• 한국환경복원기술학회지
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• 제20권2호
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• pp.79-91
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• 2017

This study was conducted to find out the physical properties and soil shearing strength reinforcement effect of herbaceous plants for the slope revegetation works. Two native plants(Pennisetum alopecuroides and Miscanthus sinensis) were used for this experiment, because they have excellent seed germination rates without preconditioning, and grow naturally around rivers. To identify the physical properties, the partial dry weight of plants were investigated. To identify the soil shearing strength reinforcement effect, the respective soil shearing strengths of the control soils, Pennisetum alopecuroides, Miscanthus sinensis samples were measured. Also, we did a correlation analysis to examine the relation of shearing strength to plant features. The results are summarized as follows: 1. The average dry weight of Pennisetum alopecuroides samples consists of 52.36% above ground and 47.64% at root. And in dry weight, 78.24% of it's root distributes within 10 cm in soil depth. Meanwhile the average dry weight of Miscanthus sinensis samples consists of 52.91% above ground and 47.09% at root. And in dry weight, 82.95% of it's root distributes within 10 cm in soil depth. 2. The results of correlation analysis showed that for both Pennisetum alopecuroides and Miscanthus sinensis, it could not be said that there was any correlation between shearing strength and plant characteristics, and statistically they were not meaningful. 3. In the shearing strength test with control soils, Pennisetum alopecuroides, Miscanthus sinensis as subjects, the differences in shearing strength measurement results were modest, and the order was shown as control soils < Pennisetum alopecuroides < Miscanthus sinensis, so the soil shearing strength reinforcement effect by the Pennisetum alopecuroides and the Miscanthus sinensis on loamy sand at river banks surface was confirmed.

• 한국지반신소재학회논문집
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• 제13권1호
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• pp.71-83
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• 2014

부산지역은 낙동강 하구에 위치하여 퇴적층, 매립층 등이 매우 잘 발달되어 있어 지진이 발생한다면 이러한 지층 등에서 증폭현상이 나타나 모래층과 성토층 및 매립지반에 액상화 발생 가능성이 매우 커진다. 만약 액상화가 발생한다면 지진에 의한 피해는 크게 가중되어 막대한 피해를 야기 시키게 된다. 그러므로 본 연구는 지진 발생 시 항만시설의 1차 보호구조물인 부산항 신항 방파제의 안정성을 검토하기 위하여, 국내 내진설계기준과 항만 및 어항 설계기준을 바탕으로 인공지진과 국내에 널리 사용되는 장주기 지진파와 단주기 지진파인 포함하여 지진규모 5.6~7.9 수준의 지진 13개 등을 사용하여 첫 번째로 여러 제시된 액상화 평가방법을 이용하여 방파제 하부 치환모래층의 액상화 발생 가능성을 검토하여 안정성을 평가하고, 두 번째 지진규모에 따른 지진에너지와 가속도 응답스펙트럼에 대한 특성분석을 수행하여 설계기준에 근접하는 지진파 제시하며, 세 번째 제시된 지진파를 이용하여 방파제의 동적 안정성을 검토하기 위해 유한요소해석을 실시하여 구조물의 안정성을 확인하고, Geotextile에 발생하는 변위 및 인장력의 변화에 대하여 확인하였다. 따라서 본 연구결과 방파제 하부 치환모래층에 대한 액상화 발생가능성과 방파제의 동적수평변위 및 Geotextile의 변화는 하부지반(치환모래층)에 의해 매우 큰 영향을 받는 것으로 나타났다.

• 한국건축시공학회지
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• 제3권4호
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• pp.79-86
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• 2003

The purpose of study is to offer base data for high fluid concrete mix property, as grasp effect of aggregate to reach much more effect for producing high fluid concrete. For this study, there are three types of combined aggregates, river sand + river aggregate(type A), river sand + crusted aggregate(type B), washed sea sand + crushed aggregate(type C) and take a factor, water-contents, water-binder ratio and S/a. And so, we had following conclusion, resulting application-ability of high fluid mortar by K-slump tester to use a handy consistency measuring instrument. And so, we had following conclusion, resulting application-ability of high fluid concrete by K-slump tester to use a handy consistency measuring instrument. 1) In cafe of regular water binder ratio, high fluid concrete suffered much effect of combined aggregates and water binder ratio. Range of water binder ratio by combined aggregates is w/b 0.4 downward(type A and B), w/b 0.35 downward(type C). 2) Water contents to need for producing high fluid concrete is minimum 170kg/$\textrm{m}^3$ without regard to combined aggregates. 3) The effect of S/a on high fluid concrete by combined aggregates is approximately S/a 50% (type A and B), s/a 50-55% (type C). 4) Consistency measuring of high fluid concrete by K-slump tester is possible and first indication value, high fluid concrete can be produced, is 6~10.5cm.

