• 한국산학기술학회논문지
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• 제13권10호
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• pp.4863-4868
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• 2012

모래지반에 설치된 무리말뚝 중 두 개의 말뚝에 대하여 하중재하시험을 실시하고 그 결과를 하중전이법을 적용한 해석결과와 비교 분석하였다. 무리말뚝 설치 후 무리말뚝의 중앙부에 위치한 말뚝에 대한 해석결과에 따르면 하중지지능력이 재하시험결과보다 작게 나타났는데 주된 원인은 무리말뚝 설치로 인한 지반조밀화로 생각된다. 또한 API 방법과 Coyle and Sulaiman 방법을 적용하여 구한 하중-침하곡선으로부터 Davisson 방법을 통해 구한 말뚝의 극한지지력은 재하시험에 의한 극한지지력 값의 각각 77%와 90%였다. 무리말뚝 설치로 인한 지반 조밀화의 영향을 비교적 덜 받은 가장자리 말뚝에 대한 재하시험결과와 해석결과를 비교할 때 Davisson 방법을 통해 구한 말뚝의 극한지지력은 API 방법과 Coyle and Sulaiman 방법에 의할 경우 재하시험결과에 의한 값에 비해 각각 1.1배와 1.3배의 값을 보였다.

• 한국도로학회논문집
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• 제17권4호
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• pp.53-61
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• 2015

PURPOSES : The objective of this study is to evaluate the SDAR (solvent deasphaltene residue), which is obtained from the solvent deasphalting (SDA) process, as a pavement material. METHODS : The physical properties of the SDAR were evaluated based on its chemical composition, and asphalt mixtures with the SDAR were fabricated and used for the evaluation of mechanical properties. Firstly, the chemical composition of SARA (saturate, aromatic, resin and asphaltene) was analyzed using the TLC-FID (thin-layer chromatography-flame ionization detector). Moreover, the basic material properties of the asphalt binder with the SDAR were evaluated by the penetration test, softening point test, ductility test, and PG (performance grade) grade test. The rheological properties of the asphalt binder with the SDAR were evaluated by the dynamic shear modulus ($G^*$) obtained using the time-temperature superposition (TTS) principle. Secondly, the mechanical properties of the asphalt mixtures with the SDAR were evaluated. The compactibility was evaluated using the gyratory compacter. Moreover, the tensile strength ratio (TSR) was used for evaluating the moisture susceptibility of the asphalt mixtures (i.e., susceptibility to pothole damage). The dynamic modulus $E^*$, which is a fundamental property of the asphalt mixture, obtained at different temperatures and loading cycles, was used to evaluate the mechanical properties of the asphalt mixtures. RESULTS AND CONCLUSION : The SDAR shows stiffer and more brittle behavior than the conventional asphalt binder. As the application of the SDAR directly in the field may cause early failures, such as cracks on pavements, it should be applied with modifiers that can favorably modify the brittleness property of the SDAR. Therefore, if appropriate additives are applied on the SDAR, it can be used as a pavement material because of its low cost and strong resistance to rutting.

• 대한토목학회논문집
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• 제28권1D호
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• pp.35-43
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• 2008

본 연구는 지난 4년간 한국도로공사 시험도로 아스팔트 포장의 주요 손상인자의 정량화와 그 변화를 다루고 있다. 포장상태조사 장비인 ARAN(Automatic Road Analyzer)을 이용하여 준공 직후인 2002년 12월부터 2006년 10월까지 총 5차례에 걸쳐 아스팔트 전단면에 대해 노면상태를 측정하고 소성변형, 균열손상, 그리고 종단평탄성을 중심으로 그 결과를 분석하였다. 실내시험을 통해 시험도로의 아스팔트 혼합물의 온도와 하중 재하속도에 대한 선형점탄성 거동을 비교하고, 표층용 혼합물인 ASTM 19mm에 대해서는 동탄성계수에 미치는 공극률의 영향도 검토하였다. 일반 밀입도 표층 단면의 차륜부에서 추출한 시편의 공극률을 측정하여 시험도로 포장의 다짐도 변화를 추정하였으며 이를 바탕으로 다짐도-포장 손상의 관계를 검토하였다. 교통하중과 포장 손상과의 연관성 분석 결과 소성변형과 균열을 포함한 노면 손상의 증가는 교통하중이 재하되는 시기와 바로 일치하지는 않았으며 오히려 온도와 같은 환경에 더 영향을 받는 것으로 관측되었다. 반면에 노면 평탄성은 공용년수가 증가 하면서 교통하중에 민감하게 반응하였으며 환경인자와의 상관성은 매우 낮은 것으로 나타났다.

