• Advances in concrete construction
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• 제2권1호
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• pp.13-27
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• 2014

The principal objective of this study is to deepen the characterization studies already led on sand concretes in previous works. Indeed, it consists in studying the effect of the sand type on the main properties of sand concrete: fracture and mechanical properties. We particularly insist on the determination of the fracture characteristics of this material which apparently have not been studied. To carry out this study, four different types of sand have been used: dune sand (DS), river sand (RS), crushed sand (CS) and river-dune sand (RDS). These sands differ in mineralogical nature, grain shape, angularity, particle size, proportion of fine elements, etc. The obtained results show that the particle size distribution of sand has marked its influence in all the studied properties of sand concrete since the sand having the highest diameter and the best particle size distribution has given the best fracture and mechanical properties. The grain shape, the angularity and the nature of sand have also marked their influence: thanks to its angularity and its limestone nature, crushed sand yielded good results compared to river and dune sands which are characterized by rounded shape and siliceous nature. Finally, it should further be noted that the sand concrete presents values of fracture and mechanical properties slightly lower than those of ordinary concrete. Compared to mortar, although the mechanical strength is lower, the fracture parameters are almost comparable. In all cases, the sand grains are debonded from the paste cement during the fracture which means that the crack goes through the paste-aggregate interface.

• International Journal of Concrete Structures and Materials
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• 제9권3호
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• pp.381-390
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• 2015

Investigating the microstructure of hardened cement mixtures with the aid of advanced technology will help the concrete industry to develop appropriate binders for durable building materials. In this paper, morphological, mineralogical and thermogravimetric analyses of autoclave-cured mixtures incorporating ground dune sand and ground granulated blast furnace slag as partial cementing materials were investigated. The microstructure analyses of hydrated products were conducted using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), differential thermal analysis (DTA), thermo-graphic analysis (TGA) and X-ray diffraction (XRD). The SEM and EDX results demonstrated the formation of thin plate-like calcium silicate hydrate plates and a compacted microstructure. The DTA and TGA analyses revealed that the calcium hydroxide generated from the hydration binder materials was consumed during the secondary pozzolanic reaction. Residual crystalline silica was observed from the XRD analysis of all of the blended mixtures, indicating the presence of excess silica. A good correlation was observed between the compressive strength of the blended mixtures and the CaO/$SiO_2$ ratio of the binder materials.

• Journal of Forest and Environmental Science
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• 제18권1호
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• pp.31-44
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• 2001

우리나라 해안림(海岸林)의 다면적(多面的) 기능(機能)과 시대적(時代的) 가치관(價値觀)의 변화를 파악하고, 해안사방(海岸砂防)의 참고자료를 얻기 위해 일본의 해안림과 해안사방에 대한 각종 자료를 수집하고 있다. 따라서 일본(日本) 산형현(山形縣)의 장내해안림(庄內海岸林)을 중심으로 분석, 정리하였으며, 주요내용은 장내해안림(庄內海岸林)의 환경특성(環境特性), 연혁과 현황, 문제점, 장내지역(庄內地域)의 방풍림대(防風林帶)와 해안사방시설(海岸砂防施設) 등이다.

• 한국환경과학회지
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• 제12권2호
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• pp.125-132
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• 2003

This study was executed by China along with the Tumen river, which formed border of North Korea and China. As a result 91 family, 282 genera, 363 species, 57 variety 4 species, total 424 taxa of vascular plants were identified. The examination area was include the region that had various vegetation such as upper swampy land, seashore dune, a river, a high mountain grassy plain, deciduous tree zone, evergreen coniferous forest zone. The followings are representative plants, which found in an examination area but not in South Korea. Picea koraiensis, Larix gmelini var. principis-ruprechtii, Betula playphylla, Ulmus pumila, Populus koreana, Ledum palustre var. diversipilosum, Rhododendron parvifolium, Salix brachypoda, Phacelurus latifolius, Carex gotoi, Carex capricornis, Calla palustris, Aquilegia flabellata var. pumila, Lilium davuricum, Astragalus membranaceus, Trifolium lupinaster, Ledebourieila seselodeds, Polemonium racemosum, Scutellaria baicalensis, Linnaea borealis, Thladiantha dubia, Inula helenium, Trollius hondoensis, Hypocaeris ciliata, Aconitum kirinense, Aconitum arcuatum, Potentilla viscosa var. macrophylla. And there are 21 rare and endangered species, which Korean Forest Sevice designated, such as Aconitum koreanum, Acorus calamus var. angustatus, Polygonatum stenophyllum, Drosera rotundifolia, Iris setosa, Jeffersonia dubia, Lilium davuricum, Lilium cernum, Paeonia obovata, Penthorum chinense, Phacelurus latifolius, Rosa marretii, Sparganium stoloniferum, Thymus quinquecostatus, Trillium tschonoskii, Utricularia japonica, Tripterospermum japonicum, Vaccinium uliginosum, Vaccinium vitis-idaea, etc. Especially, plants like, Acanthopanax senticosus, Jeffersonia dubia and Lillum cernum which have high values of ornamental, and medical use are in an extinction crisis. High swampy land was formed to upper stream of Tumen river. It showed representative vegitation, like Carex sp., Scirpus radirans, Eriophorum latifolium. Wetlands plant and a dune plant were mixed in down stream area of Tumen river. On a dune, seashore plants, such as Carex kobomugi, Salsola collina, Raphanus sativus var. raphanistroides, Rosa rugosa, Scutellaria strigillosa, Linaria japonica, Phacelurus latifolius were appeared frequently.

