Honam High-speed Railway Research Articles

Development of liquid soil stabilizer (Ca2+) to reduce long-term embankment settlement

Honam High-Speed Railway in South Korea has suffered from long-term embankment settlement. The fines content in embankment material was pointed out as one of the causes. To reduce the settlement, Liquid Soil Stabilizer (LSS) was developed which is mainly composed of calcium chloride (CaCl2) or calcium hydroxide (Ca(OH)2). In this paper, the embankment materials consisting of low-plastic fines, which were represented by kaolinite-sand mixtures (20, 30, and 40% fines content), were treated by Liquid Soil Stabilizer (LSS) and the efficiency of LSS was evaluated by laboratory tests. For the application of LSS, the analysis of the engineering properties, compression behaviour, and creep settlement of embankment material including low-plastic fines was conducted. The LSS reduced the plasticity in all mixtures of soil as fines content increases. Application of the LSS could also provide better compaction efficiency and could reduce the void ratio change in one-dimensional compression. Therefore, to reduce long-term settlement of the embankment, the usage of LSS will be suitable as the on-site soil stabilization method without considering curing time.

Transfer Functions of Bridge and Train: Case Study of the Yunjung Bridge in Honam High-Speed Railway System

We propose the inverse transfer function (TFinv) changing the ground motion amplitude recorded at the train to the free-field equivalent ground motion supposing that the train is on the bridge. This process is needed to estimate the free-field motions from the seismic records observed at the on-board accelerometer which is used for the on-board earthquake warning system. To estimate the TFinv, evaluation of two transfer functions is needed: a transfer function of the bridge (TFbridge), and the other transfer function of the train (TFtrain). For the estimation of the TFbridge, we simplified an example bridge (named Yunjung bridge) located in the Honam high-speed railway as SDOF models finding its natural frequency dependent on the girder type and span length. Then, using time-domain integration methods (Newmark and Duhamel), SDOF response and TFbridge is calculated. For the TFtrain, we modeled the rail base and train following the similitude law and performed the shaking table test with various earthquake ground motions, and evaluated the TFtrain empirically comparing the responses at the train and the rail base. Two models of TFinv based on the moment magnitude ranges of input ground motions are proposed.

The Effect of Fines Content on Compressional Behavior When Using Sand–Kaolinite Mixtures as Embankment Materials

In South Korea, Honam High-Speed Railway has a relatively large residual settlement issue and high fines content has been pointed out as one of the causes. Design guidelines regulate not to use soils containing fines content higher than 25%. However, there is no background information on the effect of fines content on settlement. Therefore, this paper aims to investigate compressional behavior according to fines content using sand and kaolinite. Oedometer test results showed that the compression index is lowest with fines content of 15% to 20% at which the mixture produced maximum density. The optimum fines content for inducing low settlement would be 15% to 20% for the sand–kaolinite mixture. Transition fines content (TFC), which shows sand-like to claylike behavior, was observed to have between 21% and 26% of fines content. Critical fines content (fcrit) where a minimum void ratio occurs was estimated as 21.67%. These behavioral changes appear when fines content is greater than the optimum fines content. SEM also shows that the kaolinite particles were overlapped, creating flat surfaces with a fines content higher than 30%, and showing clay-like behavior. Based on the analysis results, engineers can simply identify the behavior of embankment materials to ensure optimum fines content and consequently minimize long-term settlement potential.

호남고속철도 교량의 동적 특성 현장 계측

2015년 개통한 호남고속철도는 개통전인 2013년 시험 운전을 통해 교량을 포함한 구조물의 안전성을 검토하였다. 당시 호남고속철도 일부 교량을 대상으로 중앙부 최대 처짐과 상판 연직 가속도 등 관련 기준 확보에 대한 검증실험을 수행한 바 있다. 본 연구는 호남고속철도 내 각기 다른 교량을 대상으로 교량의 동적 거동을 면밀히 살펴보기 위하여 2020년에 교량 동적 응답 현장계측을 수행하였다. 각 35m, 40m의 경간장을 가진 PSC Box 거더교와 50m 경간장의 소수주형 거더교를 대상으로 하부플랜지 중앙경간 외측면에 가속도계와 처짐계를 설치하였고, KTX 차량 통과 시 교량의 응답을 계측하였다. 계측한 응답을 바탕으로 교량의 동적특성(고유진동수, 감쇠비), 임계속도, 최대 응답, 충격계수, 그리고 공진의 정도를 분석하였다. 본 연구를 통해 KTX가 임계속도로 교량을 통과하여 공진이 발생할 경우, 교량의 동적거동을 심도 있게 이해할 수 있었다.

