• 산업기술연구
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• 제28권B호
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• pp.91-99
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• 2008

Applicability of existing methods of predicting consolidation settlement was assessed by analyzing results of centrifuge tests modelling self-weight consolidation of soft marine clay. From extensive literature review about self-weight consolidation of soft marine clays located in southern coast in Korea, constitutive relationships of void ratio-effective stress-permeability and typical self-weight consolidation curves with time were obtained by centrifuge model experiments. For the condition of surcharge loading, exact solution of consolidation settlement curve was obtained by Terzaghi's consolidation theory and was compared with the results predicted by currently available methods such as Hyperbolic method, Asaoka's method, Hoshino's method and ${\sqrt{S}}$ method. All methods were found to have their own inherent error to predict final consolidation settlement. From results of analyzing the self-weight consolidation with time by using those methods, Asaoka's method predicted the best. Hyperbolic method predicted relatively well in error range of 2~24% for the case of showing the linearity in the relationship between T vs T/S in the stage of consolidation degree of 60~90 %. For the case of relation curve of T vs $T/S^2$ showing the lineality after the middle stage, error range from Hoshino method was close to those from Hyperbolic method. However, Hoshino method is not able to predict the final settlement in the case of relation curve of T vs $T/S^2$ being horizontal. For the given data about self-weight consolidation after the middle stage, relation curve of T vs T/S from ${\sqrt{S}}$ method shows the better linearity than that of T vs $T/{\sqrt{s}}$ from Hyperbolic method.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1342-1351
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• 2011

Nowadays rolling stock has become a fast and convenient transportation and increased in its demands. But the improvement of speed has result in increase of aerodynamic noise and therefore residential districts near by the railroad are now constantly suffering from the racket. Thus the study regarding rolling stock's environmental noise measurement and appraisal has become important. The case of environmental noise, there are no changes of tone so prediction can be made by reducing areas around the railway. This is part of the study which estimates the noise around the railway using scaled model, and the source of the noise has been researched on. The scaled model of rolling stock will have to be able to make high frequency and it needs to be spread out in a short amount of time. When popping a balloon or firing a gun fits its condition and this study analyzed the characteristics of these two different noises. Measurement was held on a wide vacant lot and the reflection effect of the ground is additionally examined. It is judged to be used in the future when predicting the environmental noise of railway vehicles.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.214-220
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• 2003

Pipe jacking is a name for a method to excavate a tunnel by pushing pipe into the ground from an especial pit. Size of tunnels in this method is different from under 900mm (microtunneling) to more than 3,000mm. Method of excavation is also different from hand digging to use of any kind of tunnel boring machines such as slurry and earth pressure balance (EPB) machines. Slurry pipe jacking was firmly established as a special method for the nondisruptive construction of the underground tunnels in urban area. During the pipe jacking and microtunneling process, the jacking load is an important parameter, controlling the pipe wall thickness, need to and location of intermediate jacking station, selection of jacking frame and lubrication requirements. The main component of the jacking load is due to frictional resistance. In this paper the skin friction between pipe surface and surrounding condition also lubricant quality based on a few fundamental tests, were considered. During this study unconfined compressive strength test, dynamic friction measurement test and direct shear box test were raised for one of the largest diameter slurry pipe jacking project in Fujisawa city in Japan. It could be concluded that in slurry pipe jacking, prediction of frictional forces are mainly dependent on successful lubrication, its quality and lubricant strength parameters. Conclusions from this study can be used for the same experiences.

• 환경영향평가
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• 제21권2호
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• pp.289-296
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• 2012

The shock vibration such as machine vibration, blasting vibration etc. has effect on nearby structure as well as human body. The purpose of this study is to predict allowable limit distance of vibration about human body. First of all, vibration velocity such as PPV, PVS was measured by shock vibration experiment, and vibration level was calculated by conversion formula of vibration velocity. And then, allowable limit distance was analyzed by converted vibration level. The results are as follows : Firstly, the correlation coefficient of converted vibration level was over R=0.94, and vibration level caused by PVS was usually represented to high curve line. Secondly, the cross point of vibration level between ground and concrete condition was represented to 66.68dB(V), and allowable limit distance was represented to difference over three times when vibration regulation was raised from 65dB(V) to 80dB(V).

