• Title/Summary/Keyword: 안정계수

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Comparison of Stability Coefficients of Radial Shape Armor Blocks Depending on Placement Methods (피복 방법에 따른 방사형 소파 블록의 안정계수 비교)

  • Min, Eun-Jong;Cheon, Se-Hyeon;Suh, Kyung-Duck
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.27 no.2
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    • pp.135-141
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    • 2015
  • In this study, two different uniform placement methods are proposed for each of Tetrapod, Rakuna-IV, and Dimple armoring a rubble mound breakwater, and the corresponding stability coefficients are determined by hydraulic experiments. The Tetrapod and Rakuna-IV show similar stability coefficients regardless of the placement methods, whereas the Dimple shows somewhat different stability coefficients depending on the placement methods. It is shown that the Dimple gives the largest stability coefficient, whereas the Tatrapod gives the smallest value. The uniform placement methods of Tatrapod and Rakuna-IV give slightly larger stability coefficients than the random placement, whereas the uniform placements of Dimple give much larger stability coefficients than the random placement. However, the small void ratio of uniform placements of Dimple requires attention because the blocks would behave like single layer system blocks so that brittle failure could occur.

Experimental Investigation on the Change of Stability Coefficient of Tetrapod According to Difference in Density (비중 차이에 따른 테트라포드 안정계수 변화에 관한 실험적 연구)

  • Lee, Dal Soo;Oh, Sang-Ho;Cho, Bong Suk
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.28 no.3
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    • pp.124-131
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    • 2016
  • In this study, a physical experiment was performed to investigate the change in the stability coefficient, defined by Hudson equation, for the tetrapod of different specific densities. The experiment was carried out once (with no repetition) for a rubble mound breakwater with 1:1.5 slope. In this experiment, the stability coefficient for the high-density tetrapod was greater than that for the normal-density tetrapod. This indicates variability of the stability coefficient according to change in the density of tetrapod. Further experiments and detailed analysis are required to investigate the effect of the density on the stability coefficient of tetrapod.

The application of simplified risk assessment for tunnel (터널 리스크 평가 기법의 적용성에 대한 연구)

  • Kim, Sang-Hwan;Lee, Chung-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.9 no.1
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    • pp.63-74
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    • 2007
  • Unexpected ground conditions have always been a major problem for the construction of tunnel. Therefore, it is necessary to evaluate the risk capacity before and/or during construction of new tunnel. This paper presents the simplified risk assessment system using modified stability number (N), namely Underground Risk Index (URI) system, to evaluate the tunnel risk possibility in the design stage. URI is a scoring system for risk possibility by rating the each appraisal elements. The modified stability number (N) which is one of risk factor in the Interaction Matrix parameters such as RQD, UCS, weathering, overburden, stability number, ground water-table, RMR, permeability and so on, is used in the system. In addition, the case study is performed in order to verify the applicability of URI-system in practice.

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Stability Number of Additionally Placed Armor Unit (Tetrapod) Covered on Existing Two-Layered Tetrapod Rubble Mound Structures: Pattern Placing Condition (기존 2층 피복 테트라포드 상부에 추가 거치되는 피복재(테트라포드)의 안정계수: 정적거치 조건)

  • Kim, Young-Taek;Lee, Jong-In
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.32 no.6
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    • pp.516-523
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    • 2020
  • Since the aging of coastal structures have been increased, the researches about the reinforcements of the existing aged structures are needed. Especially, the existing armor units placed on rubble mound structures should satisfy the stability against the increased design wave conditions. However the researches about these design problems have not been performed. In this study, the hydraulic model tests to investigate the stability number about the additionally placed armor unit were conducted. The main armor unit is a Tetrapod. The test results showed that the stability number (Kd) for additionally placed armor units(Tetrapod) increased up to maximum 10% comparing with that for 2 layers tetrapod (Kd = 8) within these test conditions with the pattern placing for existing armor layers and the stable armor layer slope for the non overtopping condition.

피복블록 형상에 따른 사면상 양압력에 관한 실험적 연구

  • 최한규;박양호
    • 어항어장
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    • pp.67-75
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    • 1998
  • 본 연구의 목적은 서로 다른 형태를 갖는 피복블록의 형상에 따른 Hudson식의 안정계수 값들과 양압력의 관계를 방파제의 안정성과 연계 해석하여, 방파제 단면설계에 있어서 피복블록의 선택 및 소요중량 산정에 효과적으로 이용하고자 한다.

