conditions (e.g. forced excitation in slow motion and/or fast oscillation and so on). A terramechanics model of extremely soft cohesive soil is applied to the self-propelled miner. The hydrodynamic forces and moments are included in the dynamic models of vehicle and lifting pipe system. Hinged and fixed constraints are used to define the connections between sub-systems (vertical steel pipe, buffer, flexible pipe, miner). Equations of motion of the coupled model are derived with respect to the each local coordinates system. Four Euler parameters are used to express the orientations of the sub-systems. To solve the equations of motion of the total dynamic model, an incremental-iterative formulation is employed. Newmark-b method is used for time-domain integration. The total dynamic responses of integrated mining system are investigated.