• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.188-197
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• 2010

This paper presents experimental results of a series of 1-g shaking table model tests performed on end-bearing single piles and pile groups to investigate the effect of particle size on the dynamic behavior of soil-pile systems. Two soil-pile models consisting of a single-pile and a $4{\times}2$-pile group were tested twice; first using Jumoonjin sand, and second using Australian Fine sand, which has a smaller particle size. In the case of single-pile models, the lateral displacement was almost within 1% of pile diameter which corresponds to the elastic range of the pile. The back-calculated p-y curves show that the subgrade reaction of the Jumoonjin-sand-model ground was larger than that of the Australian Fine-sand-model ground at the same displacement. This phenomenon means that the stress-strain behavior of Jumoonjin sand was initially stiffer than that of Australian Fine sand. This difference was also confirmed by resonant column tests and compression triaxial tests. And the single pile p-y backbone curves of the Australian fine sand were constructed and compared with those of the Jumoonjin sand. As a result, the stiffness of the p-y backbone curves of Jumunjin sand was larger than those of Australian fine sand. Therefore, using the same p-y curves regardless of particle size can lead to inaccurate results when evaluating dynamic behavior of soil-pile system. In the case of the group-pile models, the lateral displacement was much larger than the elastic range of pile movement at the same test conditions in the single-pile models. The back-calculated p-y curves in the case of group pile models were very similar in both sands because the stiffness difference between the Jumoonjin-sand-model ground and the Australian Fine-sand-model ground was not significantly large at a large strain level, where both sands showed non-linear behavior. According to a series of single pile and group pile test results, the evaluation group pile effect using the p-multiplier can lead to inaccurate results on dynamic behavior of soil-pile system.

• Geomechanics and Engineering
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• 제5권1호
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• pp.1-15
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• 2013

Pressure transducers are increasingly used within soil mass or at soil-structure interface for appraisal of stresses acting at point of installation. Calibration of pressure transducers provides a unique relationship between applied pressure and voltage or strain sensed by transducer during various loading conditions and is crucial for proper interpretation of results obtained from pressure transducers. In the present study an in-house calibration device is used to calibrate pressure transducers and the study is divided into two parts: 1) demonstration of developed calibration device for fluid and in-soil calibration of pressure transducers; 2) effect of soil layer thickness on the earth pressure cell (EPC) output. Results obtained from the present study revealed successful performance of the developed calibration device, and significant effect of sand layer thickness on the calibration results. The optimum sand layer thickness is obtained as 1.5 times the diameter of EPC.

• 한국토양비료학회지
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• 제49권6호
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• pp.705-711
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• 2016

Crimson clover, a legume crop, is a landscape crop and green manure crop that can be sowing in spring and autumn. Its red flower blooms in May, and serves various roles such as landscape composition, weeds suppressing, prevention of soil loss and nutrient on sloping land and supplying nitrogen and organic matter in soil. Thus, in order to utilize this crop in agriculture land, we evaluated the growth characteristics of crimson clover cultivated in four different soil textures; sand, sandy loam, loam, and clay loam. The nitrogen content of crimson clover was $15.8g\;kg^{-1}$ and C/N ratio was 20.3. Its plant height was 42.5 cm in sandy loam and 49.5 cm in loamy, respectively, approximately 20 cm longer than the sand and clay loam. The crimson clover in sandy loam and loam bloomed about seven days earlier than those in sand and clay loam. Regarding number of flower per hill and flower length, there were no difference among the soil textures. Dry weight of crimson clover for sandy loam and loam was $2.5Mg\;ha^{-1}$ and $2.3Mg\;ha^{-1}$, respectively, $0.8{\sim}1.1Mg\;ha^{-1}$ higher than that of sand and sandy loam. Plant height and dry weight of crimson clover increased with delaying harvest time. Nitrogen contribution in loam and clay loam was $51.3kg\;ha^{-1}$ and $53.5kg\;ha^{-1}$, respectively. Therefore, in terms of flowering properties and dry weight, the proper soil texture for the growth and development of crimson clover was sandy loam and loam.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.743-750
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• 2002