• 한국추진공학회지
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• 제18권3호
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• pp.1-7
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• 2014

친환경 추진제인 액체메탄을 연료로 사용하는 이원추진제 로켓엔진의 이론성능분석을 통해 엔진의 설계변수를 도출하였다. 엔진의 연소성능 예측을 위해 CEA를 활용한 화학평형해석을 수행하였으며, 추진제 혼합비 및 연소실 내부압력에 따른 연소성능 특성을 고찰하였다. 엔진의 특성길이 도출을 위해 1차원 액적기화모델을 적용하여 성능변수 변화에 따른 추진제의 기화시간을 계산하였으며, 지상연소 이론성능분석을 통해 메탄 이원추진제 로켓엔진의 설계제원을 제시하였다.

• Geomechanics and Engineering
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• 제9권5호
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• pp.585-599
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• 2015

Laboratory model tests were conducted to investigate the effect of surcharge loading rate on the magnitude of lateral displacement of prefabricated vertical drains (PVDs) improved deposit. The test results indicate that under the condition that the system had sufficient factor of safety (FS) ($FS{\geq}1.2$), for the similar model ground under the same total applied surcharge load, the lateral displacement increases with the increase of loading rate. The test results have been used to check the validity of a previously proposed method for predicting the maximum lateral displacement, and it shows that the data points are around the middle line of the predicted range, which supports the usefulness of the proposed method. The basic idea of the prediction method is an empirical relationship between the normalized lateral displacement (NLD) and a ration of load to the undrained shear strength of the deposit (RLS). The model test results offer some modifications of the NLD-RLS relationship: (1) instead of a bilinear relationship, NLD-RLS relationship may be entirely nonlinear; (2) the upper bound value of RLS for the proposed method can be used may be limited to 2.1 instead of the originally proposed value of 3.0.

• Journal of Biosystems Engineering
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• 제25권3호
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• pp.195-202
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• 2000

This study was conducted to recognize a possibility that cone index can be used as a means of evaluating the tillage workability. Cone indexes were measured every 24 hours after rainfall at the experimental plots, and the rotary and plowing operations were conducted at the same time. The workability was evaluated on a basis of three categories of good, fair and poor depending on the quality of the performed works. Although the workability was affected by many factors such as soil type, moisture content ground slope and weather condition, the duration and amount of rainfall were of most influence. Results of the study showed that a good workability was resulted from the cone indexes greater than an average of 552 kPa for rotary operations and 671 kPa for plowing operations. Fair work was obtained with cone indexes greater than an average of 331 kPa for rotary operations and 459 kPa for plowing operations. The cone indexes less than an average of 171 kPa and 149 kPa resulted in poor workabilities for rotary and plowing operations, respectively. The experimental results may provide a general guideline for evaluating the tillage workability by cone index.

• 대한토목학회논문집
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• 제31권6D호
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• pp.839-848
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• 2011