• 자원환경지질
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• 제7권3호
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• pp.87-100
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• 1974

This paper deals with grain size analysis, heavy mineral analysis and trace element analysis of the recent sediments of Han River basin between Cheongpyong, Gyeonggi province and Seoul. For each location the samples are taken at river shoreline, river berm and river dune. The size analysis discloses that the mean values range from $-1.37{\phi}$ to $-1.60{\phi}$, sorting values range from 0.25 to 1.84, skewness values range from -0.44 to 0.51 and kurtosis values range from -0.1 to 1.75. Based on the textural parameters, the dune sand can be distinguished from the shoreline-berm sand. The content of heavy minerals of each sample ranges from 0.04 to 4.7%. The principal heavy minerals are ilmenite, magnetite, leucoxene, garnet, amphibole, pyroxene, kyanite, zircon, monazite, tourmaline, epidote, limonite, and minor minerals are apatite, sillimanite, andalusite and olivine. In general, dune sand samples contain more heavy minerals than the samples of shoreline or berm sand. This suggests that the heavy mineral concentration is affected by wind action more than by any other causes. The content of ilmenite and leucoxene decreases, whereas the content of zircon and epidote increases as it approaches the downstream region. The differences result from the variance of geological occurrences. The emission spectrochemical analysis and colorimetry analysis revealed that the content of Ni and V in the heavy minerals of the study area are higher than those of other stream sediments in Korea. On the other hand the content of Cu, Ph, Zn, Mo, W, P, Mn, Cr, Ag and Sn are lower in the study area. It has been observed also that the contents of all the elements except for Bi are higher in this area than the samples of marine sediments of Yellow Sea.

• 한국환경생태학회지
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• 제20권1호
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• pp.41-51
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• 2006

우이도 해안사구의 식물상을 조사한 결과, 52과 108속 124종 15변종 3품종 총 142종류가 확인되었다. 식물구계학적 특정식물종에는 3등급에 갯그령, 솔장다리, 틸머위 3종류, 1등급에 갯쇠보리, 통보리사초, 갯방풍, 모래지치 등의 사구식물들과 후박나무, 보리밥나무, 해국 등의 해안식물들이 포함되어 총 16종류가 확인되었다. 또한, 귀화식물에는 7과 10속 11종류로 조사되었으며, 총 출현하는 식물상에 대한 귀화율은 약7.8%로 분석되었다. 식생군집 조사 중 돈목해안지역에는 2002년도에 전체 피복율이 약$20%{\sim}25%$정도가 확인되었으나, 본 조사에서는 $65%{\sim}75%$로 3배 이상의 사구식물들이 높게 출현하였다. 성촌해안지 역 또한 2002년도 조사에서는 식생 피복율이 $15%{\sim}20%$ 정도이었으나, 본 조사에서 왕잔디와 통보리사초가 급속도로 증가하여 전체 피복율이 $70%{\sim}75%$정도로 증가하였다. 풍성사구 지역은 강한 바람과 모래의 유출유입이 반복되면서 사구식물의 종수나 개체수가 단조로운 경향을 나타냈다.

• 한국지형학회지
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• 제19권4호
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• pp.109-122
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• 2012

충남 보령시 소황리 해안을 대상으로 지난 2년간 전사구의 지형변화과정을 분석하였다. 이를 위해, 연구지역에서 식생 및 바람 자료를 획득하고 7개의 횡단면과 1개의 고정조사구($20m{\times}50m$)에서 지형변화를 정기적으로 조사하였다. 사구의 성장은 주로 늦겨울에서 봄 사이에 활발하였으며, 북서풍이 강한 시기와 일치하였다. 특히, 3월부터 4월까지 전사구 전면부에 퇴적이 증가하였으며, 해안선에서 25m까지 최대 30cm 두께로 모래가 쌓였다. 강풍의 증가와 식생의 생장이 모래의 이동과 퇴적을 견인한 것으로 분석되었다. 한편, 태풍이나 사리에 의해 해수면이 일시적으로 상승할 때, 사구지대의 하부가 침식되었다. 사빈-사구 경계부가 바닷물에 의해 직접적인 영향을 받지만, 일부 구간에서는 사구 전면부 전체가 영향을 받아서 사구단애가 형성되기도 하였다. 하지만 시간이 지남에 따라 침식단면은 원래의 모습을 회복하였다.

