• Title/Summary/Keyword: ground model test

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A Study on the Restraint Effect on Lateral Displacement of an Inclined Earth Retaining Structure Integrated with Soil Nailing in Sandy Ground (사질토지반에 설치된 소일네일 복합형 IER의 수평변위 억제효과에 관한 연구)

  • Park, Tae-Keon;Im, Jong-Chul;Yoo, Jae-Won;Kim, Chang-Young;Kang, Sang-Kyun;Lee, Woo-Je
    • Journal of the Korean Geotechnical Society
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    • v.33 no.10
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    • pp.33-47
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    • 2017
  • A self-supported temporary excavation method called IER is normally applicable to excavation depth ranging from 6.0 m to 7.0 m though the method depends on ground condition and overburden load. Combining IER with another method is required in deeper excavation depth in order to maintain the structural stability of the IER. In this study, we performed model tests and 3D FE analysis to check the stability of the IER adopting soil nailing method, and to propose its effective installation method. The lateral displacement of the IER using soil nailing decreased by 92% of that of IER without soil nailing. Optimum design is possible for both economic feasibility and stability when interval spacing and length of soil nails is $1.5m(S_h){\times}0.75m(S_v)$ and 86% of excavation depth, respectively. Excavation depth using IER increases 1.71 times by adopting soil nailing in increment of lateral displacement of IER right before the last excavation stage.

A Study on the Seismic Performance of Energy-Dissipating Sacrificial Devices for Steel Plate Ginder Bridges (강합성 거더교에 적용된 희생부재형 에너지소산장치의 내진성능에 관한 연구)

  • Cho, Kwang-Il;Gwak, Pil-Bong;Mha, Ho-Seong;Kim, Sang-Hyo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.11 no.3 s.55
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    • pp.87-96
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    • 2007
  • A new Energy-Dissipating Sacrificial Device (EDSD) is developed for steel plate girders, which can effectively dissipate the energy stored in the structures during seismic actions. To verify the performance of the EDSD, various seismic responses of a sample bridge with the EDSD are analyzed in terms of energy, member forces and deformation. The full scale model tests are conducted to certify the performance of the EDSD when it is applied on existing bridges. Using the improved hysteretic model of the sacrificial member, the seismic analysis for an example bridge is performed. The results show that the proposed EDSD under seismic excitations can significantly decrease the energy stored in the bridge structures and reduce the relative displacements of each superstructure to the ground. The EDSD is also found to function as a structural fuse under strong ground motions, sacrificing itself to absorb the excessive energy. Consequently, economical enhancement of the seismic performance of bridges can be achieved by employing the newly developed energy-dissipating sacrificial device.

Interactions between pre-existing large pipelines and a new tunnel (기존 대구경 파이프라인과 신설터널간의 상호작용)

  • Jeong, Sun-Ah;Choi, Jung-In;Hong, Eun-Soo;Chun, Youn-Chul;Lee, Seok-Won
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.2
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    • pp.175-188
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    • 2009
  • When a new tunnel is excavated by the drill and blast method near pre-existing underground structures or tunnels due to the region restricted condition such as urban area, the ground will be relaxed by the excavation. In this case, issues can be created in terms of stability of pre-existing underground structures. One of major factors determining the stability of pre-existing underground structures can be a separation distance between pre-existing underground structures and a newly excavated tunnel. The region of ground relaxation defined by the plastic zone due to new excavation can be varied by separation distance. In this study, in other to estimate an influence of new tunnel excavation in terms of separation distance on the stability of pre-existing large pipelines, two-dimensional scaled model tests using plaster were performed for six models which have a different separation distance, The results show that based on the analysis of induced displacement during tunnel construction, the displacement decreases as the separation distance between large pipeline and new tunnel is increased until the distance is 2.5 times of pipeline diameter. Beyond this point, however, the displacement has become stabilized.

