• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.299-304
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• 2010

We should manage the target locations according to the deterioration degree of the ballast for the rational and economical ballast cleaning. For this, it's required to define the logics calculating the crushing rates and suggest the threshold values for the ballast cleaning. This paper introduce the system modules that estimate the ballast's deterioration degree refers to the results of the previous study("A Study on the Crushing Characteristic of the Ballast Gravel at High-Speed Railroad", Journal of the Korean Society for Railway, Vol.11, No.4, pp.384~389), enroll the target locations where the ballast cleaning is required.

• Structural Monitoring and Maintenance
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• 제9권1호
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• pp.1-27
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• 2022

Extensive laboratory tests were conducted to investigate the effect of load amplitude, geogrid position, and number of geogrid layers, thickness of ballast layer and clay stiffness on behavior of reinforced ballast layer and induced strains in geogrid. A half full-scale railway was constructed for carrying out the tests, the model consists of two rails 800 mm in length with three wooden sleepers (900 mm × 10 mm × 10 mm). The ballast was overlying 500 mm thickness clay in two states, soft and stiff state. Laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid. Settlement in ballast and clay, soil pressure and pore water pressure induced in the clay were measured in reinforced and unreinforced ballast cases. It was concluded that the effect of frequency on the settlement ratio is almost constant after 500 cycles. This is due to that the total settlement after 500 cycles, almost reached its peak value, which means that the ballast particles become very close to each other, so the frequency is less effective for high contact particles forces. The average maximum vertical stress and pore water pressure increased with frequency.

• 한국철도학회논문집
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• 제8권1호
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• pp.6-14
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• 2005

The mechanism of ballast-flying phenomena by strong wind induced by high-speed trains has extensively been investigated by conducting wind tunnel test and field-measuring of wind velocity in the vicinity of the track. The ballast gathered from the Seoul-Busan high-speed railway track has been classified by mass and shape to find relationship between those properties and the characteristic of movement in high wind and 16-channel Kiel-probe array has been used to examine the detailed flow structure above the surface of the track. The probability of ballast-flying during the passage of the high-speed train has been assessed comparing the results from wind tunnel test and that from field-measuring. The results shows that when the G7 train runs well as the KTX train runs at 300km/h, about 25m/s wind gust is induced just above the tie and the probability far small ballast under 50g to fly is about 50％ when it is on the tie. If the G7 train runs at 350km/h, the wind gust just above the tie increases to 30m/s, therefore radical countermeasure seems to be needed.

• Smart Structures and Systems
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• 제21권4호
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• pp.435-448
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• 2018

This paper reports the development of a theoretically rigorous method for permanent way engineers to assess the condition of railway ballast under a concrete sleeper with the potential to be extended to a smart system for long-term health monitoring of railway ballast. Owing to the uncertainties induced by the problems of modeling error and measurement noise, the Bayesian approach was followed in the development. After the selection of the most plausible model class for describing the damage status of the rail-sleeper-ballast system, Bayesian model updating is adopted to calculate the posterior PDF of the ballast stiffness at various regions under the sleeper. An obvious drop in ballast stiffness at a region under the sleeper is an evidence of ballast damage. In model updating, the model that can minimize the discrepancy between the measured and model-predicted modal parameters can be considered as the most probable model for calculating the posterior PDF under the Bayesian framework. To address the problems of non-uniqueness and local minima in the model updating process, a two-stage hybrid optimization method was developed. The modified evolutionary algorithm was developed in the first stage to identify the important regions in the parameter space and resulting in a set of initial trials for deterministic optimization to locate all most probable models in the second stage. The proposed methodology was numerically and experimentally verified. Using the identified model, a series of comprehensive numerical case studies was carried out to investigate the effects of data quantity and quality on the results of ballast damage detection. Difficulties to be overcome before the proposed method can be extended to a long-term ballast monitoring system are discussed in the conclusion.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.678-683
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• 2002

Field measurements were conducted to analysis dynamic characteristics of existing steel plate girder railway bridges without ballast. Three bridges which have 9m, 12m, 18m span length in Kyoung-Bu and Ho-Nam Line were selected for test. According to the each bridge, dynamic vertical deflections and vertical and horizontal accelerations were measured. Natural frequencies, vertical deflections and accelerations obtained from field tests were compared with the limit value specified in the UC, Japanese and Korean railway bridge specification.

