• Title/Summary/Keyword: Ground-Reflect Effect

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The Stability Analysis of Near Parallel Tunnels Pillar at Multi-layered Soil with Shallow Depth by Numerical Analysis (수치해석에 의한 저토피 다층지반에서 근접 병설터널 필라의 안정성 분석)

  • Lim, Hyungmin;Son, Kwangrok
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.1
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    • pp.53-62
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    • 2014
  • In Korea, in general, separation distance between existing parallel tunnels was set at two to five times as distant as the diameter of the tunnels according to ground conditions. Recently, however, actual applicability of closely spaced parallel tunnels whose distance between tunnel centers was shorter than the diameter has increased due to environmental damages resulting from massive cutting, restriction in purchase of required land, and maintenance of linear continuity. In particular, when the pillar width of tunnel decreases, the safety of pillars affects behaviors of the tunnel and therefore the need for diverse relevant studies has emerged. However, research so far has been largely confined to analysis of behavior characteristics of pillars, or parameters affecting design, and actually applicable and quantitative data have not been presented. Accordingly, in order to present a stability evaluation method which may maximally reflect construction conditions of spots, this study reflected topographical and stratigraphic characteristics of the portal part with the highest closeness between the tunnels, simulated multi-layer conditions with rock mass and complete weathering, and assessed the degree of effect the stability of pillars had on the entire tunnels through numerical analysis according to changes in pillar width by ground strength. This study also presented composite analysis result on ground surface settlement rates, interference volume rates, and average strength to stress and a formula, which may be applicable to actual work, to evaluate safety rates of closely spaced parallel tunnel pillars and minimum pillar width by ground strength based on failure criteria by Hoek-Brown (1980).

Quasi 1D Nonequilibrium Analysis and Validation for Hypersonic Nozzle Design of Shock Tunnel (충격파 풍동의 극초음속 노즐 설계를 위한 Quasi 1D 비평형 해석 및 검증)

  • Kim, Seihwan;Lee, Hyoung Jin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.8
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    • pp.652-661
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    • 2018
  • It is necessary to resolve the absolute velocity as well as Mach number to reflect the high temperature effect in high speed flow. So this region is classified as high enthalpy flows distinguished from high speed flows. Many facilities, such as arc-jet, shock tunnel, etc. has been used to obtain the high enthalpy flows at the ground level. However, it is difficult to define the exact test condition in this type of facilities, because some chemical reactions and energy transfer take place during the experiments. In the present study, a quasi 1D code considering the thermochemical non-equilibrium effect is developed to effectively estimate the test condition of a shock tunnel. Results show that the code gives reasonable solution compared with the results from the known experiments and 2D axisymmetric simulations.

Effect of Concentrate Level on the Formation of Conjugated Linoleic Acid and Trans-octadecenoic Acid by Ruminal Bacteria when Incubated with Oilseeds In Vitro

  • Wang, J.H.;Song, M.K.;Son, Y.S.;Chang, M.B.
    • Asian-Australasian Journal of Animal Sciences
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    • v.15 no.5
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    • pp.687-694
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    • 2002
  • An in vitro study was conducted to examine the effect of addition level of concentrate on fermentation characteristics and long-chain unsaturated fatty acids composition, especially conjugated linoleic acid (CLA) and trans-octadecenoic acid (t-FA) by mixed ruminal bacteria when incubated with linseed or rapeseed. Four levels (0.83, 1.25, 1.67 and 2.08%, w/v) of concentrate and ground oilseeds (linseed or rapeseed; 0.83%, w/v) were added to mixed solution of strained rumen fluid with artificial saliva (1:1, v/v) in the glass jar with a glass lid equipped with stirrer, and was incubated anaerobically for 24 h at $39^{\circ}C$. Addition level of concentrate slightly reflect on pH and ammonia concentration of the culture solution at the various incubation times when incubated with both linseed and rapeseed. Total VFA concentration slightly increased with incubation times and concentrate levels for incubations with oilseeds. While CLA composition had a clearly increasing trend with incubation time when incubated with linseed, percent CLA was relatively stable when incubated with rapeseed. Percent CLA, however, had a clearly decreasing trend with concentrate level throughout incubation times with significances at 3 h incubations when incubated with linseed (p<0.038) and rapeseed (p<0.0009). The differences in compositions of t-FA were relatively small among concentrate levels for both incubations with linseed and rapeseed. The ratios of t-FA to CLA were lower for linseed with increased proportion of CLA than for rapeseed.

