• Title, Summary, Keyword: 강화노반

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Determination on the Reinforced Roadbed Thickness of Concrete Track at Embankment Section (흙쌓기 구간에서 콘크리트궤도 강화노반의 두께 결정에 관한 연구)

  • Lee, Il-Wha;Lee, Sung-Jin;Sin, Min-Ho;Hwang, Sun-Kun;Lee, Chang-Jin
    • Journal of the Korean Society for Railway
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    • v.12 no.6
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    • pp.835-843
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    • 2009
  • Recently the more stable roadbed is required due to the high speed and design load. Therefore the reinforced roadbed was introduced as the solution. But the thickness and stiffness of reinforced roadbed in design code is being conservatively assessed by the foreign code without considering the domestic construction condition. In this paper, adequate Young's modulus, drain capacity, freezing depth, economical efficiency, bearing capacity, construction condition and 3-D finite element method were employed to determine the proper thickness of reinforced roadbed at the embankment section.

Evaluation on the Applicability of the Conventional Roadbed Stiffness for High Speed Concrete Track (일반철도 노반 강성조건에서의 고속철도용 콘크리트 궤도의 적용성 검토)

  • Lee, Jin Wook;Lee, Seong Hyeok;SaGong, Myung;Lyu, Tae Jin
    • Journal of the Korean Society for Railway
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    • v.16 no.1
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    • pp.40-46
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    • 2013
  • Based on Korean railway design standards, the thicknesses of the reinforced roadbeds of conventional and high speed railways are different, and so too, for the size distribution of the ballast particles. Accordingly, considerable cost would be required to increase operating speeds of conventional lines, in particular related to changing from a ballasted track system to a ballastless one. In this study, applicability of a roadbed which supports conventional ballasted track, for use as a ballastless track for a high speed rail line was examined. A reinforced roadbed for a conventional railway is 20cm thick, and the type of material used for a conventional reinforced roadbed is M-40 (crushed gravel for road embankments). A dynamics test was conducted to evaluate the occurrence of the permanent settlement of the track substructure. These results suggest that, without changes to the track substructure, an operational speed of 400km/h is feasible with a ballastless track. This result; however, is from laboratory experiments. Further studies, such as numerical analyses or field validation, are required.

Resilient Moduli of Sub-ballast and Subgrade Materials (강화노반 및 궤도하부노반 재료의 회복탄성계수)

  • Park, Chul-Soo;Choi, Chan-Yong;Choi, Choong-Lak;Mok, Young-Jin
    • Journal of the Korean Society for Railway
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    • v.11 no.1
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    • pp.54-60
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    • 2008
  • In the trackbed design using elastic multilayer model, the stress-dependent resilient modulus $(E_R)$ is an important input parameter, that is, reflects substructure performance under repeated traffic loading. However, the evaluation method for resilient modulus using repeated loading triaxial test is not fully developed for practical purpose, because of costly equipment and the significantly fluctuated values depending on the testing equipment and laboratory personnel. The this study, the paper will present an indirect method to estimate the resilient modulus using dynamic properties. The resilient modulus of crushed stone, which is the typical material of sub-ballast, was calculated with the measured dynamic properties and the range of stress level of the sub-ballast, and approximated with the power model combined with bulk and deviatoric stresses. The resilient modulus of coarse grained material decreases with increasing deviatoric stress at a confining pressure, and increases with increasing bulk stress. Sandy soil (SM classified from Unified Soil Classification System) of subgrade was also evaluated and best fitted with the power model of deviatoric stress only.

Settlement Characteristics of the Reinforced Railroad Roadbed with Crushed Stones Under a Simulated Train Loading (모사 열차하중 재하에 따른 쇄석강화노반의 침하특성)

  • Hwang, Seon-Keun
    • Journal of the Korean Geotechnical Society
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    • v.20 no.2
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    • pp.5-13
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    • 2004
  • Conventional railroad roadbeds constructed with soils can easily deteriorate with time due to the increase of repeated traffic loading, increase of train speed, built-up of ground water on the roadbed and decrease of permeability in the roadbed layer, etc. In this study, performance of reinforced railroad roadbeds with the crushed stones was investigated through the real scale roadbed tests and numerical analysis. It was found that the reinforced roadbed with crushed stone had less elastic and plastic vertical displacement(settlement) than general soil roadbed regardless of the number of loading cycles. It was also found through the actual testing that for the roadbed with the same thickness, the displacement of reinforced roadbed decreases with the increase of subgrade reaction modulus. The settlement of reinforced roadbed with the same subgrade reaction modulus also decreases with the increase of thickness of the reinforced roadbed. However, the subgrade reaction modulus is a more important factor to the total plastic displacement of the track than the thickness of the crushed stone roadbed.

Evaluation of Resilient Modulus for Reinforced Trackbed using Large Triaxial Tests (대형삼축압축시험을 이용한 강화노반재료의 회복탄성계수 평가)

  • Lee, Sung Jin;Lee, Jin Wook;Lee, Seong Hyeok;Sagong, Myung
    • Journal of the Korean Society for Railway
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    • v.17 no.6
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    • pp.415-422
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    • 2014
  • Reinforced trackbeds are an important layer that has a significant effect on the deformation of the track, therefore, a deeper understanding of reinforced trackbeds is necessary. In this paper, we conduct a large triaxial test in order to evaluate the resilient modulus ($M_R$) of reinforced trackbed materials through considering several factors such as the grain size distribution (GSD) and loading conditions. It is identified that the maximum size of the particle, GSD, and compacted water content affect the $M_R$ but the loading frequency does not. Because these tests are performed with consideration of the field environment, the test results are useful for analyzing tracks including reinforced trackbeds. The data are limited to evaluating the parameters of $M_R$ model; however the parameters of the deviatoric and bulk stress models that can be used in various loading conditions are proposed.