• 대한토목학회논문집
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• 제26권2C호
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• pp.89-98
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• 2006

본 연구에서는 해성점토의 전단강도를 증진시킬 목적으로 철과 알루미늄 전극을 직접 삽입한 후 전극을 분해하여 지반 고결화 효과를 유발하였다. 이를 위해 남해안에서 채취한 실제 해성점토에 대해 실내 토조를 이용한 파일럿 실험을 실시하였고, 각각 철과 알루미늄을 삽입한 후 일정 고전류(2.5A)를 적용시켰다. 고결화에 의한 영향을 파악하고자 실험 종료 후에는 콘관입시험기를 이용하여 비배수 전단강도를 측정하였으며, 위치별 함수비와 pH 및 전기전도도를 측정하여 철과 알루미늄의 전극분해에 의한 고결화 효과를 간접적으로 판단하였다. 철 전극 전기분해 실험 결과, 양(+)극부 근처에서의 함수비는 초기에 비해 35% 감소하였고, 음극부 근처에서는 13% 증가하였으나, 양극부에서 용출된 철 이온과 흙 입자의 고결화 작용에 의해 전체적으로 측정된 전단강도는 초기에 비해 상당히 증가하였다. 또한 알루미늄 전극을 이용하였을 경우, 철에 비해 비교적 균일한 전단강도 증진효과가 나타났으며, 그 개량정도 역시 더 크게 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 연약지반처리위원회 학술세미나
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• pp.1-13
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• 1999

The use of Compaction Grouting evolved in the 1950's to correct structural settlement of buildings. Over the almost 50 years, the technology has developed and is currently used in wide range of applications. Compaction Grouting, the injection of a very stiff, 'zero-slump' mortar grout under relatively high pressure, displaces and compacts soils. It can effectively repair natural or man-made soil strength deficiencies in variety of soil formations. Major uses of Compaction Grouting include densifying loose soils or fill voids caused by sinkholes, poorly compacted fills, broken utilities, improper dewatering, or soft ground tunneling excavation. Other application include preventing liquefaction, re-leveling settled structures, and using compaction grout bulbs as structural elements of minipiles or underpinning. The technique replaced slurry injection, or 'pressure grouting', as the preferred method of densification grouting. There are several reasons for the increased use of Compaction Grouting which can be summarized in one word: CONTROL. The low slump grout and injection processes are usually designed to keep the grout in a homogeneous mass at the point of injection, while acceptable in some limited applications, tends to quickly get out of control. Hydraulic soil fracturing can cause extensive grout travel, often well beyond the desired treatment zone. So, on the basis of the two case history constructed in recent year, a study has been peformed to analyze the basic mechanism of the Compaction Grouting and verify the effectiveness of the ground improvement using some test methods.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1173-1180
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• 2006

In this study, aluminum electrodes were put in marine clay which was taken from the south coast in Korea to increase the undrained shear strength by inducing the densification and cementation between clay particles and precipitates which were developed by electric decomposition in an electrode. To raise the cementation rate and reduce treatment time, high electric current (2.5A) was applied in each electrode at a semi-pilot scale soil box with marine clay. After the tests, the undrained shear strength was measured at designated points using a static cone penetration test device and sampling was conducted simultaneously in order to measure water content, pH and electric conductivity which would be the key for configuring the cementation effects indirectly. In the results of electric decomposition in aluminum electrode, the measured shear strength was increased considerably compared to the initial shear strength because of the cementation effect between iron ions and soil particles.