Analysis of Mobile Phone Data to Compare Mobility Flows and Hotspots Before and After the Opening of High-Speed Railway: Case Study of Honam KTX in Korea

Mobile phone data provides information, such as the home (origin) and current locations of people. The data can be used to analyze the impact of new high-speed railway (HSR) openings. This study examined the population observed in stations and cities of the Honam HSR line in Korea, based on mobile phone data recorded one year before and after its opening. We analyzed the volume of the population observed at each railway station, density of the distance between home and station, and activity hotspots in a city. The results show that the number of people and travel distance increased after the opening of the HSR. The distance to access railway stations increased, as the HSR saves travel time. Moreover, the activity hotspots in a city increased after the opening of the HSR, as more people gathered near the station area. The findings show that the mobility measures enhanced after the opening of the HSR for regional travel and local activities. These measures can help transit agencies and planners in providing better intercity travel.

Implementation of Image Processing in Studying Contact Conditions of Overhead Contact Line-Pantograph at 400 km/h

As an overhead contact line contacts the pantograph of an electric railway to supply electricity, it is operated after its electrical and mechanical safety features are examined. This study investigates a technology for examining the contact condition between the pantograph and the overhead contact line by using image processing. Contact condition images between the pantograph and the overhead contact line were obtained using a video device installed on the roof of a train, and the contact condition was tested between Iksan Station and Jeongeup Station of the Honam high-speed railway in the velocity range of 100–400 km/h. Images between the pantograph and the overhead contact line were used to recognize the feature points of the pantograph, and the moving displacement of the contact strip was detected using a Hough transform. The detected displacement was represented as a frequency through the zero crossing and a Fourier transform, and then its relationship with the arcing between the overhead contact line and the pantograph was analyzed.

Environment-vulnerability evaluation of a high-speed railway line in Korea using a groundwater-anomaly method

The Republic of Korea completed the first phase of the Honam high-speed railway from Seoul to Gwangju in 2014, and the second phase from Gwangju to Mokpo will be completed in 2025. This study evaluates the vulnerability of the groundwater environment in the Cheonan-Iksan zone, which passes through three preliminary lines (the Cheonan-Daejeon-Iksan line, Cheonan-Gongju- Iksan line, and Cheonan-Osong-Iksan line) of the Honam high-speed railway, to determine the most suitable line. The groundwater-level anomaly is evaluated along the three lines of the high-speed railway. The depth to water ranged from 0.03 to 21.1 m and from 0.17 to 227.95 m (AMSL). To determine a suitable line for the high-speed railway, a groundwater-level anomaly (GLA) grade is used, which considers the spatial distributions of the depth to water and groundwater elevation. Based on the GLA evaluation index, the Cheonan-Daejeon-Iksan (CDI) line exhibited the highest vulnerability (85.39), while the Cheonan-Osong-Iksan (COI) line had the lowest vulnerability (47.41). Vulnerable geological engineering, which is indicated by a discharge-estimation (DE) grade higher than 4, occurred in a section of the CDI line with a DE grade of 9, suggesting that attention should be directed to the discharge of groundwater during tunnel excavation.

Effect of Groundwater Level Variation on Residual Settlement of Korean High-Speed Railway on Soft Ground

Groundwater drawdown is one of the factors that inducoe settlement in soft ground. However, the drawdown usually does not lead to a large settlement, and thus is not considered at the design stage. A few sites along the Honam High-Speed Railway experienced relatively large residual settlements, judging from residual settlement criterion of 30 mm in Korea. This settlement occurred during the dry season in Korea; accordingly, groundwater drawdown was pointed out as a cause of the settlement. This study focuses on the effect of groundwater level variation on residual settlement by field measurement and numerical analysis. The numerical simulation produced reasonably similar settlement behavior to that of the field measurements, which proves that the numerical analysis represents field performance. The comparison of numerical analysis between the constant and variable groundwater level clearly shows the effect of groundwater variation on the settlement of soft ground. The drawdown only leads to additional residual settlements of 7.3 and 8.3 mm at the surface of the natural ground and embankment. The total residual settlement is approximately 21.9 mm; thus, more than 33% of the settlement was caused by groundwater drawdown. Therefore, the groundwater variation should be considered at the design and construction stages to reduce residual settlement in the case of strict criterion.

