• Title/Summary/Keyword: 미소환경

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Stiffness Degradation during Deep Excavation in Urban Area (도심지 깊은 굴착에 따른 지반 강성의 변화)

  • Choi, Jongho;Koo, Bonwhee;Kim, Taesik
    • Journal of the Korean GEO-environmental Society
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    • v.16 no.2
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    • pp.27-31
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    • 2015
  • In urban area, many design projects related to geotechnical projects are controlled by serviceability rather than stability requirements. Accordingly, control of ground deformation has become more crucial and many researchers have studied soil stiffness. Recent experimental studies on the stress-strain response of Chicago glacial clays showed that the nonlinearity and anisotropy are the two key factors in evaluating the soil stiffness. In this study, experimental results are applied to analyze the deep excavation site locating in downtown Chicago. The stress paths observed from the observation points located behind and front of the supporting wall yield typical stress paths. Changes in soil stiffness nonlinearity and anisotropy were discussed by comparing experimental and computed stress paths. The stiffness anisotropy were significant even at the first few excavations. The stiffness degradation characteristics are significantly different according to relative location to the support wall even at the same elevation.

Habitat Environment and Feeding Habitat of Iksookimia koreensis and Cobitis lutheri (Pisces: Cobitidae) in the Mangyeong River, Korea (만경강에 서식하는 참종개 Iksookimia koreensis와 점줄종개 Cobitis lutheri의 서식환경과 섭식생태)

  • Ko, Myeong-Hun;Park, Jong-Yeong;Kim, Su-Hwan
    • Korean Journal of Ichthyology
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    • v.21 no.4
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    • pp.253-261
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    • 2009
  • Habitat environment and feeding habitat of Iksookimia koreensis and Cobitis lutheri were investigated in the Mangyeong River, Jeollabuk-do, Korea from 2005 to 2006. They together inhabit the upper and middle stream, but they showed differences in their microhabitat. I. koreensis inhabited the stony zones of relatively rapid waters with a water depth of 30~60 cm, whereas C. lutheri lived in the sandy zones of relatively slow waters with a depth of 30~100 cm. The two species were active during daylight hours from March to October but hibernated in the winter season. During hibernation I. koreensis still lived in the gravel and stone and C. lutheri burrowed in the sand. I. koreensis ingested mainly chironomid and other aquatic insects, whereas C. lutheri fed mainly on Chironomidae, Copepoda and Branchiopoda. The feeding rate of both species was highest in April and September, but they did not feed in the winter.

Simulation on Contaminant Transport in the Aquifer Affected by River Stage (하천 수위의 영향을 받는 대수층에서 오염원의 이동에 관한 모의실험)

  • 김민환
    • Journal of the Korean Society of Groundwater Environment
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    • v.4 no.1
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    • pp.54-59
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    • 1997
  • The river and groundwater are contaminated by pollution source of a waste landfill and others near river. The contaminant transport and response of aquifer parameters are studied in the aquifer affected by variation of river stage. First, the equation for component of variation velocity with river stage is developed by using the analytical solution of groundwater governing equation. The numerical model which considered component of variation velocity is constructed for the transport of mass by advection and dispersion. In order to verify a numerical scheme, the analytical solution is used. The numerical solution is coincided with the analytical one. Aquifer parameters of Nanjido are used as the data for numerical experiment. Second, the range of aquifer parameters is established in order to reponse contaminant transport in aquifer with river stage. The result of numerical experiment shows that the range of the storage coefficient except hydraulic conductivity and effective porosity is relatively sensitive to the contaminant transport. When the storage coefficient is the order of 10$\^$-2/, the response is very sensitive to the variation of river stage.

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Analysis of Load-Settlement Behaviour Characteristics of Granular Compaction Piles from the Model Tests (모형실험에 의한 조립토 다짐말뚝의 하중-침하 관련 거동특성 분석)

  • Kim, Hong-Taek;Kang, Yun
    • Journal of the Korean GEO-environmental Society
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    • v.5 no.4
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    • pp.33-45
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    • 2004
  • In the present study, more systematic laboratory model tests under various conditions are carried out to investigate load-sharing characteristics among the granular pile and adjacent soils and bearing capacity characteristics with different pile lengths. Further to evaluate effects of both a loading area and a spacing of pile installation on the bearing capacity and bearing capacity characteristics of each pile in group, model test results are also analyzed for the purpose of an efficient design of granular compaction piles. From the analysis of the model test results, it is found that the ultimate capacity of granular compaction group piles increases with a decrease in the installation distance among granular piles. It is also found that the dominant failure mode of the granular compaction piles is bulging failure. It is further realized that the length of a granular pile could not significantly affect on the ultimate granular pile capacity.