• 대한토목학회논문집
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• 제13권5호
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• pp.201-208
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• 1993

지구측위사스템(GPS)의 등장은 새로운 기준점망의 구성과 기설망의 해석, 강화, 고밀도화의 작업에 신속성과 경제성을 부여할 수 있게 되었으며, 열악한 기상조건에서도 지도제작, 지적측량, 건설공사의 기준점 설정에서의 적용이 가능하기에 이르렀다. 이 논문에서는 GPS 측량기법의 실용화에 목적을 두고 있으며 기존의 EDM 방식에 의한 정밀기준점 측량을 대체할 수 있는 지를 검토하였다. 정밀 1차 기준점망인 평군변장 10 km의 시범망을 Wild GPS-System 200에 의해 관측하고 이 거리와 EDM 거리 및 실용성과와를 비교분석하였으며 상대고저차를 평균해면상의 값으로 변환코자 하였다. 연구결과를 종합해 보면, 국가기준점망의 구성에 있어 GPS를 하나의 새로운 관측장비로 취급하는 기법에 의하여 기존의 망구성과 계산체계를 유지할 수 있으므로 기존의 측량기법을 대체할 수 있음이 제시되어 있다.

• 한국분말재료학회지
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• 제13권6호
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• pp.408-414
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• 2006

[ $MoSi_2$ ] alloys with Al, B or Nb were prepared by an advanced consolidation process that combined mechanical alloying with pulse discharge sintering (complex forming) to improve the mechanical properties. Their microstructure and mechanical properties were investigated. The $MoSi_2$ alloys fabricated by complex forming method showed very fine microstructure when compared with the sample sintered from commercial $MoSi_2$ powders. Alloys made from powders milled in Ar gas had fewer silica or alumina phases as compared to their counterparts sintered from powders milled in air. In densification of the sintered body, addition of B was more effective than Al or Nb. Both Victors hardness and tensile test indicated that the alloy fabricated by the complex forming method showed better properties than the sample sintered from commercial $MoSi_2$ powders. The Al added alloy sintered from the powders milled in air had the superior mechanical properties due to the suppression of $SiO_2$ and formation of fine $Al_2O_3$ particles.

• ETRI Journal
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• 제37권6호
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• pp.1065-1076
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• 2015

Network densification is regarded as the dominant driver for wireless evolution into the era of 5G. However, in this context, interference-limited dense small cell deployments are facing technical challenges in mobility management. The recently announced results from an LTE field test conducted in a dense urban area show a handover failure (HOF) rate of over 21%. A major cause of HOFs is the transmission failure of handover command (HO CMD) messages. In this paper, we propose two enhancements to HO performance in LTE networks - radio link failure-proactive HO, which helps with the reliable transmission of HO CMD messages while the user equipment is under a poor radio link condition, and Early Handover Preparation with Ping-Pong Avoidance (EHOPPPA) HO, which assures reliable transmission of HO CMD under a good radio link condition. We analyze the HO performance of EHOPPPA HO theoretically, and perform simulations to compare the performance of the proposed schemes with that of standard LTE HO. We show that they can decrease the HOF rate to nearly zero through an analysis, and based on the simulation results, by over 70%, without increasing the ping-pong probability.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.913-922
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• 2009

Fourteen model pile load tests using a calibration chamber and instrumented model pile were preformed to investigate the variation of the behaviors of driven piles in sands with soil and lateral cyclic loading conditions. Results of the model tests showed that the first loading cycle generated more than 70% of the pile head rotation developed for 50 lateral loading cycles. Lateral cyclic loading also made an increase of the ultimate lateral load capacity of piles for $K_0$=0.4 and an decrease for $K_0$ higher than 0.4. Higher portion of the increase or decrease in the ultimate lateral load capacity by lateral cyclic loading was generated for the first loading cycle due to densification of loosening of the soil around the pile by lateral cyclic loading. It was also observed that a two-way cyclic loading caused higher ultimate lateral load capacity of driven piles than a one-way cyclic loading. When the pile was in the ultimate state, the maximum bending moment developed in the pile increased with increasing $K_0$ value of soil and was insensitive to the magnitude and number of lateral cyclic loading.