• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.3
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• pp.35-45
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• 2003

This study was performed to suggest growth status data of the large old trees as the natural monuments of Korea. Field investigation of 70 large old trees as the natural monuments of Korea was carried out in Seoul, Inchon, Kyungki, Chungbuk, Chungnam, Chonbuk, Chonnam. The main field of this study is classified into the growth condition, soil state and management situation. The results of this study are below : The age distribution of the large old trees as the natural monuments of Korea is as follows : above l00years in 5.9%, above 200years in 8.9%, above 300 years in 11.8%, above 400 years in 16.2%, above 500 years in 16.2% and above 600years in 41.1%. Location types of the large old trees as the natural monuments of Korea are found in 11 types; the types are hill side(22.9%), historical monument area(15.7%), field(l4.3%) and building area(12.9%), etc. Also, growth type of the trees is individually placed. In the aspect of soil environment, the acidification of soils has been appearing in all surveyed areas, and the soil of Seoul area has much acidum phosphoricum because of excessive fertilizer. Finally, in management situation. major factors inhibiting growth of the large old trees as the natural monuments of Korea are soil covering of protruded root above ground, soil hardening by human, embankments, small area that has been surrounded fence. Continuous monitoring and accumulation of status data are necessary to preserve the large old trees as the natural monuments of Korea.

• Journal of Conservation Science
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• v.25 no.2
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• pp.155-160
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• 2009

This study is designed to optimize the method of using SE-101 for strengthening the durability and the stabilization of moving historical site. The permeability and the shear strength of The epoxy SE-101 with low viscosity were measured on different particle sizes and moisture content of soil. Like it can be expected from the data of viscosity, as the soil particle size was increased, the permeability was also increased, while the shear strength was decreased. And especially, it is noted that the deviation of permeability can be more extreme according to the different hardening speed of macromolecule and mineral additives. As the rate of moisture content in soil sample is increased, the deviation between permeability and shear strength is also increased. Even though among the same soil sample, some parts of it can be weaker than others, which cause the breakages of epoxy products. Thus, it is necessary that the soil should be dried over 50% of permeation depth of SE-101 before use.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.35-44
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• 2007

Plowable fill is generally a mixture of sand, fly ash, a small amount of cement and water. Sand is the major component of most flowable fill mixes. Marine dredged soil was adopted for flowable fill instead of fly ash. Natural sea sand and in-situ soil were used for comparison. The flow behavior, hardening characteristics, and ultimate strength behavior of flowable fill were investigated. The unconfined compression test necessary to sustain walkability as the fresh flowble fill hardens was determined and the strength at 3-days appeared to correlate well with the water-to-cement ratio. The strength parameters, like cohesion and internal friction angle, was determined along the curing time. The creep test for settlement potential was conducted. Also, potable falling weight deflectometer(PFWD) test has been carried out for elastic modulus of each controlled low strength materials(CLSM). The data presented show that marine dredged soil and in-situ soil can be successfully used in CLSM.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.450-457
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• 2020

In this study, engineering characteristics such as flowability, segregation and compressive strength by age to derive fast hardening material mixing proportion using excavated soil. And based on optimal mixing proportion, field simulation experiment conducted in laboratory to examine the effectiveness of the method such as kelly ball drop test and soil penetration test for reviewing the following process. As as a result of evaluation, in case of kelly ball drop test and soil penetration test were securing the following process initiation time 3 hours after place CLSM. As results of these assessments, kelly ball drop test and soil penetration test were applicable for revewing following process in construction field besides unconfined compressive strength method.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.193-203
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• 2021

The time-history finite element analysis is usually used to evaluate the seismic response of shallow foundations. However, the literature lacks studies on the influence of the soil constitutive model complexity on the seismic response of shallow foundations. This study, thus, aims to fill this gap by investigating the seismic response of shallow foundation resting on dry silica sand using the linear elastic (LE) model, elastic-perfectly-plastic (EPP) model, and hardening soil with small strain stiffness (HS small) model. These models have been used because it is intended to compare the results of a soil constitutive model that accurately captures the seismic response of the soil-structure interaction problems (which is the HS small model) with simpler models (the LE and EPP models) that are routinely used by practitioners in geotechnical designs. The results showed that the LE model produces a very small seismic settlement value which is approximately equal to zero. The EPP model predicts a seismic settlement higher than that produced using the HS small model for earthquakes with a peak ground acceleration (PGA) lower than 0.25 g for a relative density of 45% and 0.40 g for a relative density of 70%. However, the HS small model predicts a seismic settlement higher than the EPP model beyond the aforementioned PGA values with the difference between both models increases as the PGA rises. The results also showed that the LE and EPP models predict similar trend and magnitude of the acceleration-time relationship directly below the foundation, which was different than that predicted using the HS small model. The results reported in this paper provide a useful benchmark for future numerical studies on the response of shallow foundations subjected to seismic shake.

• Journal of the Korean Geosynthetics Society
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• v.11 no.2
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• pp.1-9
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• 2012

In order to review the utility of Lade's single hardening constitutive model, a series of isotropic compression-expansion tests and consolidated drained triaxial tests including as CTC, TC, RTC, and OSP were performed by Baekma river sand with various of stress path. Parameters required in model were determined using these tests. The accuracy of analysis was reviewed by back analysis of test results used to determine the 11 parameters of soil property through the test of each stress path. Also. for verifying the accuracy of prediction for the stress-strain behavior using failure criterion related 9 parameters with correlational equation and constant and yield criterion related parameters h, ${\alpha}$ and ${\eta}_1$, when stress path is different with each other, it has been obtained in the review result of stress path dependent characteristics of the constitutional model through the analyzing results of CTC, TC, RTC, OSP, and fine silica sand tests.

