• Title/Summary/Keyword: Embankment structure

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An Evaluation on Restoration Effect in the Restored Yangjae Stream and the Improvement Plan Based on the Result (복원된 양재천에서 복원 효과 평가 및 평가 결과에 기초한 개선방안)

  • Kim, A Reum;Kim, Dong Uk;Lim, Bong Soon;Seol, Jae Won;Lee, Chang Seok
    • Korean Journal of Ecology and Environment
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    • v.53 no.4
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    • pp.390-407
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    • 2020
  • This study was carried out to evaluate the restoration effect in the restored Yangjae stream and to draw up an adaptive management plan based on the results. As the result of evaluation on the restoration effect, the restored Yangjae stream was evaluated with low naturalness in both terms of the morphology of the stream and the composition and spatial distribution of vegetation. The diverse functional groups were introduced in the vegetation restoration, but the flooding regime, which is significant in the spatial distribution of riparian vegetation, were not correctly reflected. Exotic species or species that were not ecologically suitable for the location were introduced on the embankment and thus a measure to improve those problems is required. As the ecological principle was not reflected in the restoration plan, the stream was constructed as the double terrace structure. Therefore, the width of the waterway was narrowed further, and the waterfront was not designed to accommodate changes from flooding disturbance, making the micro-topography of the stream simpler and the naturalness lower. The adaptive management plan was prepared to improve those problems, and a plan for creating an ecological network was recommended to enhance the restoration effect.

Study on the transient flow induced by the windbreak transition regions in a railway subject to crosswinds

  • Zheng-Wei, Chen;Syeda Anam, Hashmi;Tang-Hong, Liu;Wen-Hui, Li;Zhuang, Sun;Dong-Run, Liu;Hassan, Hemida;Hong-Kang, Liu
    • Wind and Structures
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    • v.35 no.5
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    • pp.309-322
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    • 2022
  • Due to the complex terrain around high-speed railways, the windbreaks were established along different landforms, resulting in irregular windbreak transition regions between different subgrade infrastructures (flat ground, cutting, embankment, etc). In this paper, the effect of a windbreak transition on the wind flow around railways subjected to crosswinds was studied. Wind tunnel testing was conducted to study the wind speed change around a windbreak transition on flat ground with a uniform wind speed inflow, and the collected data were used to validate a numerical simulation based on a detached eddy simulation method. The validated numerical method was then used to investigate the effect of the windbreak transition from the flat ground to cutting (the "cutting" is a railway subgrade type formed by digging down from the original ground) for three different wind incidence angles of 90°, 75°, and 105°. The deterioration mechanism of the flow fields and the reasons behind the occurrence of the peak wind velocities were explained in detail. The results showed that for the windbreak transition on flat ground, the impact was small. For the transition from the flat ground to the cutting, the influence was relatively large. The significant increase in the wind speeds was due to the right-angle structure of the windbreak transition, which resulted in sudden changes of the wind velocity as well as the direction. In addition, the height mismatch in the transition region worsened the protective effect of a typical windbreak.

The Structual Restoration on Gyeongju-Style Piled Stone-Type Wooden Chamber Tombs (경주식 적석목곽묘의 구조복원 재고)