Development of Permanent Deformation Prediction Model for Trackbed Foundation Materials based on Shear Strength Parameters (강화노반 쇄석재료의 전단강도특성을 고려한 영구변형예측모델 개발)

  • Lim, Yujin;Hwang, Jungkyu;Cho, Hojin
    • Journal of the Korean Society for Railway
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    • v.15 no.6
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    • pp.623-630
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    • 2012
  • Formation used as trackbed foundation for providing vertical bearing capacity onto rail foundation are composed of crushed stones usually with certain type of grain size distribution. Permanent deformation in trackbed foundation can be generated by increasing number of load repetition due to train traffic increases, causing track irregularity. In this study, a specially prepared trackbed foundation materials (M-40) used in Korea has been tested using a large repetitive triaxial compression apparatus in order to understand resilient and permanent deformation characteristics of the material. From these test results, resilient and permanent deformation characteristic are analyzed so that a permanent deformation model is developed which can consider number of load repetition N, confining stress (${\sigma}_3$), shear stress ratio(${\tau}/{\tau}_f$) and stiffness of the material.

Characteristics of Displacement of the Reinforced Roadbed Materials with Cyclic Loading (동적하중 재하시 강화노반 재료별 침하 특성)

  • 황선근;이성혁;최찬용
    • Journal of the Korean Society for Railway
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    • v.5 no.2
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    • pp.70-76
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    • 2002
  • In this study, performance of reinforced railroad roadbeds with the reinforced roadbed materials were investigated through the real scale roadbed tests. It was also found that the reinforced roadbed with reinforced roadbed materials has less elastic and plastic settlement than the one with soil. The slag roadbed was more effective than the crushed stone roadbed with the same condition for load distribution. Therefore considering overall characteristics of reinforced roadbed material, the optimum thickness was recommended as 50 cm. Furthermore the real scale model test under the simulated rainfall condition, the settlement in the slag roadbed was about 8 times smaller than the settlement in the soil roadbed.

Laboratory Test for Permanent Settlement Behavior of Geo-materials used in Railway Considering Grain size distribution and Water content (입도 및 함수비 조건에 따른 철도 노반 재료의 영구침하거동 요소시험평가)

  • Lee, Sung Jin;Lee, Il Wha;Lee, Su Hyung;Eum, Ki Young
    • Journal of the Korean Society for Railway
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    • v.18 no.4
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    • pp.354-362
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    • 2015
  • Since allowable settlement of concrete slab track is about 30mm, a lot of attention must be paid to the settlement of the earthwork (reinforced trackbed, upper subgrade, under subgrade) under the concrete track. To this end, more experimental data should be accumulated through tests for these materials. In this study, we evaluate the long-term settlement of reinforced trackbed and subgrade materials using factors such as repeated loading conditions, water content, and grain size distributions in a large triaxial test and a large oedometer test. In cases in which the performance of the reinforced trackbed layer meets the design criteria, the settlement caused by train load was considerably small. But, when the water content increases in the subgrade, unexpectedly large settlement might occur for certain grain size distributions of the subgrade materials.

A Study on Basic Properties of the Reinforced-roadbed Material Using Water Quenched Blast Furnace Slag (수재슬래그를 이용한 강화노반재료의 기초적 특성 연구)

  • 이선복;윤지선
    • Journal of the Korean Geotechnical Society
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    • v.19 no.1
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    • pp.103-110
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    • 2003
  • The development of reinforced-roadbed material in substitute for existing roadbed is necessary to protect its failure from the dynamic stress and vibration caused by the traveling of the high-speed and heavy trains. The water quenched blast furnace slag having potential hydraulic reactivity is one of the materials in substitute for soil reinforced-roadbed. We carried out the study of basic properties of roadbed material using Portland cement and CSA(calcium sulphoaluminate) as the activator for the evaluation of its application. As the result of the strength test, this material satisfied design criterion for reinforced-roadbed. Optimum mixing ratio of this reinforced-roadbed material was 15 ~ 17.5 percent of cement and 2.5 percent of CSA by weight of the blast furnace slag. Especially, as permeability is above $10^{-3}$cm/sec, this material proved to have functions of both reinforced roadbed and drainage layer.

Optimal Section of Ballasted Asphalt Track Considering Design Lifetime and Economic Feasibility (설계수명 및 경제성을 고려한 유도상 아스팔트 궤도의 최적 단면 산정)

  • Lee, Seonghyeok;Lee, Jinwook;Lee, Hyunmin
    • Journal of the Korean Society for Railway
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    • v.18 no.3
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    • pp.241-251
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    • 2015
  • Compared with ballasted track (BT), ballasted asphalt track (BAT) has been increasingly adopted in many countries due to its more greatly reduced reinforced roadbed thickness and smaller cumulative plastic deformation, and its advantages in terms of maintenance. In this respect, the authors' previous research includes analysis of BAT sections that show performance similar to that of BT sections of the present specifications; reliability verification of the analysis results through real-sized static and dynamic train-load tests were performed. Based on previous research, this paper estimates the track lifetime using the strain of the lower roadbed according to reinforced roadbed thickness; using probabilistic LCC analysis, this paper presents a BAT section that satisfies the design lifetime and that has performance similar to or higher than that of BT.