전과정평가(LCA)에 기반한 교통수단의 환경성 분석 : 호남고속철도의 온실가스 배출을 중심으로

전과정평가(LCA)에 기반한 교통수단의 환경성 분석 : 호남고속철도의 온실가스 배출을 중심으로

열차하중, 속도변화에 따른 토공상 콘크리트 슬래브궤도의 거동특성연구

In recent high speed rail way, the operating speed of train is enhanced and the introduction of EMU train vehicles is increased. In addition, as expected the demand of the concrete slab track and the trend of design cross-section reduction, the clear behavior of evaluation of internal slab layer is demanded about the variation of design load and speed. The purpose of this study is to evaluate and identify the mechanical behavior pattern of concrete slab track and track-road bed with the variation of axle load and train speed. To this end, the behavior of TCL and HSB was evaluated in according to the variation of axle load and speed. And the analysis results and the data measured TCL strain sensor, which was embedded in TCL slab under installation on Honam high speed railway, was analyzed. The analysis result shows that the strain are increasing in according to the speed-up of train, and line regression was obtained from measured data. Analysis data of the state of bonding condition of slab layer and measured data was analyzed. It is conducted that the TCL layer stress of HEMU 430X, which of axle load, is lighter was similar to the stress of KTX-Honam, the standard deviation of measured stress is dramatically increased.

Estimation of the vibration serviceability deflection limit of a high-speed railway bridge considering the bridge-train interaction and travel speed

The static and dynamic displacements of high-speed railway bridges, which are determined by the load conditions, travel speed, and span, may cause passenger discomfort when they are excessive. In the Korea Railway Bridge Design Specifications, the allowable deflection is based on the train travel speed. It is, however, not sufficient for considering the vibration serviceability. The Eurocodes has also been quoted in the design guidelines of the Korean Honam High-speed Railway (KRNA, 2007). For the determination of the vibration serviceability of a passenger train, the Eurocodes proposes a deflection limit based on the vibration serviceability obtained from the ratio of the deflection to the span and considers the bridge–train interaction. However, the maximum speed and maximum span in the Eurocodes are 350 km/h and 120 m, respectively. Moreover, it does not provide a detailed process for determining the deflection limit based on vibration serviceability. It is therefore difficult to use the deflection limit as the design limit in increasing the span and travel speed. Hence, to ensure passenger comfort and enable changes in railway techniques, it is necessary to develop a vibration serviceability-based deflection limit that flexibly responds to changes in the railway environment regarding bridge span and travel speed. This study was conducted to determine the deflection limits of Korean railway bridges based on their vibration serviceability and considering the bridge–train interaction and increase in travel speed. In this paper, the bridge–train transfer function is developed using a simplified bridge–train model comprising a single mass–spring system. It is then verified by dynamic analysis of the bridge–train interaction. A parametric study and bridge–train dynamic interaction analysis are used to determine the correlation between the vertical acceleration of a car body and the bridge displacement with increasing travel speed. In addition, the vertical acceleration of the car body is shown to increase with increasing travel speed, and an amplification coefficient of the vertical acceleration of the car body is suggested. Further, a vibration serviceability deflection limit for high-speed railway bridges is developed in this paper using the transfer function and the amplification coefficient. Here, the deflection and vibration of the bridge are assumed to be respectively sinusoidal and harmonic. The suggested vibration serviceability deflection limit is also compared with those in the Eurocodes and the Shinkansen.

