• Title/Summary/Keyword: Reinforced Roadbed

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Critical Speed Analysis of Geogrid-Reinforced Rail Roadbed (지오그리드로 보강된 철도노반의 한계속도에 관한 연구)

  • 신은철;이규진;오영인
    • Proceedings of the KSR Conference
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    • 2001.10a
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    • pp.534-539
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    • 2001
  • This paper presents the critical speed analysis of geogrid-reinforced rail roadbeds on soft soil. A rail roadbed on soft ground must be designed to avoid intolerable stress in the underlying soil and to give sufficient support for the rail system. At high speeds, the deformation of rail systems will gain dynamic amplification, and reach excessive values as a certain speed, here termed critical speed is approached. The elastic Winkler foundation model was used to predict the critical speed of geogrid-reinforced rail roadbeds on soft soil and the model properties were determined by the in-situ cyclic plate load test. Based on the parametric study of elastic beam on Winkler foundation model, the critical speed increase with the increase of the flexural risidity of subgrade EI and the stiffness coefficient of Winkler foundation k. From the in-situ cyclic load tests and analysis of elastic beam on Winkler foundation model, the critical speed increase with increase in number of reinforced layer and non-dimensional value for depth of first geogrid layers and the thickness of reinforced rail roadbed u/d.

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Development of A Permanent Deformation Model based on Shear Stress Ratio for Reinforced-Roadbed Materials (전단응력비 개념에 기초한 강화노반의 영구변형 모델 수립)

  • Lim, Yu-Jin;Lee, Seong-Hyeok;Kim, Dae-Seong;Park, Mi-Yun
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.2049-2056
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    • 2011
  • The reinforced-roadbed materials composed of crushed stones are used for preventing vertical deformation and reducing impact load caused by highspeed train. Repeated load application can induce deformation in the reinforced-roadbed layer so that it causes irregularity of track. Thus it is important to understand characteristics of permanent deformation in the reinforced-subbase materials. The characteristics of permanent deformation can be simulated by prediction model that can be obtained by performing repetitive triaxial test. The prediction model of permanent deformation is a key-role in construction of design method of track. The prediction model of permanent deformation is represented in usual as the hyperbolic function with increase of number of load repetition. The prediction model is sensitive to many factors including stress level etc. so that it is important to define parameters of the model as clearly as possible. Various data obtained from repetitive triaxial test and resonant column test using the reinforced-roadbed of crushed stone are utilized to develop a new prediction model based on concept of shear-stress ratio and elastic modulus. The new prediction model of permanent deformation can be adapted for developing design method of track in the future.

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Static Behavior of Reinforced Railway Roadbed by Geotextile Bag (지오텍스타일 백으로 보강된 철도노반의 정적거동 분석)

  • Lee, Dong-Hyun;Shin, Eun-Chul
    • Journal of the Korean Society for Railway
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    • v.9 no.2 s.33
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    • pp.180-186
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    • 2006
  • In this study, a large-scale laboratory model test, 2-D and 3-D numerical analyses were conducted to verify the reinforcement effect by utilizing geotextile bag on the railway roadbed. Static loading which simulated train load was applied on the geotextile bag-reinforced railway roadbed and also unreinforced railway roadbed, Computer program named Pentagon which is a part of FEM programs was used in the numerical analysis. Based on the results of laboratory test, 2-D and 3-D numerical analyses, the effect of load distribution and settlement reduction was found to be depending on the geotextile characteristics, tensile strength of geotextite, and interface friction angle between geotextile bags. In general, the result of 2-D and 3-D numerical analyses shows lower value than that of laboratory test. Also, the result of 3-D numerical analyses shows lower value than that of 2-D numerical analyses because of its stress transfer effect.

Engineering characteristics of reinforced solidified roadbed (친환경 도로조성을 위한 보강형 고화도로노반의 공학적 특성)

  • Koh, Yong-Kook
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.906-909
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    • 2005
  • The purpose of this paper is to study on the construction of roadbed with environmental friendly soil amendment agent and reinforced fiber. The special amendment agent and fiber used in this study has a function of soil-cement-agent solidification and reinforcement. A series of laboratory experiments including unconfined compressive strength, tensile strength, compaction test were carried out to investigate the physical and mechanical characteristics of roadbed treated by solidifying agent and fiber. The results of this research showed that the roadbed using poor soil could be efficiently constructed by treatment of this amendment agent and fiber.

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Development of A Simple Design Monograph for Track Sublayers (궤도 하부구조설계를 위한 간이 설계 모노그래프 개념 개발)

  • Park, Mi-Yun;Lee, Jin-Ug;Lee, Seong-Hyeok;Park, Jae-Hak;Lim, Yu-Jin
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.428-435
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    • 2011
  • In general, thickness of the sublayers under track is designed based on concept of vertical soil reaction value or vertical stiffness. However, this design method cannot take consideration into soil-track interaction under repetitive load, traffic condition and velocity of the train. Furthermore, the reinforced roadbed soils experience complex behavior that cannot be explained by conventional stress-strain relation expressed as soil reaction value k. The reinforced roadbed soils also can produce cumulative permanent deformation under repetitive load caused by train. Therefore new design method for the sublayers under track must be developed that can consider both elastic modulus and permanent deformation. In this study, a new design concept, a rule-of-thumb, is proposed as the form of design monograph that is developed using elastic multi-layer and finite element programs by analyzing stress and deformation in the sublayers with changing the thickness and elastic modulus of the sublayers and also using data obtained from repetitive triaxial test. This new design concept can be applied to design of the reinforced roadbed before developing full version of design methodology that can consider MGT, axial load and the material properties of the layers. The new design monograph allows the user to design the thickness of the reinforced roadbed based on permanent deformation, elastic modulus and MGT.