• Advances in concrete construction
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• 제5권6호
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• pp.671-683
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• 2017

Commonly used concrete in general, consists of cement, fine aggregate, coarse aggregate and water. Natural river sand is the most commonly used material as fine aggregate in concrete. One of the important requirements of concrete is that it should be durable under certain conditions of exposure. The durability of concrete is defined as its ability to resist weathering action, chemical attack or any other process of deterioration. Durable concrete will retain its original form, quality and serviceability when exposed to its environment. Deterioration can occur in various forms such as alkali aggregate expansion, freeze-thaw expansion, salt scaling by de-icing salts, shrinkage, attack on the reinforcement due to carbonation, sulphate attack on exposure to ground water, sea water attack and corrosion caused by salts. Addition of admixtures may control these effects. In this paper, an attempt has been made to replace part of fine aggregate by tailing material and part of cement by fly ash to improve the durability of concrete. The various durability tests performed were chemical attack tests such as sulphate attack, chloride attack and acid attack test and water absorption test. The concrete blend with 35% Tailing Material (TM) in place of river sand and 20% Fly Ash (FA) in place of OPC, has exhibited higher durability characteristics.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.3-44
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• 1999

This paper discusses the lateral behavior of single and group piles in homogeneous and non-homogeneous(two layered) soil. In the single pile, the model tests were conducted to investigate the effects on ratio of lower layer height to embedded pile length, ratio of soil modules of upper layer to lower layer, boundary rendition of pile head and tip, embedded pile length, pile construction condition, ground condition with saturate and moisture state in Nak-Dong river sand. Also, in the group pile, the model tests were to investigate the effects on spacing-to-diameter ratio of pile, pile array, ratio of pile spacing, boundary condition of pile head and tip, eccentric load and ground condition. The maximum bending moment and deflection induced in active piles were found to be highly dependent on the relative density, pile construction condition, boundary condition of pile head and tip. Based on the results obtained, it was found that the decrease of lateral bearing capacity in saturated sand was in the range of 31% - 53% as compared with the case of dry sand. Also, in the group pile, a spacing-to-diameter of 6.0 seems to be large enough to eliminate the group effect for the case of relative density of 61.8%, and 32.8%, and then each pile in such a case behaves essentially the same as a single pile. In this study, the program is developed by using the modified Chang method which used p - y method and the exact solution of governing equation of pile and it can be used to calculate the deflection, bending moment and soil reaction with FDM in non-homogeneous soil. In comparing the modified Chang method with field test results, the predict results shows better agreement with measured results in field tests.

• 한국지형학회지
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• 제27권2호
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• pp.29-46
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• 2020

In this study, changes in the fluvial landforms of the Yeoju section of the Han River, which was made up of the Han River Restoration Project, were examined through existing previous research data, government's environmental impact assessment data, satellite images, and field observations. For example, In the vicinity of Dori Island, the most upstream part of the study section, the location of the confluence of the Han River and Cheongmi Stream was changed, and it was found that a significant portion of the sand sedimentary layer disappeared. In the Bawuinupgubi area, the wetland, which is the first class in the ecological nature, was greatly modified, and the elevation of the ground rose as Gangcheon island and it was completely separated from the river by dredging The confluence of Geumdangcheon and the point bar of Yeonyang-ri in the south were also dredged, turned into an artificial waterfront park, and a chute channel remained in the form of a wetland was also developed as a recreational park. The deposional forms around Baekseok-ri islands also disappeared as dredging was carried out. Among the areas adjacent to the confluence of Bokcheon and Yangchon-ri Island, some sedimentay forms remains, but the abandonned channel between Yangchon-ri and the northern river bank has been changed into a riverside reservoir through dredging and embankment construction, and the waterway of the tributary river(Yazoo) has been greatly changed.