실대형 실험을 이용한 가진주파수 변화에 따른 콘크리트궤도의 동적평가

호남고속철도에 부설된 동일한 궤도노반시스템을 실제 열차하중이 가능한 실대형 가진시험을 통해 성능을 평가하였다. 실험결 과 Odemark 등가깊이 이론에 의한 노반압력과 매우 유사한 것을 확인하였다. 콘크리트궤도에서 정적하중 330 kN을 재하시 노반 상부의 토압은 50 kPa 이내로 발생하였고, 정적하중시험과 반복하중시험 결과는 비교적 큰 차이가 없었다. HSB의 탄성변위는 증속시험 시 관리기준값 1 mm에 비해 약 1/100 수준이며, 노반의 탄성변위량과 비교해볼 때 1/175 정도로 매우 작은 변위가 발생하였다. 가진주파수의 크기에 따라 궤도노반의 동적거동은 가진주파수가 35 Hz이하에서는 모든 측정값이 거의 선형적으로 증가하였으나, 35 Hz이상에서는 윤중, 변위, 지반가속도 등이 감소하였다. In this study, the full scale model tests were performed with track-roadbed system such as Ho-nam high speed railway. The measured data gives good similar a roadbed pressure with equivalent depth to the Odemark's theory. In the case of earth pressures have a under 50 kPa at upper-subgrade applying 330 kN static loading. Results of cyclic loading tests did not differ significantly from those of static loading test. The elastic displacement at HSB layer has a level of 1/100 compared to the 1 mm that it was evaluation criteria for speed up of High Speed Railway. Elastic displacement at subgrade layer was measured a level of 1/175. The dynamic characteristics of track-roadbed with loading frequency level were linearly increased under 35 Hz, while the wheel loading, displacement and acceleration of roadbed were decreased loading frequency above 35 Hz.

400km/h 고속철도 대규모 계측데이터 사용자 중심 확장성 계측시스템

본 논문은 동력분산식 차세대고속열차가 최고속도 400km/h 이상으로 개발됨에 따라 차량의 최고속도 시험에 대비하여 호남고속철도 건설구간에서 인프라시스템 기술개발이 필요하여 국내에서는 유일하게 현재 호남고속철도 건설구간 중 28km 구간에서 400km/h급 고속철도 인프라를 구축하였다. 또한 계측장비의 설치 및 모니터링 시스템을 설치하여 선로의 지속적인 모니터링이 가능하도록 설계하였다. 이를 통해, 보다 포괄적이며 장기적인 관점에서 통합모니터링의 요구사항과 향후 연구방향을 확인할 수 있었다. Needs for a new technologies of infrastructure systems arose, following the development of next generation EMU(Electric Multiple Unit) train with maximum speed over 400km/h. For high-speed operation tests of the new EMU, a high-speed railway infrastructure test-bed was constructed in a 28km long section of the Honam High-speed Railway. Diverse sensors and monitoring system was installed for continuous monitoring of the railway. Due to such effort, further demands and needs of the integrated monitoring system was derived in a more comprehensive and long-term perspective.

고속철도에서의 소성침하를 고려한 강화노반 설계기법 개발

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 (), unconfined compressive strength, types of soil material were evaluated.

차세대고속열차 운행에 따른 호남고속선 강합성교의 동특성 분석

새로 개발된 차세대고속열차(HEMU-430X)가 400km/h 이상의 고속운행을 앞두고 있으나, 우리나라 철도설계기준은 350km/h이하의 운행속도에 대한 지침을 제시하고 있으며, 호남고속선도 350km/h이하의 기준을 적용하여 설계되었다. 350km/h를 초과하는 고속운행에 대해 기존 인프라의 성능을 검토하고, 고속운행을 대비한 설계기준 마련이 시급한 바, 이 연구에서는 증속에 대한 경부선 가야고가에 대해 시뮬레이션하고, 차세대고속열차(HEMU-430X) 시험운행 중 측정된 가야고가의 가속도, 변위 데이터를 비교, 검토하여 350km/h이상의 열차운행에 대한 강합성 소수주형교의 동적거동을 분석하였다. 경부고속선 가야고가 분석결과를 토대로 내년도 완공을 앞두고 있는 호남고속선 연정교에 대해 수치해석을 통해 실제 HEMU 시범운행시 발생할 수 있는 동적 거동을 예측하였다. The new developed train(HEMU-430X) faces running at high speed over 400km/h. But The Korea railway design code gives guidelines below 350km/h speed. Honam HighSpeed Railway was also designed based on the design standard below 350km/h. Existing infra structures have to be reviewed at high speed running and the design guideline for the speed over 350km/h should be prepared as soon as possible. This paper presents (1) the simulation results of composite steel girder bridge(Kaya Bridge of Seoul-Pusan HighSpeed Railway), (2) values measured at this bridge and the comparison with simulation results, and (3) the prediction of Yonjung bridge being constructed in Honam HighSpeed Railway.