  • Gweon, Yong Dae
    • Korean Journal of Heritage: History & Science
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    • v.42 no.3
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    • pp.66-87
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    • 2009
  • The definition of the structure of wooden chamber tomb(piled stone-type) is as follows. It is a tomb with wooden chamber, and stones were piled on top of the wooden chamber, and then a wooden structure was placed on top of the piled stones, and more stones were piled on top of the wooden structure, and sealed with clay. Of course this definition can vary according to periods, the buried, etc. Gyeongju-style piled stone type wooden chamber tombs have some distinguished characteristics compared to general definition of piled stone type wooden chamber tombs. Outside the wooden chamber, either stone embankments or filled-in stones were layed out, and pilet-in stones are positioned right above the wooden chamber, and almost every class used this type, and finally, it is exclusively found in Gyeongju area. First generations of this Gyeongju-style piled stone type wooden chamber tombs appeared in first half of 5th century. These tombs inherited characteristics like ground plan, wooden chamber, double chamber(inner chamber and outer chamber), piled stones, burial of the living with the dead, piled stones, from precedent wooden chamber tombs. However these tombs have explicit new characteristics which are not found in the precedent wooden chamber tombs such as stone embankments, wooden pillars, piled stones(above ground level), soil tumuluses. stone embankments and wooden pillars are exclusively found on great piled stone type above-ground level wooden chamber tombs such as the Hwangnamdaechong(皇南大塚). Stone embankments, wooden pillars, piled stones(above ground level) are all elements of building process of soil tumuluses. stone embankments support outer wall of above-ground level wooden chambers and disperse the weight of tumuluses. Wooden pillars functioned as auxiliary supports with wooden structures to prevent the collapse of stone embankments. Piled stones are consists of stones of regular size, placed on the wooden structure. And after the piled stones were sealed with clay, tumulus was built with soil. Piled stones are unique characteristics which reflects the environment of Gyeongju area. Piled stone type wooden chamber tombs are located on the vast and plain river basin of Hyeongsan river(兄山江). Which makes vast source of sands and pebbles. Therefore, tumulus of these tombs contains large amount of sands and are prone to collapse if soil tumulus was built directly on the wooden structure. Consequently, to maintain external shape of the tumulus and to prevent collapse of inner structure, piled stones and clay-sealing was made. In this way, they can prevent total collapse of the tombs even if the tumulus was washed away. The soil tumulus is a characteristic which emerges when a nation or political entity reaches certain growing stage. It can be said that after birth of a nation, growing stage follows and social structure will change, and a newly emerged ruling class starts building new tombs, instead of precedent wooden chamber tombs. In this process, soil tumulus was built and the size and structure of the tombs differ according to the ruling class. Ground plan, stone embankments, number of the persons buried alive with the dead, quantity and quality of artifacts reflect social status of the ruling class. In conclusion, Gyeongju-style piled stone type wooden chamber tombs emerged with different characteristics from the precedent wooden chamber tombs when Shilla reached growing stage.

A Study on the Influence of the Water System on the Location and Spatial Structure of Hongju-seong (수체계가 홍주성의 입지와 공간구조 변천과정에 미친 영향)

  • Lee, Kyung-Chan;Kang, In-Ae
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.38 no.4
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    • pp.12-24
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    • 2020
  • The purpose of this study is to analyze the influence of the water system on the location, spatial structure, and construction method of Hongju-eupseong, centering on Hongjumok-eupchi. During the Joseon Dynasty, the water system in Hongjumok-eupchi is composed of artificially constructed Seong-an Runnel and ponds based on a branch-shaped natural waterways flowing from south to north and west to east. Compiling the results of various literature records, excavations and analysis of map data, it can be seen that the water system has an important influence on the construction of Hongju-seong. Firstly, Hongju-seong from the Goryeo Dynasty to the late Joseon Dynasty is located using a circular shape of topographical structure and a small erosion basin formed on the inner side of the Hongseongcheon and Wolgyecheon streams without significant change in location. In particular, Wolgyecheon and Hongseongcheon are natural moats, which are harmonized with Sohyangcheon and riverside topographical structures, affecting the location and construction method of Hongju-seong, water related facilities, and the spatial structure of eupseong. It is understood that location characteristic of Hongju-seong reflects the urban location structure harmonized with waterways in ancient China and Korea. Secondly in harmony with the water system and topographic structure of Hongju-seong, it is an important factor in deciding the land use of the town, the arrangement of the town hall facilities and inducing various non-subsidiary measures such as the establishment of embankment forest with a secret function and the closure of the south gate. In addition, artificial drainage facilities such as Seongan runnel and ponds are being actively introduced from early on to protect the walls or towns from flooding of Wolgyecheon. Especially there were typical methods for protecting the walls from water damage such as the Joseon Dynasty stone castle structure that was integrated with saturn(soil wall) in the Goryeo Dynasty, retreating wall in the northern gate area in the late Joseon Dynasty, and the method of constructing wall using korean tile and stone floors between reinforced soil layers in the western and northern wall.

Structural Behavior of the Buried flexible Conduits in Coastal Roads Under the Live Load (활하중이 작용하는 해안도로 하부 연성지중구조물의 거동 분석)

