• Geomechanics and Engineering
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• 제28권5호
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• pp.531-546
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• 2022

Ground displacements caused by the construction of overlapping twin shield tunnels with small turning radius are complex, especially under special geological conditions of construction. To investigate the ground displacements caused due to shield machines in the unique calcareous sand layers in Israel for the first time and determine the main factors affecting the ground displacements, field monitoring, laboratory geological analysis, theoretical calculations, and parameter studies were adopted. By using rod extensometers, inclinometers, total stations, and automatic segment-displacement monitors, subsurface tunneling-induced displacement, surface settlement, and displacement of the down-track tunnel segments caused by the construction of an up-track tunnel were analyzed. The up-track tunnel and the down-track tunnel pass through different stratum, resulting in different construction parameters and ground displacements. The laws of variation of thrust and torque, soil pressure in the chamber, excavated soil quantity, synchronous grouting pressure, and grout volume of the two tunnels from parallel to fully overlapping orientations were compared. The thrust and torque of the shield in the fine sand are larger than those in the Kurkar layer, and the grouting amount in fine sand is unstable. According to fuzzy statistics and Gaussian curve fitting of the shield tunneling speed, the tunneling speed in the Kurkar stratum is twice that in the fine-sand stratum.

• 대한토목학회논문집
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• 제14권1호
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• pp.195-202
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• 1994

본 연구에서는 모래의 전단파괴 포락선의 곡률특성을 구명하고 전단강도와 Been과 Jefferies가 제시한 상태정수간의 매개변수관계를 밝히기 위하여 많은 압밀배수삼축시험의 결과를 분석하였다. 통상적인 삼축시험에서 시료의 단면적 변화와 멤브레인의 영향에 대한 수정은 특히 한계상태를 결정하는데 중요하다고 할 수 있다. 실험결과로부터 전단강도를 밀도와 응력수준의 함수로 표현하는 모델을 제시하였고 모래의 전단파괴포락선의 곡률특성과 상태정수와 전단강도정수간의 관계를 밝혔다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.281-286
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• 2001

The development of automobile, vessel, rail road, and machine industry leads increase of foundry production used as their components, which cause a by-product, waste foundry sand (WFS). The amount of the WFS produced in Korea is over 900,000 ton a year, but most WFS buries itself and only 5~6% WFS is recycled as a material in construction materials. In this study, WFS is used as a fine aggregate for concrete. Five types of concretes aimed at the specified strength of 240$\pm$10 kgf/$cm^{2}$ , air contents of 4.5$\pm$1% and slump of 12$\pm$1.5cm were mixed with washed coarse seashore sand(WFS) in which salt was removed and then optimum mix proportion of concrete was determined. Moreover, basic properties such as setting time, workability, bleeding and slump loss of the fresh concrete with WFS were tested and compared with those of the concrete mixed without WFS. In .addition, both compressive strength of hardened concrete at each ages and tensile strength of it at the age of 28 days were measured and discussed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.223-228
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• 1997

In this study, bottom ash, lightweight aggregate, and Expanded Polystyrene was used to lighten the mortar. In order to compensate the reduction of strength caused by lightening, the waste foundry sand produced as solid waste was substituted for fine aggregate. As the device of reducing the ratio of absorption, the procedure of mixture was altered to check the effectiveness of surface coating of porous lightweight aggregate. It was observed over 170kg/$\textrm{cm}^2$ compressive strength at gravity about 1.3, an over 380kg/$\textrm{cm}^2$ at gravity about 1.7. the maximum strength was occurred when 30% of fine aggregate was replaced was replaced with waste foundry sand, and the ratio of absorption was decreased over 10% by changing the procedure of mixture.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.91-92
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• 2013

The strength of ultra-high-strength concrete can be reduced even if the spalling is prevented at a high temperature. Therefore, in this study, we measured internal temperature history and residual compressive strength using a 300×300×450mm short column specimens which use the fiber(NY 0.15+PP 0.10+SF 0.30vol·%) and respectively silica sand, washed sand, the slag sand. As a result, the temperature history and residual compressive strength are almost similar regardless of the fine aggregate types.

• 아시안잔디학회지
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• 제10권1호
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• pp.49-59
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• 1996

This report is researched on the cause and mechanism of soil erosion in comparison among Kwangnung, Mt. Kaya, Mt. Chili, and Mt. Soorak by physical and chemical analyses of their for- est soils. Clay, silt, and fine sand of Mt. Soorak are far less than those of Mt. Chili, Mt. Kaya, and Kwangnung area while coarse sand is very high level. The clay ratio of soil at Mt. Soorak is the most high level in comparison with that of other area. Denudation at Mt. Soorak, therefore, is cause of erosion by the result of transportation of soil particles. The eroding velocity increase for larger particle size and stronger cohesion between soil particles. Very fine sand, silt, and clay can be present in suspension near the bottom and the size of the particles in suspension depends upon the velocity of the current near the bottom and the roughness of the bottom. Key words: Theoretical analyses, Soil erosion and conservation, Forest soils.