• 한국철도학회논문집
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• 제9권4호
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• pp.493-498
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• 2006

In this study, two large pile load tests were performed in the deep sand gravel deposit of Nakdong river basin so that the characteristics of the load transfer was identified. The fully instrumented rectangular barrette pile in the size of $1.5\times3.0m$ and the circular bored pile of the diameter 1.5 m were placed into the ground below 50 m. Under the applied loads of 2,400 tonf and 4,000 tonf, the test results of the load transfer showed the portion of 83% and 93% of the applied loads on the barrette pile and the bored pile, respectively, were supported by the skin friction along the pile shaft. It was revealed that the most of these skin friction mobilized in sand layer underlying clay layer having N-value more than 30 and that the friction per unit area of the bored pile was larger than the friction of barrette pile. However, if embedded in the stiff sand graval layer, the both piles were proven to be sufficient for using as the friction piles.

• Computers and Concrete
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• 제10권4호
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• pp.349-360
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• 2012

In this paper, compressive strength, water permeability and abrasion resistance of concretes containing high volume fine fly ash (FFA) and fine ground palm oil fuel ash (GPA) were studied. Portland cement type I was replaced with FFA and GPA at dosages up to 70% by weight of binder. Ground river sand (GRS) was also used to replace Portland cement in order to indicate the level of filler effect. Results indicated that FFA was slightly more reactive than GPA. The replacement of 40-70% of FFA produced concretes with compressive strength, permeability and abrasion resistance comparable to those of normal concretes. The incorporation of GPA slightly reduced the performances of concretes as compared to those of FFA concretes. The reduction of Portland cement was partly compensated by the increase in pozzolanic activity of the fine fly ash and palm oil fuel ash and thus enabled the large replacement levels.

• 한국구조물진단유지관리공학회 논문집
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• 제5권3호
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• pp.225-231
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• 2001

When building tunnels beneath riverbeds where very large quantities of groundwater inflow exist, added to high water head the soil supporting conditions are very poor because the soil consists of sand and silt, etc. It is necessary to have grouting and mini pipe roof installed in the region for ground reinforcement to decrease permeability. According to this result of horizontal boring and laboratory soil testing, ground reinforcement was achieved by L.W grouting for range of 3.0 times the tunnel radius, to increase stability of the tunnel we used the ling-cut method, 0.8m for one step excavation, shotcrete with 25cm thick, steel lib with H-$125{\times}125$. and a temporary shotcrete invert 20cm thick was installed to prevent deformation of the tunnel.

• 한국수자원학회논문집
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• 제44권10호
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• pp.797-807
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• 2011

국내 하천에서 사주 상 식생 활착 현상이 급속하게 진행되고 있다. 1960년대 산업화와 도시화 이전 우리나라 하천은 모래, 자갈이대부분인이른바 'White River (백사장하천)'이었으나, 1970년대이후댐건설, 하천정비등으로유황과유사이 송특성이 교란되어수변에 식생이번무하게 되는이른바 'Green River (식생하천)'가진행중이다. 본 연구는비조절하천사주 상 식생활착에 영향을 미치는 인자 중에서 수위, 수온, 강우, 토양수분, 토양입경 등의 상호연관성을 파악하고자하였다. 이를 위해 우리나라 모래하천인 내성천의 하류를 시험하천구간으로 선정하고, 289일간 모니터링 및 조사 분석을 실시하였다. 또한 과거로부터 현재까지 식생의 경년변화를 파악하기 위해 1970년부터 2009년까지의 항공사진을 분석하였다. 시험하천구간의 범위는 횡단길이 361m, 종단길이 약 2 km이다. 조사 분석 결과 내성천 시험하천구간은 지하수위가 하천수위보다 20~30 cm 가량 높게 나타나는 이득하천이었다. 지하수온은 일별, 계절별 차이가 $5^{\circ}C$ 미만이었고, 하천수온은 식생활착이 본격적으로 시작되는 5월부터 $10^{\circ}C$ 이하로 떨어지지 않았다. 토양수분의 영향인자는 하층은 지하수위, 상층은 강우이며, 상하층은 모두 토양입경에 영향을 받는 것으로 나타났다. 토양수분측정지점 6곳의 지표면~지하 1m까지의 토양은 $D_{50}$ 입경 0.07~1.37mm의 모래이며, 이 입경에서 가능한 모세관 높이는 약 14~43 cm 범위로 추정된다. 한편 비 조절하천인 시험하천구간의 40년간 공간분석 결과, 인위적인 하천교란과 가뭄은 식생활착을 촉진하며, 홍수로 인해 식생군락이 자주 소멸될 수 있음을 확인하였다. 1970년부터 식생의 크고 작은 활착과 소멸이 반복되고 있지만 현재의 식생면적은 과거에 비해 뚜렷하게 증가되어 있다. 식생면적은 시간에 따라 점진적으로 증가하고 있는 것으로 판단된다.