• Geomechanics and Engineering
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• 제17권2호
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• pp.181-194
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• 2019

Due to the seepage of groundwater, the resisting force of slopes decreases and the sliding force increases, resulting in significantly reduced slope stability. The instability of most natural slopes is closely related to the influence of groundwater. Therefore, it is important to study slope stability under groundwater seepage conditions. Thus, using a simplified seepage model of groundwater combined with the analysis of stresses on the slip surface, the limit equilibrium (LE) analytical solutions for two- and three-dimensional slope stability under groundwater seepage are deduced in this work. Meanwhile, the general nonlinear Mohr-Coulomb (M-C) strength criterion is adopted to describe the shear failure of a slope. By comparing the results with the traditional LE methods on slope examples, the feasibility of the proposed method is verified. In contrast to traditional LE methods, the proposed method is more suitable for analyzing slope stability under complex conditions. In addition, to facilitate the optimization of drainage design in the slope, stability charts are drawn for slopes with different groundwater tables. Furthermore, the study concluded that: (1) when the hydraulic gradient of groundwater is small, the effect on slope stability is also small for a change in the groundwater table; and (2) compared with a slope without a groundwater table, a slope with a groundwater table has a larger failure range under groundwater seepage.

• Journal of Ecology and Environment
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• 제43권2호
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• pp.161-182
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• 2019

Quantifying the amount of carbon pools in forest ecosystems enables to understand about various carbon pools in the forest ecosystem. Therefore, this study was conducted in the Chilimo dry afromontane forest to estimate the amount of carbon stored. The natural forest was stratified into three forest patches based on species composition, diversity, and structure. A total of 50 permanent sample plots of 20 m × 20 m (400 ㎡ ) each were established, laid out on transects of altitudinal gradients with a distance of 100 m between plots. The plots were measured twice in 2012 and 2017. Tree, deadwood, mineral soil, forest floor, and stump data were collected in the main plots, while shrubs, saplings, herbaceous plants, and seedling data were sampled inside subplots. Soil organic carbon (SOC %) was analyzed following Walkely, while Black's procedure and bulk density were estimated following the procedure of Blake (Methods of soil analysis, 1965). Aboveground biomass was calculated using the equation of Chave et al. (Glob Chang Biol_20:3177-3190, 2014). Data analysis was made using RStudio software. To analyze equality of means, we used ANOVA for multiple comparisons among elevation classes at α = 0.05. The aboveground carbon of the natural forest ranged from 148.30 ± 115.02 for high altitude to 100.14 ± 39.93 for middle altitude, was highest at 151.35 ± 108.98 t C ha^-1 for gentle slope, and was lowest at 88.01 ± 49.72 t C ha^-1 for middle slope. The mean stump carbon density 2.33 ± 1.64 t C ha^-1 was the highest for the middle slope, and 1.68 ± 1.21 t C ha^-1 was the lowest for the steep slope range. The highest 1.44 ± 2.21 t C ha^-1 deadwood carbon density was found under the middle slope range, and the lowest 0.21 ± 0.20 t C ha^-1 was found under the lowest slope range. The SOCD up to 1 m depth was highest at 295.96 ± 80.45 t C ha^-1 under the middle altitudinal gradient; however, it was lowest at 206.40 ± 65.59 t C ha^-1 under the lower altitudinal gradient. The mean ecosystem carbon stock density of the sampled plots in natural forests ranged from 221.89 to 819.44 t C ha^-1. There was a temporal variation in carbon pools along environmental and social factors. The highest carbon pool was contributed by SOC. We recommend forest carbon-related awareness creation for local people, and promotion of the local knowledge can be regarded as a possible option for sustainable forest management.

