• Ocean Systems Engineering
• /
• 제6권2호
• /
• pp.161-189
• /
• 2016

This paper provides a practical stochastic method by which the maximum equilibrium scour depth around a vertical pile exposed to random waves plus a current on mild slopes can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes including the effect of breaking waves, and using the empirical formulas for the scour depth on the horizontal seabed by Sumer and Fredsøe (2002). The present approach is valid for wave-dominant flow conditions. Results for random waves alone and random wave plus currents have been presented and discussed by varying the seabed slope and water depth. An approximate method is also proposed, and comparisons are made with the present stochastic method. For random waves alone it appears that the approximate method can replace the stochastic method, whereas the stochastic method is required for random waves plus currents. Tentative approaches to related random wave-induced scour cases on mild slopes are also suggested.

• Geomechanics and Engineering
• /
• 제6권1호
• /
• pp.1-15
• /
• 2014

In this study, artificial neural network (ANN) and multiple regression (MR) models were developed to predict the critical factor of safety ($F_s$) of the homogeneous finite slopes subjected to earthquake forces. To achieve this, the values of $F_s$ in 5184 nos. of homogeneous finite slopes having different slope, soil and earthquake parameters were calculated by using the Simplified Bishop method and the minimum (critical) $F_s$ for each of the case was determined and used in the development of the ANN and MR models. The results obtained from both the models were compared with those obtained from the calculations. It is found that the ANN model exhibits more reliable predictions than the MR model. Moreover, several performance indices such as the determination coefficient, variance account for, mean absolute error, root mean square error, and the scaled percent error were computed. Also, the receiver operating curves were drawn, and the areas under the curves (AUC) were calculated to assess the prediction capacity of the ANN and MR models developed. The performance level attained in the ANN model shows that the ANN model developed can be used for predicting the critical $F_s$ of the homogeneous finite slopes subjected to earthquake forces.

• 한국지반공학회논문집
• /
• 제18권2호
• /
• pp.123-136
• /
• 2002

강우시 발생하는 여러 사면의 얕은 파괴는 지표로 침투하는 강우에 의한 포화깊이 증가에 의해 발생한다. 본 연구에서는 불포화사면 해석을 위하여 국내의 전형적인 표토층을 구성하는 화강풍화토를 3가지(SW, SP, SM)로 분류하여 함수특성곡선을 각각 구하고 그에 따른 함수특성곡선의 방정식을 추정하였으며, 기존에 사용되고 있는 Green & Ampt의 포화깊이 추정식과 수치해석 결과를 비교.분석함으로써 추정식의 사용범위에 대한 제한성을 파악하였다. 또한, 강우에 의한 사면의 포화깊이가 사면의 안정성에 미치는 영향을 파악하고 화강풍화토의 함수특성곡선을 이용하여 불포화사면의 강도정수를 추정하여 계산된 불포화지반의 해석이 기존의 포화사면의 해석에 비하여 보다 정확한 결과임을 알 수 있었다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.171-178
• /
• 2005

It is unavoidable to be formed slopes under special circumstance of Korea where 70% of the whole area are composed of mountains when civil engineering projects such as roads, site developments are increased with industrial development and horizontal expansions of urban area. Moreover, stability of the slopes become one of quite important issues under special meteorological characteristics that over two-thirds of annual average rainfall are concentrated in summer season and the localized torrential downpour are getting more frequent recently. Resulting in these circumstances, partial slope failures by debris flow of the high water content soils are occurred frequently in cutting soil slopes. In this case of debris flow slope failure, slope declination method are selected for their stable recovery because it is impossible to recover entirely by existing recovery methods. Seeding or special grass planting methods are followed separately without exception. The method by which entire recover with bigger stability ratio would be possible and grass planting work would be done simultaneously is developed. In this study, the results of the tests including a real construction history in a failed slope using developed method are described

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.199-206
• /
• 2005

Engineers have performed slope stability analyses, including Limit Equilibrium Analysis, Finite Difference Analysis and Finite Element Analysis. Each analysis results in different Factor of Safety(FS) for slopes. The comparison of FS results from these stability analyses has been carried out for various conditions, such as geometry of slopes, dry and fully saturated soils, nail and anchor reinforcements. Standard deviations of FS calculated from various slope analyses are 0.03 to 0.04 and 0.22 to 0.48 for the slopes without and with nail or anchor reinforcement, respectively. Construction of tiered concrete retaining wall in addition to nail or anchor reinforcement increases FS of 12% to 29% for fully saturated soils.

