• 한국농공학회논문집
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• 제47권6호
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• pp.47-57
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• 2005

Stress distribution in soils is the very important element to design and to solve the problems of settlement, safety of foundations and trafficability of constructing vehicle in civil engineering. This research presents the comparative estimation of the actual and theoretical measurement on the underground stress of outer layer for each soil after the observation of each top soil layer fur its vertical and horizontal stresses in (1) homogeneous sand ground (2) weak stratum with the sand soil (3) weak stratum with gravel of the soil model, and it also investigates the effect of subsidence of ground by the repeated load. The underground stresses fumed out to be different in the value of theoretical and actual measurement after the trial examination of model. This study has the purpose of suggesting the better construction method of running equipment on weak stratum by comparing the estimated value of trial experiment and theory on underground stress of the weak ground surface area and of raising up the necessity of the continuous research hereafter.

• Journal of Ecology and Environment
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• 제42권4호
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• pp.155-162
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• 2018

Background: In ecosystem carbon cycle studies, distinguishing between $CO_2$ emitted by roots and by microbes remains very difficult because it is mixed before being released into the atmosphere. Currently, no method for quantifying root and microbial respiration is effective. Therefore, this study investigated the relationship between soil respiration and underground root biomass at varying distances from the tree and tested possibilities for measuring root and microbial respiration. Methods: Soil respiration was measured by the closed chamber method, in which acrylic collars were placed at regular intervals from the tree base. Measurements were made irregularly during one season, including high temperatures in summer and low temperatures in autumn; the soil's temperature and moisture content were also collected. After measurements, roots of each plot were collected, and their dry matter biomass measured to analyze relationships between root biomass and soil respiration. Results: Apart from root biomass, which affects soil's temperature and moisture, no other factors affecting soil respiration showed significant differences between measuring points. At each point, soil respiration showed clear seasonal variations and high exponential correlation with increasing soil temperatures. The root biomass decreased exponentially with increasing distance from the tree. The rate of soil respiration was also highly correlated exponentially with root biomass. Based on these results, the average rate of root respiration in the soil was estimated to be 34.4% (26.6~43.1%). Conclusions: In this study, attempts were made to differentiate the root respiration rate by analyzing the distribution of root biomass and resulting changes in soil respiration. As distance from the tree increased, root biomass and soil respiration values were shown to strongly decrease exponentially. Root biomass increased logarithmically with increases in soil respiration. In addition, soil respiration and underground root biomass were logarithmically related; the calculated root-breathing rate was around 44%. This study method is applicable for determining root and microbial respiration in forest ecosystem carbon cycle research. However, more data should be collected on the distribution of root biomass and the correlated soil respiration.

• Journal of Plant Biology
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• 제14권1호
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• pp.5-13
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• 1971

Accumulation of soil organic matter and its vertical distribution at different latitudes in peninsular Korea were studied in the soil of four different forest types viz. Pinus densiflora forest, Castanea forest, Quercus acutissima forest and Carpinus laxiflora forest. Among them, accumulation of soil organic matter in Cheju sites, with a mean annual temperature of 15$^{\circ}C$, was maximum with increasing latitude, soil organic matter concentration decreased. Considering the relationship between concentration of soil organic matter and some climatic conditiions, it seems that concentrations of soil organic matter is a function of annual temperature, especially warmth index or cold index.

• Journal of Ecology and Environment
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• 제30권1호
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• pp.17-21
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• 2007

The organic carbon (OC) distribution of Pinus densiflora forest in Songgye valley at Mt. Worak National Park were studied as a part of the National Long-Term Ecological Research in Korea. In order to investigate the OC distribution, OC in plant biomass, litterfall, litter layer on forest floor, and soil were estimated. The density of P. densiflora forest was 1,300 trees/ha, average DBH was $15.2{\pm}6.17\;cm$ and average tree height was $10.7{\pm}2.56\;m$. The shrub layer was dominated by shrubby Quercus variabilis, Fraxinus sieboldiana and lndigofera kirilowii with low frequency, and herb layer was dominated by Pteridium aquilinum and Miscanthus sinensis. Total amount of OC stored in this pine forest was 142.78 ton C/ha. Organic carbon stored in soil and plant biomass accounted for 59.2% and 37.8%, respectively. Amount of OC distributed in trees, shrubs, herbs and litter layer in this pine forest was 51.79, 2.03, 0.12 and 4.29 ton C/ha, respectively. Amount of OC returned to forest floor via litterfall was $1.50\;ton\;C\;ha^{-1}\;yr^{-1}$. Soil organic carbon (SOC) decreased along the soil depth. Total amount of SOC within 50cm soil depth was $84.55\;ton\;C\;ha^{-1}\;50\;cm-depth^{-1}$.

