• Title, Summary, Keyword: roadbed pressure

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Characteristics of Behavior of the Crushed Stone Reinforced Roadbed under Cyclic Loading (동적하중 재하시 쇄석강화노반의 거동 특성)

  • 황선근;이성혁;이일화;최찬용
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.525-532
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    • 2001
  • In this study, performance of reinforced railroad roadbeds with the crushed stones was investigated through the real scale railroad roadbed tests. Several real scale reinforced railroad roadbeds were constructed in the laboratory with different subgrade conditions and were tested with the estimated actual train loads including the impact loading of train. The affecting factors such as settlement, earth pressure and stress change at the surface of reinforced roadbed, subgrade layers as well as surface of rails were measured. It was found through the actual testing that for the roadbed with the same thickness, the settlement and vibration level (velocity) of reinforced roadbed decreases with the increase of reaction modulus of subgrade. The settlement of reinforced roadbed with the same reaction modulus of subgrade also decreases with the increase of thickness of the reinforced roadbed.

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Roadbed Behavior in Managanese Crossing of Turnout System (분기기 망간 크로싱부 노반거동)

  • Jeon, Sang-Soo;Eum, Ki-Young;Kim, Jae-Min
    • Journal of the Korean Geotechnical Society
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    • v.24 no.2
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    • pp.45-57
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    • 2008
  • The improved turnout system is developed to speed-up the pre-existing railroad. The research has been actively carried out far the improved turnout system and the impact factor is estimated using the data sets achieved from the dynamic wheel-load field tests in both the conventional and the improved turnout system. In this study, the track performance and roadbed behavior are examined for the conventional and improved turnout system using the estimated impact factor. Dynamic wheel load and rail pressure are evaluated to assess the track performance. Roadbed stress and settlements are estimated using numerical analysis. Additionally, the stability of roadbed is estimated in soft roadbed condition influenced by the weather effects and cyclic train loading. The results show that dynamic wheel load, rail pressure, roadbed stress, and roadbed settlements in the improved turnout system substantially decrease compared with those in the conventional turnout system.

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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    • 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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Application of in-situ testing Methods for Bearing Capacity Estimation of Railroad Roadbed (철도 노반의 지지력 평가를 위한 현장 시험법 적용성 연구)

  • Park, Chang-Woo;Choi, Chan-Yong;Lee, Il-Wha;Kim, Dae-Sang
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.866-875
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    • 2006
  • The field plate load test a good potential for determining modulus since it measures both plate pressure and settlement. However, because The field plate load test is expensive and takes plenty of time for operation, it is very difficult to figure out the test characteristics of railroad roadbed in detail. For faster and economical operation, the Dynamic Cone Penetrometer(DCP) and the Light Falling Weight Deflectometer(LFWD) have been utilized for estimating the bearing capacity of railroad roadbed. The objective of this study is to determine the relationship between the test(PLT, DCP, LFWD) of the railroad roadbed in Korea. The DCP test and LFWD test for evauluating the strength of railroad roadbed materials produced in Korea are presented in this paper.

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Characteristics of Roadbed Behaviors of Concrete Track for High-Speed Railway (고속철도 콘크리트궤도용 흙노반의 거동 특성)

  • Lee Il-Wha;Lee Su-Hyung;Kang Yun-Suk
    • Journal of the Korean Society for Railway
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    • v.9 no.3
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    • pp.298-304
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    • 2006
  • An active application of concrete track is being expected for the future constructions of Korean railroad. For the successful concrete track construction and design in earthwork areas, the roadbed behavior should be reasonably estimated using the proper analysis method. In this paper, behaviors of concrete track on the reinforced roadbed constructed with the standard stiffness and depth were estimated thorough numerical analyses and field measurements. A three dimensional finite difference method was employed to model the concrete tracks and subground. The settlement and vertical pressures caused by train load were estimated by the numerical method and compared with the field measurement results. The bearing characteristics of roadbed were presented and the proper method for the analysis of concrete track was proposed.

Frost Heaving Pressure and Physical Characteristics of the Railway Roadbed Materials (철도노반재료의 동상팽창압 및 물리적 특성 평가)

  • Shin Eun-Chul;Park Jeong-Jun;Kim Jong-In
    • Journal of the Korean Society for Railway
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    • v.8 no.1
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    • pp.57-62
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    • 2005
  • The frost heaving pressure can be a problem for weakening of the railway roadbed material. This study was initiated to investigate the soils frost heaving pressure and physical characteristics(Liquid limit, permeability, SEM analysis) resulting from freezing and freezing-thawing cycle process. Therefore, upon freezing a saturated soil in a closed-system from the top, a considerable pressure was developed. Weathered granite soils, sandy soil were used in the laboratory freezing test which sometimes subjected to thermal gradients under closed-systems. The frost heaving pressure arising within the soil samples and the temperature of the samples inside were monitored with elapsed time. The degree of saturation versus heaving pressure curve is also presented for weathered granite soil and the maximum pressure is closely related to this curve. Based on the laboratory test results, fine-grained soils with strong attractive forces between soil grains md water molecules, and additional water is attracted into the pores leading to further volume changes and ice segregation.