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Pressure Drop due to Friction in Small Rectangular Channel (미소 사각 채널에서의 마찰 압력 강하)

  • Lim, Tae-Woo;Choi, Jae-Hyuk;Kim, Jun-Hyo;Choi, Yong-Suk
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.18 no.5
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    • pp.461-467
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    • 2012
  • An experimental study was carried out to measure frictional pressure drop in flow boiling to deionized water in a microchannel having a hydraulic diameter of $500{\mu}m$. Tests were performed in the ranges of heat fluxes from 100 to $400kW/m^2$, vapor qualities from 0 to 0.2 and mass fluxes of 200, 400 and $600kg/m^2s$. The frictional pressure drop during flow boiling is predicted by using two models; the homogeneous model that assumes equal phase velocity and the separate flow model that allows a slip velocity between two phases. From the experimental results, it is found that the two phase multiplier decreases with an increase in mass flux. Measured data of pressure drop are compared to a few available correlations proposed for macroscale and mini/microscale. The homogeneous model well predicted frictional pressure drop within MAE of 29.4 % for the test conditions considered in this work.

Measurement of Channel Impedance Characteristics for Indoor Power Line Communications (옥내 전력선 통신 채널 임피던스 특성 측정)

  • Heo Yoon-Seok;Kim Chul;Hong Bong-Hwa;Lee Dae-Young;Jun Kye-Suk
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.42 no.11
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    • pp.79-86
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    • 2005
  • This paper describe a method for measuring line impedance as a function of frequency for an energized powerline in normal operation. A small sinusoidal signal of a powerline communication utility frequency $30khz\~1Mhz$ band is continuously injected into the line, and a implemented impedance analyzer calculates the indoor powerline channel impedance from the measured magnitude and phase of resulting voltage and current. The impedance measurement is executed over a range of frequencies to produce a wideband impedance versus frequency characteristic. Implemented impedance analyzer can analysis powerline communication environments measuring line impedance due to load caused in indoor. And measured analysis information through the database can use to evaluate performance of modem and to decide test environment standard.

An Effect of Layered Earth on Magnetotelluric Responses of Three-Dimensional Bodies (3차원체의 MT응답에 미치는 층상대지의 효과)

  • Kim, Hee Joon;Hong, Chol Hoon
    • Economic and Environmental Geology
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    • v.27 no.5
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    • pp.491-498
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    • 1994
  • The integral equation method is used for magnetotelluric (MT) modeling of a finite inhomogeneity in a two-layered earth. An integral equation relates the incident plane-wave field and the scattering currents in the three-dimensional (3-D) inhomogeneity through the electric tensor Green's function appropriate to a layered earth. This paper describes an effect of overburden and basement on MT responses of 3-D body. The effect of overburden is to reduce the detectability of target, and the reduction of detectability is more apparent for conductive overburden than for resistive one. The effect of basement, on the other hand, may enhance the anomaly due to 3-D body in the upper layer. In case of the resistive basement current perturbations about the body tend to be confined to the more conductive upper layer.

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Classification of Microhabitats based on Habitat Orientation Groups of Benthic Macroinvertebrate Communities (저서성 대형무척추동물의 서식 특성에 따른 미소서식처 유형화)