Relation between Cone Tip Resistance and Deformation Modulus of Cemented Sand (고결모래의 콘선단저항과 변형계수의 관계)

  • Lee, Moon-Joo;Choi, Sung-Kun;Choo, Hyun-Wook;Lee, Woo-Jin
    • Journal of the Korean Geotechnical Society
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    • v.24 no.12
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    • pp.53-63
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    • 2008
  • In this study, the cone tip resistances of cemented sand are measured by performing a series of miniature cone penetration tests in large calibration chamber, and the relations with constrained modulus, unconfined compressive strength, and shear strength of cemented sand are suggested. Experimental results show that both the cone tip resistance and constrained modulus of sand increase with increasing cementation effect as well as relative density and confining stress. However, it is observed that the relative density and confining stress have more significant influence on cone tip resistance than constrained modulus of cemented sand. Since the cone penetration into the ground induces the damage of cementation, the cone tip resistance can't properly reflect the cementation effect of sand. An analysis based on the constrained modulus shows that the measured cone tip resistance underestimates the deformation modulus of cemented sand by about $70{\sim}85%$. In addition, this study establishes various relationships among the above soil properties from the regression analysis.

A numerical study on the characteristics of small underground cavities in the surrounding old water supply and sewer pipeline (노후 상하수관 주변지반의 소규모 지하공동 형상 특성을 고려한 수치해석에 관한 연구)

  • An, Joon-Sang;Kang, Kyung-Nam;Song, Ki-Il;Kim, Byung-Chan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.2
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    • pp.287-303
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    • 2018
  • In recent years, the occurrence of ground subsidence phenomenon is frequent in Korea. The Korean government has enacted a special law on underground safety and the law will be enforced from January 1, 2018. Under this new law, underground excavation should be assessed for underground safety impacts. After excavation construction, periodic geophysical surveys should be conducted to investigate the occurrence of underground cavities. When underground cavities were discovered, the underground safety was assessed through numerical analysis. However, it is controversial because the method of numerical modeling the discovered underground cavity is due to be established. In this study, the effect of the depth of the underground cavity from the shape of the underground cavity to the underground cavity was studied using a continuum analysis program. In this study, a method to reflect the shape of the underground cavity to the numerical modeling is presented. The relationship between the shape and depth of the underground cavity, and the factor of safety calculated by the shear strength reduction method (SSR) is presented. The results of this study are expected to form the basic data on underground safety impact assessment.

Fault rupture directivity of Odaesan Earthquake (M=4.8, '07. 1. 20) (오대산지진(M=4.8, '07. 1. 20)의 단층파열방향성)

  • Yun, Kwan-Hee
    • Geophysics and Geophysical Exploration
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    • v.11 no.2
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    • pp.137-147
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    • 2008
  • Fault rupture directivity of the Odaesan earthquake, which was inferred to be the main cause of the high PGAvalue (> 0.1 g) unusually observed at the near-source region, was analyzed by using the data from the nearby (R < 100 km) dense seismic stations. The Boatwright's method (2007) was adopted for this purpose in which the azimuth and takeoff angle of the unilateral rupture directivity function could be estimated based on the relative peak ground-motions of seismic stations resulting from the nature of the rupture directivity. In this study, the approximate values of the relative peak ground-motions was derived from the difference between the log residuals of the point-source spectral model (Boore, 2003) for the main and secondary events based on the Random Vibration Theory. In this derivation, the spectral difference for a frequency range between the source corner frequencies of main and secondary events was considered to reflect only the effect of the fault directivity. The inversion result of the model parameters for the fault directivity function showed that the fault-plane of NWW-SEE direction dipping steeply to the North with high rupture velocity near upward in SE direction is responsible for the observed high level of ground-motion at the near-source region.

A Numerical Study on the Behavior of Steel Fiber Reinforced Shotcrete in Consideration of Flexural Toughness (휨인성을 고려한 강섬유보강 숏크리트 거동의 수치해석적 연구)