Tilting Train-induced Roadbed Response on the Conventional Line (틸팅열차 주행시 기존선 흙 노반의 응답특성)

  • Koh, Tae-Hoon;Kwak, Yeon-Suk;Hwang, Seon-Keun;SaGong, Myung
    • Journal of the Korean Society for Railway
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    • v.14 no.5
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    • pp.433-441
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    • 2011
  • It is a fact that the straightening of track alignment is one of the undoubted ways to improve the train speed on conventional lines, while that requires huge investment resources. Therefore, the operation of a tilting train as well as the minimum improvement of track is suggested as an effective and economical alternative way for the speed-up of conventional lines. Since a driving mechanism of tilting train is different from those of existing trains, in order to make sure its operation safety and stability on conventional line, the performance of track and roadbed must be preferentially evaluated on the conventional line. Furthermore, it is necessary to estimate the tilting-train-induced roadbed response in detail since the roadbed settlement can lead to the track deformation and even derailment. In this research, the patterns of wheel load and lateral force were monitored and analyzed through the field tests, and the derailment coefficient and degree of wheel off-loading were calculated in order to evaluate the tilting train running safety depending on the running speeds (120km~180km) on the conventional line. Moreover, roadbed pressure, settlement and acceleration were also observed as tilting-train-induced roadbed responses in order to estimate the roadbed stability depending on the running speeds. Consequently, the measured derailment coefficient and degree of wheel off-loading were satisfied with their own required limits, and all of the roadbed responses were less than those of existing high-speed train (KTX) over an entire running speed range considered in this study. As a result of this study, the tilting train which will be operated in combination with existing trains is expected to give no adverse impact on the conventional line even with its improved running speed.

Long-Term Measurement under the Moving train at the Test Reinforced Roadbed Site in Railway (철도강화노반 시험부설구간에서의 열차 주행시 장기거동 계측)

  • 황선근;신민호;이성혁;최찬용;이시한
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.223-230
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    • 2001
  • Nine different types of the reinforced railroad roadbeds which . are located in between Suwon-Chunan station of Kyongbu line were constructed in order to increase the bearing capacity of railroad roadbed and to improve the ridability as a part of speed-up project of conventional railroad systems. Each three sections were composed of weathered granite soil, crushed stone and furnace slag(HMS25), and fully instrumented with earth pressure cells, settlement plates and geophones to monitor the behavior of roadbeds under actual train loads. Field measurement has continued since October 31, 2000 and presently with rather longer measurement interval. The measurement data such as settlement, earth pressure and vibration levels are currently under analysis process. In this paper, only cumulative measurement data of railroad roadbeds were introduced. In the near future, comprehensive measurement data and result of analysis will be presented and design technique for the reinforced railroad roadbed will be proposed as a final product of this study.

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Behavior Characteristics of Ballasted Track on Asphalt Roadbed Using Real Scale Test (실대형 실험을 통한 아스팔트 노반상 자갈궤도의 거동 특성)

  • 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.252-260
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    • 2015
  • Ballasted track on an asphalt roadbed can be beneficial for its various effects such as (i) decreasing of roadbed thickness by dispersing train load; (ii) prevention of both strength reduction and weakening in roadbed system by preventing rainwater penetration; and (iii) reducing maintenance cost by preventing roadbed mud-pumping and frostbite. With these beneficial effects, ballasted track on asphalt roadbed has been widely used in Europe and Japan, and relevant research for applying such ballasted track on asphalt roadbed systems in Korea is ongoing. In this study, full-scale static and dynamic train load tests were performed to compare the performance of ballasted track on asphalt roadbed and ballasted track. The optimum thickness levels of asphalt and reinforced roadbeds, corresponding to the design criteria for reinforced roadbed of high-speed railway, was estimated using the FEM program ABAQUS. Test results show that the earth pressure on reinforced roadbed of ballasted track on the asphalt roadbed was relatively low compared with that of simple ballasted track. The elastic and plastic displacements of simple ballasted track on the asphalt roadbed were also lower than those of ballasted track. These test results may indicate that the use of ballasted track on asphalt roadbed is an advantageous system in view of long-term maintenance.

Behavior of High-Speed Rail Roadbed Reinforced by Geogrid under Cyclic Loading (지오그리드로 보강한 고속철도 노반의 거동 특성)

  • 신은철;김두환
    • Journal of the Korean Society for Railway
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    • v.3 no.2
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    • pp.84-91
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    • 2000
  • The general concept of reinforced roadbed in the high-speed railway is to cope with the soft ground for the bearing capacity and settlement of foundation soil. The cyclic plate load tests were performed to determine the behavior of reinforced ground with multiple layers of geogrid underlying by soft soil. With the test results, the bearing capacity ratio, elastic rebound ratio, subgrade modulus and the strain of geogrids under loading were investigated. Based on these plate load tests, laboratory model tests under cyclic loading were conducted to estimate the effect of geogrid reinforcement in particular for the high-speed rail roadbed. The permanent settlement and the behavior of earth pressure in reinforced roadbed subjected to a combination of static and dynamic loading are presented.

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