  • Cho, Sung-Min;Chang, Yong-Chai
    • Journal of Navigation and Port Research
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    • v.26 no.3
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    • pp.323-328
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    • 2002
  • Soil-steel structures have been used for the underpass, or drainage systems in the road embankment. This type of structures sustain external load using the correlations with the steel wall and engineered backfill materials. Buried flexible conduits made of corrugated steel plates for the coastal road was tested under vehicle loading to investigate the effects of live load. Testing conduits was a circular structure with a diameter of 6.25m. Live-load tests were conducted on two sections, one of which an attempt was made to reinforce the soil cover with the two layers of geo-gird. Hoop fiber strains of corrugated plate, normal earth pressures exerted outside the structure, and deformations of structure were instrumented during the tests. This paper describes the measured static and dynamic load responses of structure. Wall thrust by vehicle loads increased mainly at the crown and shoulder part of the conduit. However additional bending moment by vehicle loads was neglectable. The effectiveness of geogrid-reinforced soil cover on reducing hoop thrust is also discussed based on the measurements in two sections of the structure. The maximum thrusts at the section with geogrid-reinforced soil cover was 85-92% of those with un-reinforced soil cover in the static load tests of the circular structure; this confirms the beneficial effect of soil cover reinforcement on reducing the hoop thrust. However, it was revealed that the two layers of geogrid had no effect on reducing the overburden pressure at the crown level of structure. The obtained values of DLA decrease approximately in proportion to the increase in soil cover from 0.9m to 1.5m. These values are about 1.2-1.4 times higher than those specified in CHBDC.

Changes in Water Depth and Velocity by Debris around Piers (교각 주위내 부유잡목에 의한 수위 및 유속변화에 관한 연구)

  • Choi, Gye-Woon;Kim, Gee-Hyoung;Park, Yong-Sup
    • Journal of Korea Water Resources Association
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    • v.36 no.2
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    • pp.273-284
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    • 2003
  • In this paper, the reasons of damages and the case study are review in which bridge pier with debris accumulation, and safety Influence factors by debris around the bridge piers are review. Also experiment Is conducted for the characteristic of flow around piers by different area and angle of debris and the basic characteristics was review for safe design of bridge and embankments. As result of review of several standards of design, hydraulic structure's freeboard is simply decided by discharge, so it needs more detail standards. And as result of experiment, in the case of that water depth is deep and velocity is slow, variation of water depth Is more increase as increasing of debris. Therefore the variation regime of flow characteristics like velocity and water depth by debris is more large in the stream of small or medium size, which streams have large water depth and slow velocity so Froude Number Is expressed as small in the flood. Also when Froude Number is about 0.5, the water elevation is over freeboard in the standard if the debris over 20%. Therefore when hydraulic structure is constructed in the stream of small or medium size, it need to conduct more detail experiments about influence of debris, distribution of velocity and variation of elevation, and than the more safe freeboard will be presented using the experimental results.

Evaluation on Watershed Natural Habitat Assessment for Conservation of Brachymystax lenok tsinlingensis in Naerin Upstream (내린천 상류 유역 열목어(Brachymystax lenok tslingensis) 서식지 자연성 평가)

  • Jeong Eun Kim;Hwang Goo Lee
    • Ecology and Resilient Infrastructure
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    • v.10 no.3
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    • pp.73-84
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    • 2023
  • The objective of this study was to evaluate biodiversity and natural habitat environment of freshwater ecosystem. Our aim was therefore to produce a set of biodiversity and habitat indicators based on multi-parameters of water quality and biodiversity by analyzing the characteristics of the results by indicators. We selected four indicators a) anthropogenic disturbance, b) habitat diversity, c) biodiversity, d) ecosystem structure. The fishes cohabiting with Brachymystax lenok tsinlingensis were Rhynchocypris kumgangensis and Zacco koreanus. As a result of the anthropogenic disturbance evaluation, it was analyzed that vegetation embankment showed a more stable environment in the tributary than the main stream, and other disturbance was not confirmed As a result of the habitat diversity evaluation, it was analyzed that habitat evaluation index showed a high score of 200 more on average, showing an optimal habitat condition. As a result of the biodiversity evaluation, it was analyzed as a clean habitat condition with a high proportion of sensitive species, abundant dissolved oxygen, and little pollutants. As a results of the ecosystem structure, the ecological health condition metrics and appearance of endangered species showed large score deviation, but it was analyzed that the stream ecosystem health was generally excellent. There was a slight correlation between the habitat environment and the results of the nature habitat evaluation according to the appearance of the B. lenok tsinlingensis.

Effect of Water on the Lightweight Air-Mixed Soil Containing Silt Used for Road Embankment (도로성토체로 사용된 실트질 계열의 경랑기포혼합토에 대한 물의 영향)

