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그라우트 재료로서 광물찌꺼기 혼화재의 활용 가능성 평가
김대현,노정두,강성승,Kim, Daehyeon,Noh, Jeongdu,Kang, Seong-Seung 한국암반공학회 2016 터널과지하공간 Vol.26 No.2
전남 해남에 위치한 ${\bigcirc}{\bigcirc}$광산의 광물찌꺼기를 이용하여 그라우트 재료로서의 활용 가능성을 평가하였다. 광물찌꺼기의 광물학적 특성을 살펴보기 위하여 XRD 분석을 실시하였다. 또한 광물찌꺼기와 시멘트를 3가지 비율로 혼합한 그라우트 재료의 물리적 및 역학적 특성을 살펴보기 위하여 양생기간에 따른 흐름도, 탄성파속도, 일축압축강도 시험을 각각 실시하였다. XRD 분석 결과에 의하면 본 광산의 광물찌꺼기는 대부분 석영, 방연석, 황철석 등의 광물들로 구성된 것으로 나타났다. 흐름시험 결과는 광물찌꺼기의 혼합비율이 높아질수록 흐름도가 감소하는 경향을 보였다. 탄성파속도는 흐름도와 마찬가지로 양생기간에 관계없이 광물찌꺼기의 혼합비율이 높아질수록 낮아지는 경향을 보였다. 일축압축강도 및 탄성계수 또한 양생기간에 관계없이 광물찌꺼기 혼합비율이 증가할수록 작아지는 경향을 보였다. 광물찌꺼기를 혼합한 그라우트 주입재의 물리적 및 역학적 특성만을 고려할 때 이들 결괏값은 그라우트 재료로서 충분히 활용 가능성을 가지고 있다고 판단된다. 하지만 광물찌꺼기내에 방연석과 황철석 등 금속광물이 포함되어 있어 지반 내 주입 시 환경오염을 일으킬 수 있으므로 향후 이에 대한 대책방안이 고려되어야 할 것으로 사료된다. The purpose of this study is to evaluate the applicability of tailing in the ${\bigcirc}{\bigcirc}$ mine as a grout material. For the purpose, XRD analysis was performed for mineralogical properties of tailing. In addition, flow, velocity, and uniaxial compressive strength tests were carried out for physical and mechanical properties of a grout material with the mixing ratio of cement and tailing and curing periods. By the result of XRD analysis, tailing of the mine was found to mostly consist of quartz, galena, and pyrite. The flow observed by the flow test showed decreasing tendency with increasing the mixing ratio of tailing. The velocity was also lowered with increasing the mixing ratio of tailing regardless of curing periods. The uniaxial compressive strength as well as Young's modulus also show a tendency to decrease with increasing the mixing ratio of tailing independently on the curing periods. Considering only the physical and mechanical properties of a grout material with tailing, the results are considered to be sufficiently used as a grout material. However, since metallic minerals such as galena and pyrite in tailing contents and these are causing environmental contamination, countermeasures should be considered for this problem in future.
니켈 나노입자의 레이저기반 소결을 통한 유연성 전도성 전극 가공
김대현(Daehyeon Kim),이한종(Hanjong Lee),문상흔(SangHeun Moon),이창민(ChangMin Lee),구상모(Sangmo Koo) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Recently, the importance of processing techniques on a flexible substrate is emerging. In particular, as the application of flexible devices has expanded, research on fabrication for electrically conductive patterns on this diverse substrate, especially on polymers, has been performed. In this study, it is noted that nickel has a higher resistance to oxidation than copper. The nickel nanoparticle-based ink was synthesized and sintered on the Polydimethylsiloxane(PDMS) substrate through laser-direct writing. Nickel conductive patterns processed on flexible substrates retain their shape and properties despite mechanical deformation (e.g., bending). It was confirmed that the electrical properties were also maintained for a long time under oxidizing conditions. Therefore, it was utilized in applications such as flexible heaters, and it will be possible to expand to more applications.