  • Kim, Jungwoo;Kim, Ah Reum;Kong, Dongsoo
    • Journal of Korean Society on Water Environment
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    • v.33 no.6
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    • pp.728-735
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    • 2017
  • Many restoration projects are underway to revive disturbed streams. In order to achieve successful stream restoration, a variety of microhabitats should be created to promote biological diversity. Research on biological classification of microhabitats is essential for biological diversity. However, research on classification using only physical environmental factors has been carried out. The purpose of this study is to classify and quantify the microhabitat of the stream by using macroinvertebrates systematically. In this study, eight wadeable streams and four non-wadeable streams were surveyed to identify the benthic macroinvertebrates in these various microhabitats. Among the physical environmental factors (current velocity, water depth, substrate), the particle size of the substrate was the most influential factor in the emergence of the Habitat Orientaion Groups. Among the HOGs, clinger and burrower were highly correlated with physical environment factors and showed the opposite tendency. The distribution of clinger and burrower according to the physical environmental factors showed two tendencies based on the current velocity (0.3 m/s) and water depth (0.4 m). In addition, the particle size of the substrate showed three trends (${\leq}-5.0$, -5.0 < mean diameter ${\leq}-2.0$, > -2.0). Based on the abundance tendency of these two HOGs, the microhabitats were classified into nine types, from a eupotamic microhabitat to a lentic microhabitat. Classification of the microhabitats using HOGs can be employed for creating microhabitats to promote biological diversity in future stream restoration plans.

Temporal Distribution of Pico- and Nanoplankton at a Station in Okkye Bay (옥계만 단일정점에서 극미소 및 미소플랑크톤의 시간적 분포)

  • Lee, Won-Je
    • Journal of Environmental Science International
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    • v.16 no.7
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    • pp.855-863
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    • 2007
  • In order to understand the temporal distribution of pico- and nanoplankton and factors controlling its distribution at a station in Okkye Bay of Masan Bay located in the southern part of Korea, this study was conducted on two weeks interval from April 2005 to April 2006, and several abiotic and biotic factors were measured. During the study, picoplankton consisted of picoflagellates, cyanobacteria and heterotrophic bacteria, and nanoplankton consisted of nanoflagellates excluding dinoflagellates. The concentration of chlorophyll-a (chl-a) was a mean of $4.33\;{\mu}g/L$, and the nanoplanktonic ($<20\;{\mu}m$) chl-a size fraction was a mean of 39.5 % and significantly correlated with water temperature. The abundances of cyanobacteria and photosynthetic flagellates (PF) were means of $24.4{\times}10^{3}\;cells/mL\;and\;2.87{\times}10^{3}\;cells/mL$, respectively. The contribution of picoflagellates to the PF abundance varied among the sampling occasions and was a mean of 29 %, but to the PF carbon biomass was 2.6 % only. The PF abundance had significant relationships with water temperature, and silicate and TIN concentrations, suggesting that the PF abundance seemed to be primarily bottom-up regulated. The abundance of heterotrophic bacteria was a mean of $3.18{\times}10^{6}\;cells/mL$ and unlike other ecosystems it did not have relationships with chl-a and heterotrophic flagellates (HF), suggesting that bacterial abundance did not seem to be bottom-up or top-down regulated. HF mostly consisted of cells less than $5{\mu}m$ and its abundance was a mean of $2.71{\times}10^{3}\;cells/mL$. Of the HF abundance, picoflagellates occupied about 31 %, and occupied about 9 % of the HF carbon biomass. HF grazing activity on heterotrophic bacteria was relatively low and removed about 10 % of bacterial abundance, suggesting that HF might not be major consumers of bacteria and there seems to be other consumers in Okkye Bay. These results suggest that Okkye Bay may have a unique microbial ecosystem.

Field Measurement and Numerical Approach for Lateral Deformation of Retaining Wall (흙막이벽에 발생하는 수평변위의 현장계측과 수치해석적 접근)

  • Do, Jongnam;Wrryu, Woongryeal;An, Yihwan;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.2
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    • pp.61-68
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    • 2010
  • Recently, it is a trend of the underground excavation to become larger and deeper for more effective use of available space and with the advent of new excavation technologies. The ground typically has a complex stratigraphy. The excavation can lead to large deformation in the nearby structures and large earth pressure on the wall. This can lead to serious problem in the stability of the wall. For the retaining wall to be safely constructed, it is important that the stratigraphy and engineering properties of the ground be accurately estimated, based on the excavation plan and appropriate excavation method. This study uses the measured field data and numerical results to characterize the characteristics of the lateral deformation of the retaining wall. A touredof six field data were analysed. SUNEX, a numerical program which uses the elasto-plastic model to represent the soil, was used. It was shown that the measured deformations exceeded the proposed values for shallow excavations. Overall, the maximum lateral deformation was within the proposed value and hence, the walls were analyzed as safe.