  • Hwang, Joong-Ho;Ahn, Young-Kyun;Kim, Tae-Hyung
    • Journal of the Korean Geotechnical Society
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    • v.26 no.2
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    • pp.23-32
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    • 2010
  • This study was especially conducted to find out the characteristics of the lightweight air-mixed soil (slurry density 10 kN/$m^3$) containing silt related to water. Compression strength, permeability, and capillary height of the lightweight air-mixed soil were studied, and also to support these studies, the structure of that soil was analyzed in detail. Air bubbles of various sizes are inside the lightweight air-mixed soil, and its distribution in a location is almost constant. A numerous tiny pores are inside the air bubbles so that the lightweight air-mixed soil can be saturated with water. Porosity is also estimated through the image analysis. Peak strength of the lightweight air-mixed soil is not dependent on water, but behavior of stress-strain is affected by the water. Permeability is about $4.857{\times}10^{-6}cm/sec$, which is a little bit higher than the clay's permeability. Capillary rise occurs rapidly at the beginning of the test until the lapse of 100 minutes and then its increase rate becomes slow. The capillary rise causes the increase of the density of the lightweight air-mixed soil, and thus it is required to pay attention to this phenomenon during structure design and maintenance of the lightweight air-mixed soil.

Stress-Strain Characteristics of Weathered Granite Soil in Plane Strain Test (평면변형시험을 이용한 화강풍화토의 응력-변형률 특성)

  • Kim, You-Seong;Lee, Jin-Kwang;Kim, Jae-Hong
    • Journal of the Korean Geotechnical Society
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    • v.30 no.5
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    • pp.37-46
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    • 2014
  • Geotechnical structures have been analyzed and constructed in various geometry conditions to maintain their stability in accordance with the characteristics of construction design. Shear strengths are generally obtained from triaxial test to apply to design analysis. Geotechnical structures under strip loading, such as earth dam, embankment, and retaining wall, have the strain in a direction, and plane strain condition. Thus, an approximate shear strengths should be applied for stability analysis suitable to ground condition. When applying shear strengths obtained from triaxial tests for slope stability analysis, the evaluation of it may underestimate the factor of safety because the implementation is not suitable for geometry condition. The paper compares shear strengths obtained from triaxial test and plane strain test based on various relative densities using weathered granite soils. Additionally, yield stress is determined by maximum axial strain 15% in triaxial test because of continuous kinematic hardening, but plane strain test can determine a failure point in critical state to evaluate the shear strengths of soils at the second plastic hardening step. This study proposes to perform an appropriate test for many geotechnical problems with plane strain condition.

Ecological Management Plan Based on Environmental and Ecological Characteristics for the Tancheon Ecosystem Conservation Area in Seoul (서울시 탄천 생태계 보전지역의 환경생태특성을 고려한 생태적 관리계획)

  • Han Bong-Ho;Kim Jong-Yeop;Hong Suk-Hwan
    • Journal of the Korean Institute of Landscape Architecture
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    • v.32 no.5
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    • pp.84-101
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    • 2004
  • This study presents an ecological management plan for wildbird habitat conservation, an nature-friendly enhancement of bio-diversity using the riverside of the Tancheon Ecosystem Conservation Area in Seoul by analyzing environmental and ecological characteristics. As a result of analyzing actual vegetation, vegetation type was classified into 34 types. Humulus japonicus association covers an area of 441,568.6㎡(31.44%), and Artemisia princeps var. orientalis association covers an area of 89,690.1㎡(6.39%). Sandy plain as valuable wildbird habitat covers an area of 89,965.9㎡(6.4%). 125 taxa including 34 families, 93 genera, 107 species, and 18 varieties were recorded and the number of naturalized plants were 41 taxa at the survey site. Total naturalized index(NI) and urbanized index(UI) were recorded as 32.8%, and 15.5%. As a result of analyzing the herb plants association structure by surveying 8 belt-transects, the humid native plants was dominant in the partially adjacent revetment edge and damp riverside. On the other hand, naturalized plants was so extensively dominant that it was necessary to establish an ecological management plan. The observed wildbirds belonged to 50 species, 6,118 individuals, and 7 restricted species by law, which were Accipiter gentilis, Falco tinnunculus, Buteo hemilasius, and Buteo buteo. Oriolus chinensis,Hirundo rustica, and Alcedo atthis. The ecological administration plan for Tancheon Ecosystem Conservation Area as follows: in ecological land-use planning, the conservation area(695,518.5㎡) has native woody and herb vegetation and sandy plain with water as an wildbird habitat. The restoration area(653,702.7㎡) has a naturalized plants distribution are with artificial revetment. The nature-friendly Riverside Area(55,414.9㎡) was an easily approached area with damaged riverside vegetation, and a safe area to wildbird habitat. In riverside restoration planning, the artificial riverside should be restored to its natural riverside vegetation, and the artificial embankment should be restored with edge shrubs for wildbird habitat or revegetated for natural riverside landscape. For naturalized plants management planning, we selected naturalized plant species to be weeded out, and suggested an application method for ecological management.