사질토 지반에서 수평하중에 따른 단일강관말뚝의 거동특성에 관한 실험적 연구
김대현(Kim, Daehyeon),이태광(Lee, Tae-Gwang),김선학(Kim, Sun-Hak) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.5
해상풍력기초를 설계함에 있어 사용하중에 대해 극한적인 조건뿐만 아니라 지속적인 동적하중에 대해 기초의 거동을 정확하게 파악하여 안정적이고 경제적인 기초를 개발할 필요성이 있다. 이를 위하여 강관말뚝을 일정비율로 축소시켜 모형 말뚝을 제작하고, 모형토조에 모래층을 500mm의 높이로 포설한 후 모형말뚝을 모델링하여 정적 및 반복 수평재하실험을 실시하였다. 그 결과, 정적수평재하시 모형말뚝의 길이/직경(L/D)이 클수록 하중에 따른 변위는 증가하는 반면, 반복수평재하 시 하중재하 횟수가 증가할수록 반복수평하중 1회당 발생하는 말뚝의 수평변위는 감소하였고 지반이 조밀할수록 반복수평하 중에 의한 말뚝의 극한수평지지력의 증가율이 작아지는 것으로 나타났다. 또한 휨모멘트의 분포형상은 지반의 상대밀도에 상관없이 유사한 형태를 보였으며, 최대휨모멘트는 지표면으로부터 170mm지점에서 발생하는 것으로 나타났다. 그리고 지반 의 상대밀도가 증가할수록 정적수평재하와 반복수평재하 조건에서 발생하는 최대휨모멘트는 증가했다. In order to fulfill the needs of reliable and economically feasible foundation, engineers should consider not only the working load that can endure extreme conditions but also apprehending precise behavior of continuous dynamic load while designing the foundation of offshore wind power generators. To actualize the foundation, a model pile was made in miniature. Also, calibration chamber was made and a 500mm height of sand-bed was made to perform “static lateral load experiment” and “repetitive loading experiment”, total of two Lateral load tests. As a result, in Static Lateral load test, the bigger length/diameter of model pile led an increase in load displacement. However, when performing “Cyclic Lateral load test”, the increase in number of under loading led the decrease in horizontal displacement from each repeated lateral load. While performing Static Lateral load test and repeated loading experiment, we could observe the decreasing in the rate of ultimate lateral load capacity increase of the pile. Also, it turned out that the higher relative density of the ground, the lower ultimate lateral load capacity by repeated horizontal loading.
광양지역의 항타강관말뚝의 목표신뢰성지수 및 저항계수 산정
김대현(Daehyeon Kim),김현태(Hyeon-Tae Kim),임재춘(Jae-Choon Leem),김성헌(Sung-Heon, Kim),이증빈(Cheung-Bin Lee) 한국지반신소재학회 2013 한국토목섬유학회 학술발표회 Vol.2013 No.11
Recently, the necessity of developing the load and resistance factor design(LRFD) for soft ground improvement method has been raised, since the limit state design is requested as international technical standard for the foundation of structures. In this study, to develop LRFD codes for foundation structures in Korea, target reliability index and resistance factor for static bearing capacity of driven steel pipe piles were calibrated in the framework of reliability theory. The 16 data(in Gwangyang) and the 57 dada(Korea Institute of Construction Technology, 2008) sets of static load test and soil property tests conducted in the whole domestic area were collected along with available subsurface investigation results. As a result, to prepare the introduction of the LRFD from international technical standard, considering the nature of Korea a resistance coefficient from working stress design method was suggested. We created the foundation of the resistance factor design. The result from this research will be the useful information for developing various foundation and soil structure under LRFD.
김대현(Daehyeon Kim),박경호(Kyung-Ho Park),이태광(Tae-Gwang Lee) 한국지반신소재학회 2013 한국토목섬유학회 학술발표회 Vol.2013 No.11
Pile foundation of foundation structure is generally used as deep foundation form that the load of upper structure is safely delivered to the firm lower part ground. This pile foundation structure is widely used in large construction or civil engineering structures. Displacement or destruction of the pile foundation will impact directly on the stability of repeated horizontal load. It is very import to consider this characteristic of horizontal load when building a pile foundation. When designing the fundamental structure that withstands heavier loads than itself, horizontal load become the critical design factor. In this research, we analyzed the effects of different pile types on bending moment and bearing capacity of the pile foundation. Based on the analyses, the closed ended pile type is better than the open ended pile type in terms of resisting horizontal load.