Unsaturated soil has a possibility to induce a negative pore water pressure. Until now, saturated soil is mainly focused on the research of soil mechanics. Recently, soil mechanics is researched on two major parts such as saturated and unsaturated soil mechanics. Negative pore water pressure has a non-linear relationship with the water content changes. Soil-water characteristic curves of soil in Korea are not determined. There is no proper characteristic value such as air-entry value and residual water content. In this study, the characteristic curves of reclaimed soil, sand, and weathered granite soil were determined by laboratory tests. Air-entry value and residual water content were determined by fitting methods. Soil-water characteristic curves were estimated based on the particle-size distribution and compared with the laboratory test results. The results of soil-water characteristic curves estimation indicated that Fredlund and Wilson's model is excellent for sand and weathered granite soil. Arya and Paris's model is excellent for reclaimed soil.

• Structural Engineering and Mechanics
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• 제64권6권
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• pp.703-721
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• 2017

The experimental study of the behavior of dry medium and loose sandy soil under the action of a single impulsive load is carried out. Different falling masses from different heights were conducted using the falling weight deflectometer (FWD) to provide the single pulse energy. The responses of soils were evaluated at different locations (vertically below the impact plate and horizontally away from it). These responses include; displacements, velocities, and accelerations that are developed due to the impact acting at top and different depth ratios within the soil using the falling weight deflectometer (FWD) and accelerometers (ARH-500A Waterproof, and Low capacity Acceleration Transducer) that are embedded in the soil and then recorded using the multi-recorder TMR-200. The behavior of medium and loose sandy soil was evaluated with different parameters, these are; footing embedment, depth ratios (D/B), diameter of the impact plate (B), and the applied energy. It was found that increasing footing embedment depth results in: amplitude of the force-time history increases by about 10-30%. due to increase in the degree of confinement with the increasing in the embedment, the displacement response of the soil will decrease by about 25-35% for loose sand, 35-40% for medium sand due to increase in the overburden pressure when the embedment depth increased. For surface foundation, the foundation is free to oscillate in vertical, horizontal and rocking modes. But, when embedding a footing, the surrounding soil restricts oscillation due to confinement which leads to increasing the natural frequency, moreover, soil density increases with depth because of compaction, that is, tendency to behave as a solid medium.

• 한국환경복원기술학회지
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• 제8권6호
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• pp.13-20
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• 2005

본 연구는 자생지환경에서 배합토에 따른 더부살이고사리의 생육을 살펴봄으로써 적정한 생육환경을 구명함은 물론, 실내조경용 소재로 활용성을 높이기 위해 수행하였으며 그 결과는 다음과 같다. 1. 더부살이고사리는 비침상조건보다 침상조건에서 생육이 좋았으며 배합토에 있어서는 밭흙 : 마사토 : 부엽토처리구가 마사토 : 부엽토처리구나 부엽토 단용처리구보다 초장, 소엽장, 소엽폭, 엽병, 관상가치가 높았다. 2. 엽체생중과 엽건조중은 전반적으로 침상조건보다는 비침상조건에서 높았으며 침상조건에서의 엽생체중과 엽건조중은 밭흙 : 마사토 : 부엽토처리구가 다른 배합토에 비해 높았다. 3. 포자엽수는 비침상보다 침상조건에서는 증가하는 경향을 나타내었으며 마사토 : 부엽토처리구가 밭흙 : 마사토 : 부엽토처리구나 부엽토 단용처리구보다 많았다. 4. 생리활성의 경우 기공전도도, $CO_2$이용효율은 밭흙 : 마사토 : 부엽토처리구> 마사토 : 부엽토처리구> 부엽토 단용처리구 순으로 되었으나 광합성률, $CO_2$흡수율, 수분이용효율은 부엽토 단용이 다른 두가지 배합토보다 높았다.