• Smart Structures and Systems
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• 제7권4호
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• pp.263-274
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• 2011

A reliability-based slope stability assessment method considering fluctuations in the monitored matric suction was proposed for real-time identification of slope risk. The assessment model was based on the limit equilibrium model for infinite slope failure. The first-order reliability method (FORM) was adopted to calculate the probability of slope failure, and results of the model were compared with Monte-Carlo Simulation (MCS) results to validate the accuracy and efficiency of the model. The analysis shows that a model based on Advanced First-Order Reliability Method (AFORM) generates results that are in relatively good agreement with those of the MCS, using a relatively small number of function calls. The contribution of random variables to the slope reliability index was also examined using sensitivity analysis. The results of sensitivity analysis indicate that the effective cohesion c' is a significant variable at low values of mean matric suction, whereas matric suction ($u_a-u_w$) is the most influential factor at high mean suction values. Finally, the reliability indices of an unsaturated model soil slope, which was monitored by a wireless matric suction measurement system, were illustrated as 2D images using the suggested probabilistic model.

• Corrosion Science and Technology
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• 제2권4호
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• pp.189-193
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• 2003

The Ru etching using $O_2/C_{12}$ plasmas has been studied by employing the helicon etcher. The changes of Ru etch rate, Ru to $SiO_2$ etch selectivity and Ru electrode etching slope with varied process variables were investigated. The Ru etching slope at the optimized etching condition was measured to be $84^{\circ}$. We reveal that the Ru etching using $O_2/C_{12}$ plasma generates the $RuO_2$ thin film. Possible mechanism of Ru etching is discussed.

• Geomechanics and Engineering
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• 제19권2호
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• pp.179-191
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• 2019

Based on the effective stress principle, a new formula for shear strength of unsaturated soil is derived under the general nonlinear Mohr-Coulomb (M-C) strength criterion to improve the classical strength criterion of unsaturated soil. Meanwhile, the simple irrigation model under steady seepage is adopted to obtain the distribution of the matrix suction or the degree of saturation (DOS) above the groundwater table in the slope. Then, combined with the improved strength criterion of unsaturated soil and the simple irrigation model under steady seepage, the limit equilibrium (LE) solutions for the unsaturated slope stability are established according to the global LE conditions of the entire sliding body with assumption of the stresses on the slip surface. Compared to the classical strength criterion of unsaturated soil, not only the cohesion soil but also the internal friction angle is affected by the matric suction or the DOS in the improved strength criterion. Moreover, the internal friction angle related to the matric suction has the nonlinear characteristics, particularly for a small of the matric suction. Thereafter, the feasibility of the present method is verified by comparison and analysis on some slope examples. Furthermore, stability charts are also drawn to quickly analyze the unsaturated slope stability.

• 환경생물
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• 제25권2호
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• pp.168-177
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• 2007

남한 전 지역을 대상으로 구축된 위도, 고도, 경사, 사면방위, 온량지수, 한랭지수, 연평균기온과 수치 현존식생도에서 추출한 주요 17군락을 MGE프로그램을 이용하여 중첩분석을 통해 17군락의 지형적, 기후적 공간분포 특성과 분포역 및 특성을 결정하는 요인을 밝히고자 하였다. 온량지수(WI)는 수평적으로 위도 $1^{\circ}증가에 $5.27^{\circ}C{\cdot}month$, 수직적으로 표고 100 m 상승함에 따라서 $3.41^{\circ}C{\cdot}month$ 체감하고, WI와 CI사이의 관계는 선형 회귀식 $WI=116.01+0.96{\times}CI,\;R^2=0.996$으로 표현되었다. WI값이 낮은 곳에서 높은 곳으로 분포하는 식물 군락은 Abies nephrolepis, Taxus cuspidata, Abies koreana, Quercus mongolica, Carpinus laxifora, Q. dentata, C. tschonoskii, Q. serrata, Pinus densiflora, Q. aliena, Q. variabiiis, Q. acutissima, P. thunbergii, Q. acuta, Castanopsis cuspidata var. sieboldii, Camellia japonica, Machilus thunbergii community 순으로 나타났다. 신갈나무림은 건조한 남사면이나 남서사면보다 비교적 적습한 서북, 남동사면 등에 분포하며, WI가 $70{\sim}80^{\circ}C{\cdot}month$인 곳에 많이 분포하는 것으로 나타났다. 졸참나무림은 WI $90{\sim}100^{\circ}C{\cdot}month$의 범위를 갖는 대부분의 북서 사면과 서사면에 분포하였다. 굴참나무림과 상수리나무림은 WI $95{\sim}100^{\circ}C{\cdot}month$의 남동 사면에 높은 분포빈도를 보였다. 경사도에 따른 식물군락의 분포를 급경사에서 완경사순으로 1. Abies nephrolepis, Machilus thunbergii, 2. Taxus cuspidata, Abies koreana, Quercus mongolica, Q. dentate, Q. serrata, Q. variabilis, Castanopsis cuspidata var. sieboldii 3. Pinus densiflora, Q. aliena, Q. acutissima, P. thunbergii, Q. acuta 4. Carpinus laxiflora, Camellia japonicas. C. tschonoskii community의 5개 그룹으로 나타났다.