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Static Behavior of Geotextile Container for Urgent Restoration of Rail Roadbed (철도노반 보수용 토목섬유 콘테이너의 정적 거동특성 분석)

  • Shin Eun Chul;Koh Tae Hoon;Cho In Hui;Lee Jun Chul
    • Proceedings of the KSR Conference
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    • 2003.10b
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    • pp.79-84
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    • 2003
  • Utilizing of the geotextile container shows several advantages such as standardized construction, factory manufactured products, the control of quality, workability, and economical point of view. Recently this technique can be applied to rehabilitate the loss of rail roadbed due to the heavy rainfall. In this study, a large-scale laboratory test were conducted with simulation of static performance on the geotextile container reinforced rail roadbed. Based on the laboratory test results, the vertical pressure distribution with respect to the depth, and settlement of rail roadbed were measured and compared test results between geotextile container reinforced case and unreinforced case. Thus, the effectiveness of reinforcement was evaluated in terms of its performance and stability.

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Analysis of Settlement and Stress Characteristics about Influence of Track Parameters on Railroad Roadbed by using GEOTRACK (GEOTRACK을 이용한 궤도변수에 따른 침하 및 응력 특성 분석)

  • Shin, Eun-Chul;Lee, Han-Jin;Kang, Jeong-Gu;Yang, Hee-Saeng
    • Proceedings of the KSR Conference
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    • 2007.05a
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    • pp.395-403
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    • 2007
  • Railroad track consists of relatively simple structures such as rail, sleeper, ballast. Roadbed shares vertical pressure by train load which passed through rail to ballast as base that supports the track. For evaluating stress and displacement of roadbed due to the railroad load is an important role on the track as a basic data for estimation of the durability and design of the roadbed thickness. GEOTRACK program applied multi-layered theory was developed for analyzing railroad track structure. GEOTRACK program is a sort of numerical analysis program which has advantage that can analysis component of track by simple method. In this study, this program was used to preform the numerical analysis by changing track conditions and roadbed conditions such as tie, reinforced roadbed, dynamic wheel load, Resilient modulus and so on. Further detail will be presented on the paper.

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Development on Design Method for Railway Roadbed by Geocell System (지오셀을 이용한 철도노반의 설계기법 개발)

  • Shim, Jae-Bum;Shin, Min-Ho;Cho, Sam-Deok;Chae, Young-Su
    • Journal of the Korean Geosynthetics Society
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    • v.1 no.1
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    • pp.23-29
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    • 2002
  • Since 1980's in U.S.A and Japan, the studies on increasing the bearing capacity of railway roadbed using geocell system have been conducted for repair and reinforcement of railways constructed on soft soils. In this study, the railway roadbed reinforced with geocell system, used for repair and reinforcement of existing railways in Korea, has been analyzed and investigated the results of the previous studies conducted in Korea and other nations. And the method for estimating the railway roadbed thickness was developed based on the equivalent method using the multi-layer theory and the deformation modulus Ev.

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Development of Design Method for Reinforced Roadbed Considering Plastic Settlement for High-speed Railway (고속철도에서의 소성침하를 고려한 강화노반 설계기법 개발)

  • Choi, Chan-Yong;Choi, Won-Il;Han, Sang-Jae;Jung, Jae-Hyun
    • Journal of the Korean Geotechnical Society
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    • v.29 no.9
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    • pp.55-69
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    • 2013
  • An alternative design method of existing methods based on elastic theory the design method of roadbed considering plastic deformation of roadbed and stress-strain at roadbed materials with the cyclic loading of trains passing. The characteristics of the developed design method considering traffic load, number of cyclic loading and resilience modulus of roadbed materials can evaluate elastic strain as well as plastic settlement with allowable design criteria. The proposed design method is applied to standard roadbed section drawing of HONAM high-speed railway considering design conditions such as allowable elastic and plastic settlement, train speed, the tonnage of trains. As a result, required levels of resilience modulus model parameter ($A_E$), unconfined compressive strength, types of soil material were evaluated.

Behavior of Sand Bag for Maintenance Railroad Bed Subjected to Cyclic Loading (반복하중을 받는 철도노반보수용 샌드백의 거동분석)

  • Shin Eun-Chul;Hwang Seon-Keun;Lee Dong-Hyun;Ryu In-Gi
    • Proceedings of the KSR Conference
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    • 2004.06a
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    • pp.1033-1040
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    • 2004
  • Utilizing of the geotextile container shows several advantages such as standardized construction, factory manufactured products, the control of quality, workability. and economical point of view. Recently this technique can be applied to rehabilitate the loss of rail roadbed due to the heavy rainfall. In this study, a large-scale laboratory test were conducted with simulation of static performance on the geotextile container reinforced rail roadbed. Based on the laboratory test results, the vertical pressure distribution with respect to the depth, and settlement of rail roadbed were measured and compared test results between geotextile container reinforced case and unrein forced case. Thus, the effectiveness of reinforcement was evaluated in terms of its performance and stability.

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