• 한국환경보건학회지
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• 제26권2호
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• pp.41-48
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• 2000

This study has been carried out to determine the seasonal characteristics of concentration of various ionic (CI-, NO3-, SO42-, Na+, NH+, K+, Ca2+) and heavy metallic (Pb, Mn, Cu, Ni) species in Pusan from August 1997 to April 1998. The concentrations of CI-, Na+, K+ were higher during summer with 2.98 ${\mu}{\textrm}{m}$/㎥. Seasonal variation of total concentration of but the concentration of NH4+ was higher during winter with 2.46${\mu}{\textrm}{m}$/㎥. Seasonal variation of total concentration of heavy metals(Pb, Cu, Mn, Ni) were 186.0 ng/㎥ in summer, 222.6 ng/㎥ in autumn, and 135.83 ng/㎥ in winter. Over the seasons inspected, the concentration of Mn was higher in coarse particles than fine particles and concentration of Ni was higher in fine particles than coarse particles. during yellow sand period, the concentration of TSP was increased about two times than that of other period. SO42-, Ca2+ concentrations were higher than other ionic components because of soil particles. The concentration of Ni showed 94.62ng/㎥ was increased about 4~5 times than other period. Principal component of the yellow sand, SO42-, Ca2+ could be discreased by rainfall and washout effect of atmospheric aerosol was higher in coarse particles than fine particles. Results from PCA(principal component analysis) showed that major pollutant was NaCl by seasalt particulate and (NH4)2SO4.

• 콘크리트학회논문집
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• 제25권1호
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• pp.3-9
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• 2013

초고강도 콘크리트에서 잔골재로 세척사 대신에 전기로 산화 슬래그를 사용했을 경우, 재령 91일 압축강도가 약 15 MPa 정도 향상되었다. 압축강도가 향상된 원인을 규명하기 위해 잔골재의 Ca 성분 용출 특성을 고찰하였고, 잔골재와 페이스트 계면에서의 미세조직, 기공율, 미소경도 및 Ca/Si 몰비를 검토하였다. 그리고 잔골재 형상에 의한 강도 증진 효과를 알아보기 위해 잔골재의 표면 거칠기를 AFM으로 측정하였다. 실험 결과, 초고강도 콘크리트에서 전기로 산화 슬래그 잔골재 사용에 의한 강도 증진 기구는 화학적 기구와 물리적 기구로 구분할 수 있다. 화학적 기구로는, 전기로 산화 슬래그에서 함유되어 있는 가용성 Ca 성분이 용출되어 잔골재와 페이스트 사이에 반응생성물을 형성시켜 조직을 치밀화 시킴으로 잔골재-페이스트간의 부착력을 증진 시키는 것으로 나타났다. 그리고 물리적 기구로는, 전기로 산화 슬래그 잔골재는 세척사에 비해 표면의 굴곡도가 2배 정도 커서, 잔골재와 페이스트 간의 interlocking strength를 증가시킴으로서 압축강도 발현에 기여하는 것으로 판단했다.

• 레미콘
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• 10호통권69호
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• pp.2-11
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• 2001

This paper describes the feasiblity of recycling sewage dredged soils as fine affrefate. This paper describes the feasibility of recycling sewage dredged soils as fine aggregate. The specific gravity of the dredged soils was smaller than that of sand due to the effect of dredged sludge. However, the grain size distribution of the dredged soils is relative well graded, and the results of the heavy metal concentration from the leaching test of the dredged soils was significantly lower than the requirements of the allowable criteria. Therefore, the effect of recycling of dredged soils on environment the as fine aggregate was negligible. Also, the specific gravity of the dredged and washed soils was similar to that of sand, and the dredged and washed soils for the most part showed lower heavy metal leaching characteristics than those of dredged soils, Also, the results of the study for evaluation the recycling feasibility of dredged and washed soils as fine affrefate. The organic impurity content of the dredged and washed soils was lower than the requirements of the Korean industrial Standards, and the mortar compressive strength using the washdredged soils also met those of the Korean industrial Standards. And, the strengths of the dredged and washed soils were over 95% of those of the NaOH-treated samples. Therefore, it is expected that the dredged soils will be able to be an alternative for fine aggregate.

• 한국건축시공학회지
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• 제21권6호
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• pp.551-562
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• 2021

본 연구에서는 IGCC에서 발생하는 부산물인 CGS를 콘크리트용 혼합 잔골재로써 효율적으로 활용하는 방안을 제시하기 위하여 플라이애시 치환 매스 콘크리트의 수화열 저감 효과를 확보하기 위한 방안으로 CGS 기반 혼합 잔골재와 플라이애시 치환에 따른 수화열 저감 특성 분석 및 해석을 실시 하고자 한다. 따라서, 매스 콘크리트의 수화열 저감을 위하여 활용되는 플라이애시 기반 저발열 결합재에 CGS를 잔골재로 치환하여 최적의 조합으로 FA 30% 및 CGS를 잔골재로 50% 치환할 경우 저발열 결합재 FA를 단일 치환한 경우보다 복합상승 효과에 따라 수화열 저감 성능이 더 크게 나타났다. 따라서 산업부산물인 CGS 골재 조합에 플라이애시를 복합 치환한 분체-골재조합 재료 시스템은 매스 콘크리트 수화열 저감 공법의 효율적인 대안으로서 활용이 기대된다.