• 한국환경과학회지
• /
• 제22권10호
• /
• pp.1345-1351
• /
• 2013

Leaf characteristics of two representative deciduous-tree species in Korean peninsula were compared to assess directional ridge effect on leaf traits of both species. Leaf mass per unit area (LMA) of Rhododendron schilippenbachii in south-facing ridge slope was significantly higher than that in north-facing ridge slope, while Quercus mongolica did not change LMA. Leaf mass of Q. mongolica was increased depending on leaf size irrespective of slope. However, leaf mass of R. schilippenbachii changed differently in responding to expansion of leaf area between both slopes resulting from retardation of leaf expansion in south-facing slope. R. schilippenbachii showed higher leaf nitrogen concentration per unit area (LNCA) in south-facing slope than that in north-facing slope, while Q. mongolica indicated no difference in LNCA between southand north-facing slopes. However, both species revealed no significant difference in leaf nitrogen concentration per unit mass (LNCM) between south- and north-facing slopes. LNCA of Q. mongolica was about two times higher than that of R. schilippenbachii. These results indicate that there is a difference in leaf characteristics including leaf thickness and nitrogen allocation between Q. mongolica and R. schilippenbachii, suggesting the difference of plasticity.

• 대한토목학회논문집
• /
• 제4권3호
• /
• pp.11-18
• /
• 1984

사면의 안정 해석방법은 사면의 제반 조건 및 파괴면의 형태에 따라 유한사면법과 무한 사면법 등으로 나눌수 있는데 무한사면법은 그 해석 방법이 단순 명료하여 사용이 간편한 반면에, 단영향을 무시하고 경사면에 평행한 파괴면을 가정하는 등 대략적인 면이 있어서 그 적용범위에 한계성을 내포하고 있다. 본 논문에서는 무한사면법을 적용하여 공학적으로 허용할 수 있는 범위내의 오차를 주는 사면을 정의하기 위하여 가상사면을 다양하게 설정하고 각 사면에 대한 유한 사면법과 무한 사면법의 안정해석 결과를 안전률을 이용하여 비교 분석하였다. 그 결과로 무한사면법은 무한사면파괴가 예상되는 한계높이에 대한 사면높이의 비가 대략 9보다 같거나 클때 적용 가능하다고 판단되었다.

• 환경영향평가
• /
• 제18권1호
• /
• pp.51-57
• /
• 2009

Corylopsis coreana Uyeki is endemic species in the Korean peninsula and is designated a Category Endangered Plant Species by the Wildlife Protection Act of South Korea. We developed the plan and cooperative model within the local community for the species conservation. In order to carry out this plan we first investigated the ecological characteristics of the species. The species shows patterns of discontinuous distribution and is coupled with the unusual feature of only growing on northern exposed slopes. Although Corylopsis coreana is cut the stem every year, many new sprouts are still grown from the root. Natural germination of the seed occurs only on north-facing slopes, but not on south-facing slopes at spring. That is, the species is highly influenced by soil moisture until the seedling stage has been reached. This factor limits the distribution of the species. When saplings are planted on south-facing slopes, they grow well. The information we gathered greatly helped with efforts to draw up conservation plans. In addition, when the information was shared with the local community, builders and residents showed great interest and displayed a will to help with conservation efforts. Therefore, a cooperative model within the local community was drawn up for the conservation of the species. Accordingly this model could be applied at mitigation measure at environment impact assessment.

• 한국환경복원기술학회지
• /
• 제8권1호
• /
• pp.10-16
• /
• 2005

This experiment was conducted to study on application of several Korean native plants by seed spray methods for cut slope revegetation, and possibility of replacement almost imported tall fescue seeds by native herbaceous plants. So, we investigated growth and covering rate after sowing native plants seeds at the artificial slope plots in Suwon and the rock exposed cut-slopes in Wonju city. Emergence rate after seed spray at artificial slopes were higher Elsholtzia splendens and Dianthus superbus var. longicalycinus, showing the highest in E. splendens. Also, E. splendens, D. superbus var. longicalycinus, and Agrostemma coronaria were possible to use for seed spray at the rock exposed cut-slopes. The plots of mixed native plants show more seasonal scenery than that of tall fescue. Soil surface run-off by Typhoon was less in plot sown native plants than those of lawn grass, resulting fresh weight of roots was heavier. Thus, we found that the mixed seed spray of several native herbaceous plants, E. splendens, D. superbus var. longicalycinus, and Agrostemma coronaria, were well covered the slopes as tall fescue.

• Journal of Electrical Engineering and Technology
• /
• 제4권1호
• /
• pp.143-148
• /
• 2009

About 70% of Korea consists of mountainous areas, and during the construction of many roads and railroads, cut slopes are inevitably formed. The rainy season, frost heaving in winter, and thawing in spring can all cause rockfalls and landslides. The failure of these slopes is increasing every year, causing damage to vehicles, personal injury and even death. To protect people and property from such damage, a real-time monitoring system is needed to detect the early stages of slope failures. The GMG placed TRS sensor units in the slopes to monitor them in real-time. But due to its reliance on data lines and power lines, the system is vulnerable to lightning damage. The whole system can be damaged by a single lighting strike. Consequently, for the purposes of this paper we propose the use of the Ubiquitous Sensor Network (USN) which follows the IEEE 802.1.4. By using the USN system we can minimize lightning damage and can monitor the movement of the slopes consistently.