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Seismic P-$\Delta$ Effects of Slender RC Columns in Earthquake Analysis (지진하중을 받는 철근콘크리트 장주의 P-$\Delta$ 효과)

  • Kwak, Hyo-Gyoung;Kim, Jin-Kook
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.19 no.4
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    • pp.375-387
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    • 2006
  • Different from the previous studies which investigated seismic P-$\Delta$ effect in slender columns though comparison of response spectra according to stability coefficients obtained from the analyses based on the assumed moment-curvature relationship, the axial force and P-$\Delta$ effect in RC columns are investigated on the basis of the layered section method which can effectively consider the changes of stiffness and yield strength due to the application of axial force in RC members. Practical ranges of slenderness and stability coefficient are assumed, and sixty sets of horizontal/vertical earthquake inputs are used in the analysis. From the parametric study, it is noted that the maximum deformation of the slender RC column is hardly affected by P-$\Delta$ effect or vortical earthquake but dominantly affected by the applied axial force. Therefore, it can be concluded that no additional consideration for the P-$\Delta$ effect and vortical earthquake is required in the seismic design of a slender RC column if the axial force effect is taken into account in the analysis and design procedures.

Stability Formula for Rakuna-IV Armoring Rubble-Mound Breakwater (사석방파제 위에 피복한 Rakuna-IV의 안정공식)

  • Suh, Kyung-Duck;Lee, Tae Hoon;Matsushita, Hiroshi;Nam, Hong Ki
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.25 no.4
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    • pp.181-190
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    • 2013
  • In this study, a total of 51 cases of hydraulic model tests has been conducted for various wave conditions and slope angles of breakwater to develop a stability formula for Rakuna-IV armoring a rubble-mound breakwater. The stability number of the formula is expressed as a function of relative damage, number of waves, structural slope, and surf similarity parameter. The stability formula is derived separately for plunging and surging waves, the greater of which is used. The transitional surf similarity parameter from plunging waves to surging waves is also presented. Lastly, to explain the stability of Rakuna-IV to the engineers who are familiar with the stability coefficient in the Hudson formula, the required weight of Rakuna-IV is calculated for varying significant wave height for typical plunging and surging wave conditions, which is then compared with those of the Hudson formula using several different stability coefficients.

Proposal of a New Experimental Method for Evaluating the Stability of Armor Blocks (소파블록의 안정성 평가에 대한 새로운 실험방법 제안)

  • Kim, Shinwoong;Lee, Seong-Dae;Lee, Kwang-Ho
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.33 no.3
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    • pp.131-138
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    • 2021
  • The armor blocks are used to protect the body of the structure and dissipate wave energies, so it is crucial to evaluate the stability of the armor unit. The stability of armor blocks has been mainly evaluated through empirical coefficients called the stability coefficient obtained from hydraulic model experiments. In this study, a new type of single-layered armor block called K-Block was proposed, and a new experimental method based on the pull-out force was proposed to evaluate the stability of the armor unit, including the interlocking effects. The pull-out force test proposed in this study directly measures the force required to separate the armor unit from the armored layer on the slope by applying a tensile force in the vertical and horizontal directions to the installed armor unit. The proposed experimental method confirmed that the interlocking effects of the armor block could be quantitatively evaluated, and the high stability of the K-Block was verified.

Experiments for Amour Stability of Low Crested Structure covered by Tripod Block (저 마루높이 구조물의 피복재 안정성 실험: Tripod 피복 조건)

  • Lee, Jong-In;Bae, Il Rho;Lim, Ho Seok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.40 no.1
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    • pp.43-49
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    • 2020
  • In this study, the stability of the low crested structure armoured by Tripod block has been investigated using two-dimensional hydraulic model tests. The effect of wave steepness and freeboard on the rock stability on crest, front, and the rear slope has been investigated. From the experimental data, the new empirical formula for the stability coefficients of the Tripod block was proposed. But Tripod is not proper to use the armour block of the low crested structure because the uplift force of this block is greater than that of Tetrapod and rock.

Experiments for Amour Stability of Low Crested Structure Covered by Rocks (저 마루높이 구조물의 피복재 안정성 실험: 피복석 피복 조건)

  • Lee, Jong-In;Bae, Il Rho;Moon, Gang Il
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.40 no.1
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    • pp.35-41
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    • 2020
  • In this study, the stability of low crested structure armoured by rock has been investigated using two-dimensional hydraulic model tests. The effect of wave steepness and freeboard on the rock stability on crest, front, and the rear slope has been investigated. Rocks were mostly damaged near the upper part of the seaward slope and the crest of the seaward side. From the experimental data, the new empirical formula for the stability coefficients of the rocks was proposed.