TBM(Tunnel Boring Machine) 터널은 굴진 도중 장비의 교체나 개조 등은 불가능하기 때문에 굴진 종료 시까지 투입된 장비로 굴진하여야만 한다. 특히 토압식 쉴드TBM은 막장관찰이 어려우므로 굴진 중에 수집된 자료를 분석하여 지반상태의 변화를 예측하고 이를 시공에 반영하여야한다. 지금까지의 TBM에 대한 연구는 굴착 대상이 되는 지반의 특성에 따른 장비선정 및 굴진속도 예측모델 개발이 주로 이루어져왔다. 그러나 굴착의 주체가 되는 TBM 장비의 굴진자료에 의한 지반상태의 추정 및 운전방법의 개선에 초점을 맞춘 연구는 그리 많이 수행되지 않았다. 본 연구는 토압식 쉴드TBM 시공 사례에서 얻은 굴진자료를 활용하여 투입된 장비의 운전조건에 따른 굴진속도의 변화와 최적 운전조건에 대해 알아보았다. 본 연구의 결과를 요약하면 다음과 같다. 첫째, 커터헤드의 회전속도와 총추력이 굴진속도에 가장 큰 영향을 주며 둘째, 적정한 굴진속도를 위해서는 최적 회전속도를 유지하면서 총추력을 조정하는 것이 좋으며 셋째, 총추력의 증가 추세에 따라 지반조건의 변화에 대한 예측이 가능하여 이에 따라 적절한 운전조건의 변경을 결정할 수 있다.

• 한국화재소방학회논문지
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• 제24권4호
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• pp.18-26
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• 2010

강우 후 경과일수에 따른 연료습도 변화는 산불위험도 예측과 산불감시원 활용에 매우 중요하다. 따라서 이러한 산불위험 조건을 구명하기 위해 2007년 봄철 영동지방 소나무림에서 임분 밀도별로 5mm 이상 강우 후 지표에 떨어져 있는 고사한 나뭇가지의 직경이 0.6cm 이하, 0.6~3.0cm, 3.0~6.0cm, 6.0cm 이상에 대한 연료습도변화 예측모델을 개발하였다. 연구결과 지표연료의 직경이 작고, 소임분일수록 연료습도의 감소가 빠르게 진행되었으며 산불위험 연료습도에 도달하는 날짜도 소임분 직경 0.6cm 이하의 경우 2일차, 직경 0.6~3.0cm의 경우 3일차로 나타났다. 이러한 결과를 토대로 각 직경별 연료습도변화 예측모델($R^2=0.76{\sim}0.92$)을 개발하였으며, 2008년 동일기간의 강우 후 기상 실측자료를 적용하여 예측모델을 검증한 결과 1% 수준에서 유의성이 있음을 알 수 있었다.

• 터널과지하공간
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• 제15권2호
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• pp.111-118
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• 2005

연구지역은 옥천변성대에 속하며 단층파쇄대가 터널굴착방향과 평행하게 존재하여 막장면의 자립성 저하 및 이에 따르는 터널 주변지반의 이완 등으로 터널 내에 과도한 변위가 발생하였다. 이에 따라 단층파쇄대의 영향범위를 파악하고 특성을 분석하기 위하여 TSP(Tunnel Seismic Prediction)탐사를 수행하였다. 또한 막장면 조사와 시추조사를 병행 실시하여 거동원인을 분석하고 전방 파쇄대의 예측을 통하여 터널 굴착 및 지보에 영향을 주는 지질구조대나 용수대의 위치와 규모를 확인하였다. 조사결과를 토대로 터널형상 및 그에 따른 지층상태를 3차원으로 모델링 하였다. 모델링된 개체 내에 포함된 여러 변수(함유량, 물성치, 암반등급 등 모든 정량적인 수치)는 지구통계학적 기법을 통해 분석하였다. 모델링 결과를 분석하면 단층파쇄대에 의한 풍화대의 분포가 터널우측을 중심으로 발달하면서 좌측으로 그 범위가 감소하고 있다. 단층파쇄대는 주향 $N0\~5^{\circ}E$, 경사 NW의 방향성을 가지며, 여러 개의 지질이상대를 포함한 대규모의 파쇄대로 이루어진 것으로 확인되었다. 터널내 과대 변위는 해당구간에 밀집된 불연속면의 상호교차 및 단층대에 의한 터널 좌우측 암반강도 불균형으로 편하중이 발생한 것으로 판단되며 그라우팅 등의 터널보강공법이 필요한 것으로 판단된다.