• 한국토양비료학회지
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• 제25권2호
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• pp.111-126
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• 1992

pH와 산화환원(酸化還元) 전위(電位)가 토양(土壤)의 규산흡착(珪酸吸着)에 미치는 영향(影響)을 보기위하여 두개의 필리핀토양과 두개의 한국 토양을 사용하여 실내(室內)에서 실험하였다. 규산의 등온흡착(等溫吸着)은 등온흡착(等溫吸着)의 분류체계(分類體系)에 의하면 약(弱)한 L-type(점근선적(漸近線的) 증가(增加))을 지닌 C-type(직선적(直線的) 증가(增加))에 속(屬)하였다. 규산의 등온흡착(等溫吸着)은 Freundlich와 Tempkin 등온흡착식(等溫吸着式)에 잘 맞았으나 Langmuir 등온흡착식(等溫吸着式)에는 잘 맞지 않았다. Molybdenum-blue 법(法)에 의한 규산 발색시(發色時) 환원(還元) 및 낮은 pH 조건(條件)에서 $Fe^{2+}$ 이온에 기인(起因)된 것으로 보이는 발색장해(發色障害)가 나타났다. Freundlich 식(式)의 절편(切片), Tempkin 식(式)의 기울기, "Silica reactivity"와 C-type slope" 등 4개의 지표(指標)를 규산흡착에 미치는 처리효과 판정(判定)을 위한 지표(指標)로서 검토(檢討)하였다. 이들중 "Silica reactivity"와 C-type slope"는 본(本) 실험에서 제안(提案)된 지표(指標)였다. 4개의 지표(指標)중 "C-type slope"가 가장 좋은 지표(指標)로 판명되었다. C-type 등온흡착(等溫吸着)의 직선회귀(直線回歸)는 Freundlich와 Tempkim식(式)과 거의 동일(同一)한 높은 직선회귀(直線回歸) 상관계수(相關係數)를 보였다. 또한 pH와 log(C-type slope)는 고도(高度)의 직선관계(直線關係)를 보였다. C-type slope를 지표로 이용한 처리효과 분석(分析)결과 pH와 토양종류(土壤種類)는 규산의 토양흡착에 크게 영향을 미치는 반면 산화환원(酸化還元) 전위(電位)의 효과는 없었다. 모든 형태(形態)의 Al과 Fe 및 OM이 규산흡착과 고도(高度)의 상관(相關)을 보였으며 그 중 $Fe_d$가 기여도(寄與度)가 가장 큰 성분(成分)으로 나타났다. 산화(酸化)알루미늄의 분별정량법(分別定量法)이 확립(確立)되어 있지 않은 결과(結果) Al의 기여도(寄與度)는 불확실(不確實)하게 나타나는 것으로 보였다.

