• Title/Summary/Keyword: Poor ground

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Study of Determination of Allowable Residual Settlement of Concrete Track Roadbed for High-Speed Railway (콘크리트궤도 토공노반의 허용잔류침하량 결정에 관한 연구)

  • Lee, Il-Wha;Yang, Shin-Chu;Jang, Seung-Yup
    • Proceedings of the KSR Conference
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    • 2007.11a
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    • pp.1121-1125
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    • 2007
  • An active application of concrete track is being expected for the future construction of Korean railroad. For the successful concrete track construction and design in earthwork areas, the residual settlement should be reasonably estimated using the proper method. The concrete track is extremely vulnerable to the damage of residual settlement. However, at the transition areas such as bridge approach, differential settlement will likely occur due to difference of stiffness, poor drainage and poor ground treatment. The maintenance is very difficult for excessive settlement on existing line, it is need to constrain the residual settlement in step of design. In this paper, it is performed the determination of the allowable residual settlement through various study to understand the residual settlement behavior of concrete track roadbed.

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Tree-Ring Growth Characteristics of Pinus thunbergii Parl. after Replanting on the Reclaimed Land from the Sea in Gwangyang Bay (광양만 임해매립지의 곰솔 이식 이후의 연륜생장 특성)

  • 김도균;박원규;서정욱
    • Korean Journal of Environment and Ecology
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    • v.16 no.1
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    • pp.1-9
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    • 2002
  • This study was carried out to examine the tree-ring growth characteristics of Pinus thunbergii Parl. after replanting on the reclaimed land from the sea in Kwangyang bay, The factors, mostly affecting the growths of Pinus thunbergii Parl. , were the replanting stress and drought. The growth reduction due to replanting occurred in the replanting year and following year, but that due to drought after 2-3 years of replanting. The growth recovery after replanting differed with soil condition. The sites showing fast recovery were the covered ground of improve soil, the ground of medium mounding, the top and the slope ground of big mounding sites. The filled ground of improve soil and the lower ground of big mounding sites showed retarded growths. The mean sensitivity(year-to-year variation) and the coefficient of variation(tree-to-tree variation in a certain year) in tree rings of Pinus thunbergii Parl. were higher in the poor soil sites than in the favourable soil ones. The physical characteristics of the soil, especially soil hardness, were the most crucial. The mean sensitivity and the coefficient of variation were also low in the salty soil environment.

A Case Study of Ground Subsidence in a Groundwater-saturated Limestone Mine (지하수로 포화된 석회석광산의 지반침하 사례연구)

  • Choi, Woo-Seok;Kim, Eun-Sup;Kang, Byung-Chun;Shin, Dong-Choon;Kim, Soo-Lo;Baek, Seung-Han
    • The Journal of Engineering Geology
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    • v.25 no.4
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    • pp.511-524
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    • 2015
  • Groundwater causing subsidence in limestone mines is uncommon, and thus relatively poorly investigated. This case study investigated the cause and possibility of future subsidence through an evaluation of ground stability at the Samsung limestone mine, Chungcheongbuk-do. The ground near the mine area was evaluated as unstable due to rainfall permeation, and subsidence in the unmined area resulted from groundwater level drawdown. Future subsidence might occur through the diffusion of subsidence resulting from the small thickness of the mined rock roof, fracture rock joints, and poor ground conditions around the mine. In addition, the risk of additional subsidence by limestone sinkage in corrosion cavities, groundwater level drawdown due to artificial pumping, and rainfall permeation in the limestone zone necessitates reinforcements and other preventative measures.

Deformation Behavior and Reinforcement Design of a Tunnel Excavated in Weak Rock by the NATM (연약암반에 굴착되는 NATM 터널의 변형거동과 보강설계)

  • 서영호;이정인
    • Tunnel and Underground Space
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    • v.3 no.2
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    • pp.132-141
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    • 1993
  • Laboratory and field tests were performed to find out the effectiveness of ground improvement by grouting for an urban subway tunnel that was excavated in weak rock by the NATM. Field measurements were carried out to monitor the behavior of rock mass around the tunnel and to ensure the validity of the current design of the distance form the measuring points to the tunnel face. The final converged displacement and the peroid were predicted using the gamma function. It was found that the ground improvement in terms of reduced permeability and increased stength in the self-supportability of the excavation face enabled the NATM applied in poor gorund. As the result of applying the gamma function to the predicting of displacement, the final displacement including the preceding one and the converged period could be approximately predicted at the early excavation stage.