• Geomechanics and Engineering
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• 제35권5호
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• pp.475-486
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• 2023

Ballast particles have an irregular shape and are discrete in nature. Due to the discrete nature of ballast, it exhibits complex mechanical behaviour under loading conditions. The discrete element method (DEM) can model the behaviour of discrete particles under a multitude of loading conditions. DEM is used in this paper to simulate a series of three-dimensional direct shear tests in order to investigate the shear behaviour of railway ballast and its interaction at the microscopic level. Particle flow code in three dimension (PFC3D) models the irregular shape of ballast particles as clump particles. To investigate the influence of particle size distribution (PSD), real PSD of Indian railway ballast specification IRS:GE:1:2004, China high-speed rail (HSR) and French rail specifications are generated. PFC3D built-in linear contact model is used to simulate the interaction of ballast particles under various normal stresses, shearing rate and shear box sizes. The results indicate how shear resistance and volumetric changes in ballast assembly are affected by normal stress, shearing rate, PSD and shear box size. In addition to macroscopic behaviour, DEM represents the microscopic behaviour of ballast particles in the form of particle displacement at different stages of the shearing process.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(II)
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• pp.27-34
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• 2003

This Study is about adoption of slab track on the new high speed railway line between Daegu and Busan. While ballast track currently used is easy to construct with low investment, the error margin of rail track occurs in the track due to the repetition load of the train. Therefore, repairs should be carried out all the time to put the railway track at the repair level or less. In addition, noise caused by such repairs has become a new social problem at night. Construction costs for slab track are about 1.3-1.5 times higher than those for ballast track. However, slab track will save labor costs by solving various problems of ballast track. In this regard, it is feasible to adopt slab track on the new high speed railway line between Daegu and Busan.

• 한국철도학회논문집
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• 제11권4호
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• pp.384-389
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• 2008

궤도구성품 중 도상은 레일과 침목으로 전달되는 열차하중을 노반으로 전달하는 중간매개체 역할을 하며, 도상자갈의 열화는 궤도틀림 진전에 직접적으로 영향을 미친다. 본 연구에서는 대형 보선장비(멀티플 타이 탬퍼; MTT; Multiple Tie Tamper)를 사용한 도상다짐작업과 누적통과톤수가 자갈 세립화 및 도상열화의 주요 원인이다. 도상자갈의 열화특성을 파악하기 위하여 시험용 궤도 부설을 통한 현장실험(2장. 실외 실측시험)과 실제의 운행 환경을 모사한 모형실험(3장. 실내 모형실험)을 실시하였고 실제 운용중인 고속선에서 채취한 시료의 파쇄입자 비율과 비교분석하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.162-166
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• 2011

In railway, Tie supports rail and plays a role that distribute train load to the ballast. Also, Tie and ballast resist against external force and fix the track position. But, weakening resistance of ballast and tie cause vertical displacement of tie and track irregularity. For reinforcement of track stiffness and reduction of track irregularity, KORAIL has developed Multi Branch type tie(GLORY Tie) that reinforced resistance than general PCT and installed in order to test in the field. This study measured and analyzed lateral resistance of ballast, wheel load of rail, bending strain of rail foot, vertical displacement and vibration acceleration of tie in order to evaluate performance of Multi Branch type tie in the field. According to the results of test, Multi Branch tie is excellent than general tie about lateral resistance of ballast and vertical displacement of tie. And, gap of measurement value between Multi Branch type tie and general tie about wheel load of rail, bending strain of rail foot were very small.

• 한국철도학회논문집
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• 제9권6호
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• pp.784-791
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• 2006

This paper presents the test results to evaluate the healthiness of the ballast in subway. The test includes the dynamic load test in servicing Line the screen classification test of aggregates and the wear test. From the results, the aspect and the property of the ballast are evaluated. The dynamic load tests explain the relationship between the deterioration of the ballast and the fluctuation of loads. The assessment of impact factor based on the field test results in a good property of test blocks is proposed.