• 공업화학
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• 제25권1호
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• pp.27-33
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• 2014

석유누출 사고로 인해 토양과 지하수 오염이 점차 증가되면서, 토양환경에 대한 중요성이 늘고 있다. 토양오염은 다른 환경오염에 비해 많은 정화비용과 긴 정화기간이 요구된다. 이런 이유로 토양오염이 발생되면, 어떤 오염물질에 의해 토양이 오염되었으며, 토양정화의 책임이 있는 오염자가 누구인지 법적 분쟁이 많이 발생되고 있다. 본 연구에서는 토양오염을 발생시킬 수 있는 항공유에 대한 물성 분석과 함께 항공유 내의 특정 첨가제를 분석함으로써 등유와 항공유의 구분법을 찾아내었다. 특히 발색제에 의해 등유 내 화학적 식별제만 발색되었으며, GC-MS 분석결과 항공유에서만 산화방지제와 금속불활성제가 분석되었다. 이는 추후 항공유에 의한 토양오염 야기 시, 어떤 석유제품에 의한 오염인지 쉽게 판단이 가능할 것이다.

• 한국지반공학회논문집
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• 제22권10호
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• pp.47-54
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• 2006

H pile은 원형말뚝에 비해 항타에 의해 쉽게 관입이 되며, 높은 주면마찰력과 폐색효과를 나타내는 특징을 가지고 있다. 본 연구에서는 실내시험을 통한 화강풍화토 지반에 관입된 H형강 무리말뚝의 주면마찰력 분포특성을 관찰하는데 목적이 있다. 말뚝의 배열$(1{\times}2,\;1{\times}3,\;2{\times}2,\;2{\times}3,\;3{\times}3)$, 말뚝설치간격(2D, 4D, 6D)과 지반밀도(40%, 80%)에 따른 재하시험을 실시하였다. 실험결과 전체 재하중에 대한 주면마찰력의 분포비율은 $3{\times}3$ 무리말뚝의 경우 말뚝간격비가 증가할수록 조밀한 지반의 경우 $48{\sim}39%$, 느슨한 지반의 경우에는 $32{\sim}27%$로 각각 감소하였다 그리고 말뚝침하량에 따른 주면마찰력 분포비율은 느슨한 지반조건에서 $2{\times}2$무리말뚝의 경우 $58{\sim}33.2%$, $3{\times}3$무리말뚝의 경우 $65{\sim}38%$로 각각 감소되었다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.20-23
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• 2000

The use of electrokinetic injection and transport for the distribution of an NAPLs-degrading microorganism in a sandy soil bed was studied. After the injection of the cell into cathode side of bed, an electric current was applied. The transport of cell though the sandy soil was achieved by electokinetics, mainly by electrophoresis, The pH control in electrode chamber plays un important role to achieve desirable cell transport because H$^{+}$ generated at anode is toxic or inhibits the transport of cells. Electokinetic distribution rate of bacterial cells changed depending on the applied electric current and pH. The degradation of diesel by electrokinetically transport cells were monitored.d.

• 한국농공학회논문집
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• 제60권2호
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• pp.95-101
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• 2018

The objective of this study is to evaluate the liquefaction cyclic shear stress ratio considering the soil uncertainty. In this study, the probabilistic ground response analysis and the cyclic shear stress ratio analysis for the liquefaction potential evaluation are performed considering the soil variability. The statistical properties of input ground parameters were analyzed to investigate the parameters affecting the seismic response analysis. The Probabilistic analysis was carried out by Monte Carlo Simulation method. The ground response analysis was performed considering the soil variability and the probability distribution characteristics of the ground acceleration. The probability distribution of the peak ground acceleration by seismic characteristics was presented. The differences of liquefaction shear stress ratio results according to soil variability were compared and analyzed. The maximum acceleration of the ground by the deterministic method was analyzed to be overestimation of the ground amplification phenomenon. Also, the shear stress ratio was overestimated.

• 한국농공학회논문집
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• 제51권6호
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• pp.83-90
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• 2009

This study was carried out to evaluate the vertical stress properties in sandy soil according to changes of loading type in soil bin compacted three layers. The following conclusions and comparisons have been made based on careful analysis from theoretical and experimental methods. : When sandy soil subjected to cycle-loading, compression of foundation and diffusion of vertical stress increment(${\Delta}{\sigma}_2$) were influenced by magnitude of loading plate. When sandy soil subjected to reloading after removing of pre-loading, the distribution of ${\Delta}{\sigma}_2$ depth at one time of loading plate width was different from its distribution at more deep point cause of load hysteresis, so in case of design of structure, the effect of ${\Delta}{\sigma}_2$ as depth must be considered. The increment of vertical stress will be different as loading condition and foundation depth, the loading condition must be considered in case of structure design.

• Geomechanics and Engineering
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• 제23권5호
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• pp.431-439
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• 2020

Soil-water retention curve (SWRC) contains key information for the application of unsaturated soil mechanics principles to engineering practice. The SWRC variables are commonly used to describe the hydro-mechanics of soils. Generally, these parameters are determined using the graphical method which can be time consuming. The SWRC is highly dependent on the pore size distribution (PSD). Theoretically, the PSD obtained by mercury intrusion porosimetry test can be used to determine some SWRC variables. Moreover, the relationship between SWRC and shrinkage curve has been investigated. A new method to determine total SWRC variables directly without curve-fitting procedure is proposed. Substituting the variables into linear SWRC equations construct SWRC. A good agreement was obtained between predicted and measured SWRCs, indicating the validity of the proposed method for unimodal SWRC.