• 한국농림기상학회지
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• 제3권4호
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• pp.206-214
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• 2001

본 연구는 경상남도 하동군 하동읍 화심리의 배 과수원에서 주변 지형 특성 및 해발고도별 서리 피해 상습지의 봄철 야간 냉각률, 특정일의 야간기상분포를 구명하고자 수행하였다. 냉각률은 평지에서 3, 4월이 가장 높아 0.7$^{\circ}C$/hr, 9월에 가장 낮아 0.3$^{\circ}C$/hr 정도로 0.4$^{\circ}C$/hr의 차이를 보였다. 일몰 후부터 일출 전까지의 야간기온 냉각률과 유효야간복사의 상관은 r=0.63$^{**}$ 였고, 풍속이 0.5 m/sec 이하에서 야간유효복사와 냉각률은 r=0.90$^{**}$ 으로 상관이 높았으며, 풍속이 강해지면서 냉각률과 상관관계는 낮아졌다. 맑았던 날의 냉각률은 평지(site 1,2,3), 경사면(site 4,5), 산 정상(site 6)에서 각각 시간당 약 1.4$^{\circ}C$, 1.2$^{\circ}C$, 0.6$^{\circ}C$ 하강하여 산 정상으로 갈수록 냉각률이 작아졌다. 맑고 평균풍속이 1.2~2 m/sec이며 산 정상이 경사면이나 평지보다 기온이 낮을 때, 2200~2300경에 경사면(site 4,5)에서의 기온은 떨어지는 것이 아니라 오히려 상승하였다.

• 한국산림과학회지
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• 제19권1호
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• pp.25-31
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• 1973

1) 남서부(南西部) Mojave Desert의 식생관계(植生關係)를 동서남북(東西南北) 사면별(斜面別)로 1971년(年) 12월(月) 10일(日)부터 12일(日) 사이에 분석(分析) 비교(比較)하였다. 2) 조사지중(調査地中). Lycium andersonii가 우점종이고 다음으로 중요치(重要値)가 높은 종(種)들은 Larrea, Ephedra Franseria 등의 순서(順序)이었다. 3) 남사면(南斜面)에서의 Lycium의 중요치(重要値)는 다른 사면식물(斜面植物)보다 높아 약(約) 반(半)을 점유(占有)했다. 4) 식물상(植物相)은 지극(至極)히 단순(單純)하고 밀도(密度)가 낮아 35개(個) $1m^2$ 방형구(方形區) 중(中) 10종(種) 40개본(個本) 이내(以內)였다. 5) 사면별(斜面別) 식생(植生) 차이(差異)는 없었다. 6) 각(各) 사면별(斜面別) 중요치(重要値) 계수(係數)에 의한 군락계수(群落係數)의 비교(比較)에 의하면 87% 이상(以上)으로 거리(距離) 방향(方向)에 관계(關係)없이 이곳은 모두 같은 군총(群叢)에 속(屬)한다. 7) 본(本) 조사지(調査地)에서 공통(共通)으로 나타난 종(種)은 Lycium, Larrea, Ephedra, Franseria, Eriogonum, Yucca, Aster 등 7종(種)이다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 춘계학술대회 논문집
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• pp.451-458
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• 2001

The purpose of this study was to evaluate shear parameters on cutting slope of weathered granite soils by using small dynamic cone penetration test on the very moment of its cutting. The results were : On the relations among N$\_$c/, Li, and CEC, the condition of Li＞6%, CEC＞14(meq/100g) corresponds to that of N$\_$c/ values of 2∼30, and 3＜CEC＜14(meq/100g) to N$\_$c/=30∼50. Comparing the smallest penetration depth from two small dynamic cone penetration tests done at 5m below from the top of the slope on April 15th, October 31t. there was a l0cm difference. So we could find out the degree of weathering on the slope. And dividing the difference by 190 days (the whole testing time), we could know it's being weathered 0.052mm each day. The more N. value increases, the more shear parameters(internal friction angle ; $\phi$, cohesion : c) increase at a standard pressure($\sigma$＞32㎪). So the condition of N$\_$c/=2∼50 corresponds to that of $\phi$=27∼50, c=12∼49㎪. From the above testing results, the N$\_$c/ values more correspond to $\phi$ values than c values. In conclusion, this study suggests that on small dynamic cone penetration test a penetration boundary line of 5 centimeters is decided at around Li=4%, CEC=3(meq/100g) which is classified as a strong weathering soil. It also shows that as Li increases CEC increases as well, while N$\_$c/ decreases.