• The Korean Journal of Ecology
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• 제20권2호
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• pp.133-143
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• 1997

From 1984 to 1989 reclaimed coastal lands in Choongnam Province of the western coast of Korea were studied for soil texture at three sites(Daeho, Hyundai A and Hyundai B) and for desalination one site(Hyundai B). The soil textures of varied sites in Hyundai A were horizontally similar and composed of 39-40% clay, 40-49% silt and 8-14% sand. But those in Da돼 and Hyundai B differed horizontally in the same area and vertically at the same site. Soil texures of Da돼 were composed of 15-17% clay, 30-45% silt and 40-55% sand and those of Hyundai B were composed of 22-45% clay, 26-49% silt and 17-31% sand. The measured electrical conductivity(EC), which represents whole salt content of the reclaimed soil, decreased year by year. The vertical distribution of the EC changed temporally and spatially in the upper zone above a 50 cm depth but not in The lower zone below a 50 cm depth. The EC valus of the soil were inversely proportional to the magnitued of annual precipitation, evaporation and the numbers of rainy days with r equalling -0.97. But the annual decrease of the EC was directly proportional to climatic factors with r=0.7. Salt in the reclaimed land was leached out by the percolative action of surplus rain water, or moved up by evaporation and carried away by running rain water. The running out of the salt on the soil surface was most efficiently carried out over 10 mm precipitation per day.

• Geomechanics and Engineering
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• 제33권5호
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• pp.439-451
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• 2023

The construction of shield tunnelling in urban sites is facing serious risks from complex and changeable underground conditions. Construction problems in the sand-clay mixed ground have been more reported in recent decades for its poor control of soil loss in tunnel face, ground settlement and supporting pressure. Since the limitations of observation methods, the conventional physical modelling experiments normally simplify the tunnelling to a plane strain situation whose results are not reliable in mixed ground cases which exhibit more complicated responses. We propose a new method for the study of the mixed ground tunnel through which mixed lays are simulated with transparent soil surrogates exhibiting different mechanical properties. An experimental framework for the transparent soil modelling of the mixed ground tunnel was established incorporated with the self-developed digital image correlation system (PhotoInfor). To understand better the response of face stability, ground deformation, settlement and supporting phenomenon to tunnelling excavation in the sand-clay mixed ground, a series of case studies were carried out comparing the results from cases subjected to different buried depths and mixed phenomenon. The results indicate that the deformation mode, settlement and supporting phenomenon vary with the mixed phenomenon and buried depth. Moreover, a stratigraphic effect exists that the ground movement around mixed face reveals a notable difference.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.649-656
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• 2000

Consolidation of the ground surrounding the sand piles is delayed by well resistance and smear effect. This study is executed to understand the factors that affect the characteristics of consolidation. This was accomplished by utilizing the estimated and measured values of the soil properties through the monitoring of the ground surrounding the sand piles. When it is assumed that the horizontal coefficient is equal to the vertical coefficient of consolidation, the estimated values is exceedingly similar to the measured values. The properties of the initially disturbed soil by the sand pile installation seemed to improve through the process of consolidation with the passage of time. From the results of the analysis of the settlement measurement, the measured values occurred about 60～90% of the predicted values. Considering the initial radical compression deformation, according to the theory of cavity expansion, the difference between the two appears to be in good agreement. In this study, to understand the behavioral characteristics of the ground surrounding the sand piles requires estimation through considering the initial radial compression as well as smear effect of the soil disturbance and well resistance.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1032-1037
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• 2006

This thesis studied effects of the excavation around railroads on the deformation of the lateral ground and neighboring railroads. The conclusions of the study are as follows. 1. When the depth of excavationis 10m, the influential area should be 35m for soft clay, 20m for normal clay, 15m for hard clay, 15m for loose sand, 12m for slightly dense sand, and 8m for dense sand. 2. When the influential area is 10m, the allowable excavation depth should be 2.5m for soft clay, 4.8m for normal clay, 7.5m for hard clay, 7.2m for loose sand, 8.8m for slightly dense sand, and 10m for dense sand. 3. When the influential area is 20m, the allowable excavation depth should be 4.5m for soft clay, and up to 10m for the other five kinds of soil. 4. When the influential area is 30m, the allowable excavation depth should be 7.5m for soft clay, and up to 10m for the other five kinds of soil. 5. When the influential area is 35m, the allowable excavation depth should be up to 10m for all kinds of soil.