A Physical Model Test on Behavior of Shield-tunnel Lining according to Drain Conditions (배수조건에 따른 쉴드터널 라이닝의 거동연구를 위한 모형실험)

  • Choi, Gou-Moon;Yune, Chan-Young;Ma, Sang-Joon
    • Journal of the Korean Geotechnical Society
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    • v.30 no.5
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    • pp.55-65
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    • 2014
  • Most shield tunnels are designed based on the assumption of a undrained condition. But they are operated as drained tunnels in which underground water flows and passes through a drainage facility. Therefore, it is necessary that the drainage condition be considered in the shield tunnel design. In this research, new testing device which can simulate the underground tunnel located below ground water level, was developed. Total stress and pore water pressure were examined and an inflow water into an inner pipe was measured using the testing device. Test results showed that the total stress, which was the sum of effective stress and pore pressure, increased more in an undrained condition and an inflow water into an inner pipe was proportional to the water pressure but inversely proportional to the loading stress. Consequently, if the drainage is considered in the shield tunnel design, the more economical design can be expected because of the stress reduction of the lining.

A Study on the Application of GFRP Rock Bolt Sensor through Field Experiment and Numerical Analysis (현장실험과 수치해석을 통한 GFRP 록볼트 센서의 적용성 연구)

  • Lee, Seungjoo;Chang, Suk-Hyun;Lee, Kang-Il;Kim, Bumjoo;Heo, Joon;Kim, Yong-Seong
    • Journal of the Korean Geosynthetics Society
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    • v.18 no.4
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    • pp.129-138
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    • 2019
  • In this study, the rebar rock bolt sensor and GFRP rock bolt sensor, which can be monitored, were embedded in a large model slope, and the behavior of slopes occurred in the early stage of slope collapse was analyzed after performing the field failure test, numerical analysis of the individual element method and finite element method. By comparing and analyzing the field test and numerical analysis results, field applicability of rock slope collapse monitoring on the rebar rock bolt sensor and GFRP rock bolt sensor was investigated. Through this study, smart slope collapse prediction and warning system was developed, which can be used to induce effective evacuation of residents living in the collapsible area by detecting landslide and ground decay precursor information in advance.

Effect of tractor travelling speed on a tire slip

  • Kim, Yeon Soo;Lee, Sang Dae;Kim, Young Joo;Kim, Yong Joo;Choi, Chang Hyun
    • Korean Journal of Agricultural Science
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    • v.45 no.1
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    • pp.120-127
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    • 2018
  • The rural labor force has gradually been decreasing due to the decrement of the farm population and the increment of the aging population. To solve these problems, it is necessary to develop and study autonomous agricultural machinery. Therefore, analyzing the dynamic behavior of vehicles in an autonomous agricultural environment is important. Until now, most studies on agricultural machinery, especially on ground vehicle dynamics, have been done by field tests. However, these field test methods are time consuming and costly with seasonal restrictions. A research method that can replace existing field test methods by using simulations is needed. In this study, we did basic research analyzing the effect of the travelling speed of a tractor on tire slip using simulation software. A tractor simulation model was developed based on field conditions following a straight path. The simulation was done for three ranges of speed: 20 - 30 km/h (considered the normal travelling speed range), 6 - 8 km/h (considered the plow tillage speed range) and 2 - 4 km/h (considered the rotary tillage speed range). The results of the simulation show that the slip ratio and slip angle values tended to increase as the traveling speed range of the tractor decreased. From the simulation results, it can be concluded that at low tractor speeds, it becomes more difficult to control the vehicle path. In future research, simulations will be done with various work environments such as a curved path as well as with various friction coefficient conditions, and the simulation results will be experimentally verified by applying them to an agricultural tractor.