열차의 주행속도와 차체연직가속도의 상관관계를 고려한 철도교량의 진동사용성 처짐 한계

In order to get dynamic serviceability of a train travelling on a railway bridge, comfort limits with the deflection of bridge and vertical acceleration on car body are proposed in Eurocode, Shinkansen design criteria, The design guideline of the Honam High-speed railway. The design guideline of the Honam High-speed railway has quoted Eurocode. Therefore it is expected that supplementation of comfort limit of railway bridge according to expansion of span length and the improvement traveling speed of trains in the future would relatively fall behind developed countries in railway. Therefore, in order to secure technological competitiveness in world market, the study was conducted to propose the deflection limit based on vibration serviceability of railway bridges that can consider bridge-train interaction and travelling speed increase. The parameter study and bridge-train dynamic interaction analysis was conducted to figure out the correlation of vertical acceleration on car body and bridge displacement according to the increase in travelling speed. Also, the trend of increasing vertical acceleration on car body according to the increase in travelling speed was confirmed, and the amplification coefficient of vertical acceleration on car body was suggested. And the deflection form and vibration of the bridge were assumed to be in harmonic motion, and transfer function and the amplification coefficient were used to develop the dynamic serviceability deflection limit of the high-speed railway bridge as a formula.

고속열차 주행 시 지진하중을 고려한 현수교의 주행안전성 및 승차감 분석

교량을 주행하는 열차의 주행안전성과 승차감의 확보를 위해 Eurocode, 신간선 기준, 호남고속철도 설계지침 등에서는 교량의 연직변위, 연직가속도, 면틀림 등의 항목으로 제한하고 있다. 그러나 이와 같은 제한 기준은 교량 설계자의 편의를 위한 간접적인 방법이다. 또한 이와 같은 기준은 일반적인 경간(Eurocode의 경우 120m 이하)에 대한 제한 기준으로서, 이 이상의 장경간 교량의 경우에는 교량/열차 상호작용 해석 등에 의한 면밀한 검토를 제안하고 있다. 본 연구에서는 교량/열차 상호작용 해석을 수행하여 열차에서의 응답을 통해 교량 상을 주행하는 열차의 주행안전성 및 승차감을 직접적으로 평가하고자 하였다. 즉, 중앙경간 300m의 현수교를 주행하는 KTX 열차에 대하여 열차 내부의 가속도와 윤중감소율을 구해 평가하는 방법을 취하였다. 또한, 이동 열차하중과 지진하중이 동시에 작용할 경우를 고려한 교량/열차/지진 상호작용해석을 수행하여 지진 시의 응답을 평가하였다. The estimation of traffic safety and passenger comfort when the train is running on the bridge is a estimation unique to the railway bridge. The standards for such estimation are included in the Eurocode, the Shinkansen design criteria, and the design guideline of the Honam High-speed railway. The items are bridge responses including vertical displacement of bridge, vertical acceleration, and slab twist. In principle, a direct estimation based on the train responses has to take place. However, the estimation based on the bridge responses can be seen as an indirect estimation procedure for the convenience of the bridge designer. First, it is general practice that traffic safety can be verified as a derailment coefficient or wheel load decrement The general method of estimating passenger comfort is to calculate the acceleration within the train car-body. Various international indexes have been presented for this method. In the present study, traffic safety and passenger comforts are estimated directly by bridge/train interaction analysis. The acceleration and wheel load decrement are obtained for the estimation of traffic safety and passenger comforts of a suspension bridge which has main span length of 300m. Also, the consideration of seismic load with simultaneous action of moving train is done for bridge/train/earthquake interaction analysis.