  • Cho, Byoung-Ouk;You, Kwang-Ho;Kim, Su-Man;Lim, Doo-Chul;Lee, Sang-Don;Park, Yeon-Jun
    • Tunnel and Underground Space
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    • v.17 no.5
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    • pp.411-427
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    • 2007
  • Reliability in tunnel analysis is necessary to accomplish technically sound design and economical construction. For this, a thorough understanding of the construction procedure including the ground-support interaction has to be obtained. This paper describes a proper modelling technique to simulate the behavior of the steel fiber reinforced shotcrete (SFRS) which maintain the supporting capability in post-failure regime. The additional supporting effect of the steel support was also verified by 3-D analyses and a new load distribution factor were proposed. The use of the plastic moment limit (PML) alone can eliminate the occurrence of the awkwardly high tensile stress in the shotcrete and can successfully model the post-peak ductile behavior of the SFRS. But with this method, moment is limited whenever the stress caused by moment reaches tensile strength of the shotcrete irrespective of the stress by axial force. Therefore, it was necessary to find a more comprehensive method which can reflect the influence of the moment and axial force. This can be accomplished by the proper use of "liner element" which is the built-in model in FLAC. In this model, the peak and residual strength as well as the uniaxial compressive strength of the SFRS can be specified. Analyses were conducted with these two models on the 2-lane road tunnels excavated in class IV and V rock mass and results were compared with the conventional elastic beam model. Results showed that both models can reflect the fracture toughness of the SFRS which could not be accomplished by the elastic beam model.

User Experience Design of Interior Driving Sound for Electric Vehicle : Focusing on the Contextual Information and Quietness (전기자동차 실내 주행 사운드의 사용자 경험 디자인 : 맥락정보성과 정숙성을 중심으로)

  • Lee, Dahye;Shim, Hye Rin;Choi, Junho
    • The Journal of the Korea Contents Association
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    • v.16 no.2
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    • pp.14-24
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    • 2016
  • Recently, the sound design of the electric vehicle has emerged as one of the new research objects. This study was conducted to explore and examine major values of interior driving sound of the electric vehicle from the perspective of user experience. An exploratory study based on the ground theory extracted contextual information and quietness as independent variables, and then we analyzed the main and interaction effects of those two variables on the usefulness, emotion, and satisfaction through a $2{\times}2$ factorial experimental design. The experimental study demonstrated that the effect on the user experience of electric vehicle can be conditioned by the combination of contextual information sound and quietness. Based on the results of this study, we suggested future research agendas for the optimization of user needs which reflect individual preference of interior driving sound values.

Deducing environmentally conscious factors for apartment complex planning and weight evaluation (환경요소를 고려한 공동주택 단지계획요소 도출 및 가중치 평가)

  • Jung, Suk-Jin;Seo, Jung-Bum;Yoon, Seong-Hwan
    • KIEAE Journal
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    • v.16 no.6
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    • pp.51-56
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    • 2016
  • Purpose: As declines in the quality of residential environments occur, such as urban heat island effect, tropical night phenomenon, and violations of right to light and privacy due to urban densification and high rise building, these problems are emerging as social issues. In order to improve these issues, design factors which consider environmental aspects must be selected when planning apartment complexes, and ways to reflect them in the planning phase must be explored. Method: In this study, the analytical hierarchy process(AHP) was used to deduce design factors that considered environmental elements during the planning of apartment complexes. Furthermore, the priority and weight for each evaluation index were assessed. The objective was to propose a guideline for planning apartment complexes by finding the best solution for each evaluation index using complex weight values. Result: Floor area ratio was selected as the most important evaluation criterion in the environmentally conscious evaluation index for apartment complex planning. The shape and placement of skylights were selected as the most important evaluation criteria in the sunshine environment for a pleasant residential environment. Ground surface cover design was selected as the most important criterion in the outdoor thermal environment index for improving the microclimate within cities and apartment complexes. Thus, the results of this study can serve as an investigation guideline that concerns policy and regulations, and as reference data that can be used in planning apartment complexes.

Seismic Safety Assessment of Long Period Structures Base on Elastic/Inelastic Response Characteristics (장주기구조물의 탄소성응답특성을 고려한 지진안전성 평가)

  • Bang, Myung-Seok
    • Journal of the Korean Society of Safety
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    • v.26 no.3
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    • pp.52-58
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    • 2011
  • The earthquake characteristic assessment of social overhead facilities would be an important examination issue for seismic capacity enhancement. This study is intended to reasonably evaluate the structural behavior of longperiod frame structures considering near-fault and far-fault earthquake characteristics. Elastic/inelastic time history analyses were performd by selecting the objective structure which can precisely reflect the effect of input ground motion. Based on the result of numerical analysis, we have investigated response aspects of shear force, moment, acceleration and displacement according to earthquake characteristics. Moreover, in order to understand the inelastic behavior of the objective structure, we have analyzed and compared collapse modes by considering the occurrence process of plastic hinges. The outcome of this research is expected to provide the basic information for the seismic safety assessment of long-period frame structures.