Cold Tolerance Assessment of Ever Ground-cover Plants for Extensive Green Roof System (저관리형 옥상녹화를 위한 상록 지피식물의 내한성 평가)

  • Zhao, Hong-Xia;Li, Hong;Son, Hee-Jun;Kang, Tai-Ho
    • Journal of the Korean Institute of Landscape Architecture
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    • v.40 no.4
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    • pp.127-134
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    • 2012
  • This study was carried out to suggest an experimental base in selecting the cold tolerance of plants. The cold tolerance of the plants were subject to laboratory low temperature treatments and cold processing time were evaluated using both electrolyte leakage and regrowth test. The Logistic model of nonlinear regression analysis was used to evaluate the lethal temperatures that were predicted with the range of $-16.1{\sim}-24.4^{\circ}C$. The order of low-temperature resistance was Sedum reflexum > S. spurium > Ophiopogon japonicus > S. album > S. takevimense > Dianthus chinensis. At the lowest temperature of $13.4^{\circ}C$ the electrolyte leakage value of the plants were lower than 50% demonstrating that they could be applied stably to the roof installed in Korea during the winter with the lowest temperature of $-13.5^{\circ}C$.

A Preliminary Study on UAV Photogrammetry for the Hyanho Coast Near the Military Reservation Zone, Eastern Coast of Korea (동해안 군사시설보호구역 주변 향호 연안역을 대상으로 무인항공사진측량에 관한 예비 연구)

  • Kim, Baeck-Oon;Yun, Kong-Hyun;Chang, Tae-Soo;Bahk, Jang-Jun;Kim, Seong-Pil
    • Ocean and Polar Research
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    • v.39 no.2
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    • pp.159-168
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    • 2017
  • To evaluate the accuracy of UAV photogrammetry for Hyangho coast, eastern coast of Korea, we conducted a field experiment wherein UAV photogrammetry test was repeated three times. Since the Haygho coast is located within a military reservation zone, it was necessary to obtain permission to gain access to the beach and to have sensitive aerial photographs showing military facilities inspected and cropped. The standard deviation of the UAV shooting position between the three tests was less than 1 m, but repeatability of footprint on the ground was low due to wind-driven variability of the UAV pose. Self-calibrating bundle adjustment(SCBA) of implementing non-metric camera calibration was failed in one test. In two tests, the vertical error was twice as large as the pixel size except for those areas that were subject to security inspection and cropping. Given the problems that can arise with regard to the repeatability of the shooting area as well as the possibility of failure with regard to SCBA, we strongly recommend that UAV photogrammetry in coastal areas needs to be repeated at least twice.

The Design/Analysis of High Resolution LEO EO Satellite STM (지구저궤도 고정밀 관측위성 구조 및 열 개발모델 설계/해석)

  • Kim, Jin-Hee;Kim, Kyung-Won;Lee, Ju-Hun;Jin, Ik-Min;Youn, Kil-Won
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.8
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    • pp.99-104
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    • 2005
  • The major role of a spacecraft structure is to keep and support the spacecraft safely in all the launch environment, on-orbit condition and during ground-transportation and handling. In a satellite development, a structural and thermal model (STM) is developed for two goals ; demonstration of a structural and a thermal stability. In the structure point of view, STM is used to verify the static/dynamic characteristics of structure in the initial stage of development. In this paper, the structure design/analysis of high resolution LEO earth observation satellite STM is described. Also, a low level sine vibration test is performed and compared to the results of finite element analysis.

Surfactant Aided Air-sparging for Groundwater Remediation (계면촬성제 첨가에 따른 지하수 폭기법의 폭기효율 변화 연구)

  • 소효은;최경민;이승재;김헌기
    • Economic and Environmental Geology
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    • v.35 no.5
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    • pp.421-428
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    • 2002
  • Lab-scale experiments were conducted to evaluate the effect of surface tension reduction on the extension of the influence zone and the VOC removal efficiency of ground water sparging. A glass column packed with coarse sand was used for VOC removal test at two different surface tensions. A glass column without porous media was also used fer control purpose prior to sand-packed column test. A quasi-two-dimensional glass box model, packed with a sand, was used fer sparging zone tests at different water surface tensions. Surface tension of the aquoues solution used in this study was controlled using sodium dodecyl sulfate (SDS). For the glass, sand column experiments, total amount of air filled in the media increased as surface tension decreased. Toluene (used as VOC in this study) removal rate increased slightly with decreased surface tension f3r both free water column and sand-packed column. Air sparging zone extended up to 500% as the surface tension decreased. Combining the results from two different experiments, VOC removal efficiency is expected to increase significantly with surface tension reduction.