• Geomechanics and Engineering
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• v.20 no.1
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• pp.75-86
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• 2020

This study aims to simulate the stabilization process of fibrous peat samples using end-bearing Cement Deep Mixing (CDM) columns by three area improvement ratios of 13.1% (TS-2), 19.6% (TS-3) and 26.2% (TS-3). It also focuses on the determination of approximate stress distribution between CDM columns and untreated fibrous peat soil. First, fibrous peat samples were mechanically stabilized using CDM columns of different area improvement ratio. Further, the ultimate bearing capacity of a rectangular foundation rested on the stabilized peat was calculated in stress-controlled condition. Then, this process was simulated via a FEM-based model using Plaxis 3-D foundation and the numerical modelling results were compared with experimental findings. In the numerical modelling stage, the behaviour of fibrous peat was simulated based on hardening soil (HS) model and Mohr-Coulomb (MC) model, while embedded pile element was utilized for CDM columns. The results indicated that in case of untreated peat HS model could predict the behaviour of fibrous peat better than MC model. The comparison between experimental and numerical investigations showed that the stress distribution between soil (S) and CDM columns (C) were 81%C-19%S (TS-2), 83%C-17%S (TS-3) and 89%C-11%S (TS-4), respectively. This implies that when the area improvement ratio is increased, the share of the CDM columns from final load was increased. Finally, the calculated bearing capacity factors were compared with results on the account of empirical design methods.

• Journal of the Korean Geosynthetics Society
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• v.18 no.2
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• pp.11-21
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• 2019

This paper describes the applicability of FEA(Finite Element Analysis) to the simulation of pile pullout behavior under various soil conditions (relative density and fines content), in order to evaluate reasonably the pullout resistance of pile. That is, the results of previous research (You et al., 2018) were analyzed by FEA under the same conditions. The FEA results showed that axisymmetric analysis using virtual ground was able to evaluate the skin friction of the pile. Also, axisymmetric analysis, which can apply the shear resistance characteristics of the pile-soil interface in various soil conditions, could be used as an analytical method that can simulate a reasonable pile pullout behavior. Therefore, the analytical model proposed in this study was able to simulate appropriately the pullout behavior based on the stress-strain relationship of the pile-soil interface.

• Geomechanics and Engineering
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• v.38 no.3
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• pp.307-317
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• 2024

To get a better understanding of the effect of drying-wetting cycles (DWC) on the mechanical behaviors of silty clay hiving different initial moisture content (IMC), the direct shear tests were performed on sliding band soil taken from a reservoirinduced landslide at the Three Gorges Reservoir area. The results indicated that, as the increasing number of DWC, the shear stress-displacement curves type changed from strain-hardening to strain-softening, and both the soil peak strengths and strength parameters reduced first and then nearly remain unchanged after a certain number of DWC. The effects of DWC on the cohesion were predominated that on the internal friction angle. The IMC of 17% is regarding as the critical moisture content, and the evolution laws of both peak shear strength and strength parameters presented a reversed 'U' type with the rising of the IMC. Based on it, a strength deterioration evolution model incorporating the influence of IMC and DWC was developed to describe the total degradation degree and degradation rate of strength parameters, and the degradation of strength parameters caused by DWC could be counterbalanced to some extent as the soil IMC close to critical moisture content. The microscopic mechanism for the soil strength caused by the IMC and DWC were discussed separately. The research results are of great significance for further understanding the water-weakening mechanicals of the silty clay subjected to the water absorption/desorption.

• Journal of Practical Agriculture & Fisheries Research
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• v.15 no.1
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• pp.95-105
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• 2013

This study has been conducted to investigate the effect of Urea and K₂SO₄ treatment at stone hardening stage and 20 days before harvest on soil chemical properties, mineral nutrient concentration and quality of 'Mibaekdo' fruit peach. K concentration after Urea and K₂SO₄ treatment in soil was increased significantly by Urea 162g+K₂SO₄ 188g/tree(standard amount) treatment at stone hardening stage, K₂SO₄ 1.0% tree-spray, Urea 81g+K₂SO₄ 94g/tree(half amount), Urea 162g+K₂SO₄ 188g/tree and Urea 324g+K₂SO₄ 376g/tree(double amount) soil treatment before harvest 20 days compared to control. T-N, K and Ca concentration in leaf was increased significantly by all treatment. but Na concentration in leaf was increased by Urea 0.5% and K₂SO₄ 1.0% tree-spray treatment before harvest 20 days. T-N concentration in fruit skin was increased significantly by standard amount soil treatment, which decreased by K₂SO₄ 1.0% tree-spray and half amount soil treatment. T-N, K and Ca concentration in fruit flesh(1~10mm depth flesh from peel) were increased markedly by all treatment excepted Urea 0.5% tree-spray. The leaf weight at harvest was increased markedly by Urea 0.5% tree-spray, standard amount and double amount treatment before harvest 20 days. Fruit weight was increased significantly by standard amount compared to all treatment. Red fruit skin(Hunter a value) progress was effective by K₂SO₄ tree-spray, half amount and double amount treatment before harvest 20 days. Fruit SSC was increased significantly by Urea 0.5% and K₂SO₄ tree-spray before harvest 20 days, standard amount treatment at stone hardening stage compared to control.