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Dutile Regime Parallel Grinding of BK7 (BK7의 평행축 연성모드 연삭가공)

  • Lee, Hyeon-Sung;Kim, Min-Jae;Koo, Hal-Bon;Hwang, Yeon;Kim, Hye-Jeong;Kim, Jeong-Ho
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.1
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    • pp.85-89
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    • 2012
  • Conventional grinding of BK7 glass will normally result in brittle fracture at the surface, generating severe sub-surface damage and poor surface finish. The precision grinding of BK7 glass in parallel grinding modes has been investigated. Grinding process, maximum chip thickness, ductile/brittle regime, surface roughness and sub-surface damage have been addressed. Special attention has been given to the condition for generating a ductile mode response on the ground surface. Experiments reveal that the level of surface roughness and depth of sub-surface damage vary differently for different condition. This study gives an indication of the strategy to follow to achieve high quality ground surfaces on brittle materials.

Mobile Crane Ground-Fixing System (이동식 크레인의 접지설계 시스템)

  • Ho, Jong-Kwan;Seo, Jong-Min;Kim, Sun-Kuk
    • KIEAE Journal
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    • v.7 no.6
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    • pp.83-90
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    • 2007
  • A mobile crane has been more frequently used to deal with the increased capital-intensive projects in line with the economic growth, but the operation is still heavily dependent on personal experience in the past, resulting in severe overturn accidents that cause the loss of lives and damage to the properties. A crane shall be installed in a systematic manner that proved to be safe in engineering aspect, and should the installation and operation be blindly dependent on experience alone, it would apparently cause a great risk. Particularly the mobile crane, among others, frequently causes a severe overturn accident due to poor ground-fixing device. The study therefore focused on fixing system of mobile crane and the outcome is highly expected to make a great commitment to selecting the optimal type of crane for the project as well as to securing the safety during construction.

Stability Evaluation for a riverbed tunnel in the Han River at the Fault Zone Crossing (한강 단층대를 통과하는 하저터널의 안정성 확보에 관한 연구)

  • Woo, Jong-Tae;Lee, Song
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.3
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    • pp.225-231
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    • 2001
  • When building tunnels beneath riverbeds where very large quantities of groundwater inflow exist, added to high water head the soil supporting conditions are very poor because the soil consists of sand and silt, etc. It is necessary to have grouting and mini pipe roof installed in the region for ground reinforcement to decrease permeability. According to this result of horizontal boring and laboratory soil testing, ground reinforcement was achieved by L.W grouting for range of 3.0 times the tunnel radius, to increase stability of the tunnel we used the ling-cut method, 0.8m for one step excavation, shotcrete with 25cm thick, steel lib with H-$125{\times}125$. and a temporary shotcrete invert 20cm thick was installed to prevent deformation of the tunnel.

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Study on the Frost Damage of Self-Compacting Concrete in Cold Weather Regions (한랭지에 있어서 고류동콘크리트의 동해에 관한 연구)

  • ;;;;Miura, Takashi
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.763-766
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    • 1999
  • The objective of this study was to investigate the influence of low temperature curing on resistance of freezing and thawing of self-compacting concrete placed in cold weather regions. The experimental study results indicated that the self-compacting concrete incorporating ground granulated blast-furnace slag showed good resistance to freezing and thawing, and the self-compacting concrete cellulose viscous agent had relatively poor resistance to freezing and thawing.

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A Case Study on the Improvement of Rail Road Subgrade using Super Injection Grouting Method - Strength Increase in Marine Clay - (철도노반개량을 위한 고압분사 사례연구 - 해성점토지반에서의 강도증대효과를 중심으로-)

  • 천병식;최현석
    • Proceedings of the KSR Conference
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    • 1998.11a
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    • pp.103-110
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    • 1998
  • Several soil improvement methods are applied to stabilize soft ground. But their improvement effects are known to be reduced in view of strength under poor conditions such as marine clay. The purpose of this paper is to investigate the strength increase effects of super injection grouting on the marine clay, A series of laboratory tests and chemical analysis tests has been peformed. Through this study, the causes of strength inferiority of treated soil was analyzed and soil improvement effects of grouted soil was presented.

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Analysis of Influence Parameters to Evaluate the Effective Depth of Improvement of Dynamic Compaction Method (동다짐 공법의 유효다짐깊이 결정에 영향을 주는 인자 분석)

  • Kim, Hong-Taek;Lee, Hyuk-Jin;Park, Inn-Joon
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.659-666
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    • 2004
  • Dynamic compaction has evolved as an acceptable method of site improvement by treating poor soils in situ. The method is often an economical alternative for utilizing shallow foundations and preparing subgrades for construction when compared with conventional solutions. In general, the installation purpose of dynamic compaction are to increase bearing capacity and decrease differential settlement within a specified depth of improvement. This method involves the s systematically dropping large weights onto the ground surface to compact the underlying ground. The weights used on dynamic compaction projects have been typically constructed of steel plates, sand or concrete filled steel shells, and reinforced concrete. Typically, weights range from 5-20 ton and base configurations are, circular or octagonal. In this study, the effective depth of improvement is evaluated based on the numerical analysis code, the dynamic analysis of FLAC-3D program, in order to analyze the influence parameters ; ground conditions, maximum applied load and the area of compaction plate.

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