• 한국지형학회지
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• 제25권2호
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• pp.43-61
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• 2018

Heterogeneous sedimentary deposits with different soil colors and various degree of hardness are exposed in its foredune and tidal zone due to the effects of recently accelerated coastal erosion along the Ujeon Coast in Jeung-do, Shinan-gun. This study was conducted on the assumption that these sedimentary deposits were developed in different timing and environments. Thus, we can infer the geomorphic development processes of the area based on evidences like the physicochemical characteristics of each sedimentary layer. Several analysis of these sedimentary depositssuch as grain size analysis, X-ray Fluorescence Measurement (XRF), and Loss on ignition (LOI) were performed on central (Ujeon A) and southern (Ujeon B) parts of the Ujeon Coast. I found that the foredune sedimentary deposits have four stages of geomorphic development processes. In the initial stage of development, during the peak of the Last Interglacial Period (MIS 5e), basal deposits were accumulated in the low-energy environment of subtidal zones. In the second stage, during the Last Glacial Period (MIS 4~MIS 2), eolian sedimentary layers were developed by terrestrial aeolian processes by which fine materials were transported from the Yellow Sea which became a dry land exposed by lowered sea level. In the third stage, various mechanism existed for the formation of each sedimentary layer. In the region of Ujeon A, sedimentary layers were developed in the littoral zone environment dominated by marine processes during the maximum phase of transgression in the Holocene. Meanwhile, the region of Ujeon B began to form eolian sedimentary layers during MIS 2. In the last stage, thick coastal dune deposits, covered all over the Ujeon Coast. During the late Holocene (0.7~0.6 ka), terrestrial processes kept dominating the region, developing typical eolian sedimentary layers.

• 한국지형학회지
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• 제25권2호
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• pp.63-80
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• 2018

The purpose of this study was to investigate the physicochemical characteristics and formation age of sand dunes in the Okjukdong and Dajindong, Daecheong Island. As a result, most of the sand deposited in Okjukdong were composed of medium sized sand with moderately well sorted. The $SiO_2$ and $Al_2O_3$ accounted for a very high proportion of these deposits. There were some differences in characteristics between the sands in the dune and beach, whereas similar characteristics were observed among the materials (OJ-B, OJ-C and OJ-D) in the dune. In case of Dajindong, heterogeneous geochemical characteristics were found in the lower point. It was estimated that this was due to the influence of Daejin-dong black beach. Age dating results showed that uncovered dunes in Okjukdong were deposited $0.44{\pm}0.02$ ~ $0.50{\pm}0.02ka$, and sand depositsin Dajindong were formed $0.16{\pm}0.01$ ~ $0.18{\pm}0.01ka$. In both Okjukdong and Dajindong, sand deposits estimated to be formed 70 years ago, therefore it can be estimated that sand movement was active throughout the area from about hundred years ago. In this study area, the growth of sand dunes has been active in recent several decades or hundred years. It seems that there were different regions where deposits predominated over time. The source of dune sand was also different from time to time. Since the windbreak forest was established, the natural growth of sand dunes was limited, and sand nourishment was carried out by period. Therefore, in order to protect and continuously utilize coastalsand dunesin Daecheong Island, it is necessary to prepare conservation plan.

• 한국지형학회지
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• 제24권1호
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• pp.25-38
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• 2017

To investigate the characteristics of sand sediment topography in the Yeonggwang coastal area of Chonnam and to collect evidence of the past extreme events causing coastal flooding, three sites were surveyed among the sediments of Baeksoo-eup Hassari. In this study, the changes of particle characteristics, chemical composition, and the age of deposition of sediments were investigated. The sediments near Baeksoonam Elementary School at the elevation of 10m near the paleo-coastline are estimated to have been deposited at about 3,400 years ago and the grain size of the upper part of the sandy layer is in the range of $2.47-2.11{\varphi}$. The burial age of the sediment layer at Sadeung junction(BSN-B) was about 100 years. Considering the distance from the current coastline, the sands forming the dune are estimated to have been moved or deposited from the nearby area or the other dune on the front side. The mean grain size is observed to be fining upward. Especially, the mean of the upper part is about $2.3{\varphi}$, which is similar to other survey points. The averaged grain size of the lower part of the BSNC (Hasari-1 Gu) was $2.196{\varphi}$ and the upper part was $2.16{\varphi}$. The sorting showed that the upper part was slightly poorer than the lower, and it was difficult to specify the change of the environment. The burial age of the lower layer, which contains shells, was about 300 years. Considering previous studies, this shell layer is presumed to have formed by coastal flooding, such as a storm surge.