• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3166-3171
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• 2011

The design standard for the thickness of reinforced roadbed is divided into high-speed and conventional railroad because dynamic characteristics of train loadings differ depending on the train speed. Due to the national plan for increasing the train speed for both conventional and new railroad lines, it is necessary to examine the applicability of concrete tracks and feasibility of the train speed increase on the conventional lines with the current thickness of the reinforced roadbed. In this study, a real-scale test was performed to monitor the dynamic characteristics of the reinforced roadbed with a thickness of 20cm and the train speed of 200km/h, 300km/h, and 400km/h. The test results were then compared with the design code to investigate the applicability of the conventional reinforced roadbed when the trains operate with higher speed.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.627-632
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• 2005

The reinforcing subgrade has the many advantages to maintain the quality of ballast track. It has also the function to prevent the softening of subgrade by mud-pumping. Therefore, active application of it is being expected for the future constructions of Korean railroad. In this paper, behaviors of the reinforced subgrade applied to conventional railroad were investigated through 3-D numerical analyses. The applicability of the reinforced subgrade to conventional railroad was evaluated by analyzing the distributions of the settlements and vertical stress of reinforced subgrade.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.404-411
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• 2007

Reinforced roadbeds are valued from the point of view of maintenance as well as enhanced mechanical capacity. They support more train load and less transmit to the sub-layers than general roadbeds. Also, the lateral sloping surface of the reinforced roadbed and its low permeability, achieved by the controlled compaction, increase drainage capability and prevent the softening of sub-layers. In the study, a series of cross-hole tests was performed to observe the temporal changes in the stiffness of reinforced roadbeds, if any, due to the cyclic loading of trains and alternating rainy and frozen seasons at Pyeong-taek experimental site. The three types of reinforced roadbed materials are slag, crushed stones, and soils, and the thickness of all the reinforced roadbeds is 0.8m. The stiffness of the slag and soil reinforced roadbeds was not changed or slightly decreased. The stiffness of the crushed stone was somewhat increased and is inferred to being densified close to surface.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1242-1247
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• 2007

An active application of concrete track is being expected for the future constructions of Korea railroad. For the successful construction and design in embankment section, the roadbed behavior should be reasonably estimated using the proper analysis method. In this research, behaviors of reinforced roadbed constructed with the determined stiffness and thickness at embankment section were estimated through various design parameters and numerical analysis. A three dimensional finite element method was employed to determine the proper reinforced roadbed thickness at embankment section. The displacement and vertical stress caused by train loading were estimated and compared with the field test results. The bearing characteristics of concrete track roadbed were presented. Moreover, the method to determine thickness of reinforced roadbed was proposed.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1115-1122
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• 2011

Reinforced-Roadbed materials are usually composed of crushed stones. Repeated load application can induce deformation in the reinforced-roadbed layer so that it causes irregularity of track. Thus it is important to develop a prediction model of elastic modulus based on stress-strain relation under repeatitive load in order to investigate behavior of reinforced roadbed. The prediction model of elastic modulus of the material can be obtained from repeated triaxial test. However, a proper size of the sample for the test must be used. In this study, a large repeatitive triaxial test apparatus with the sample size of diameter of 30 cm and height of 60cm was adapted for performing test of the crushed stone reinforced-roadbed considering large particle size to get resilient modulus Mr. The obtained resilient modulus was compared to shear modulus obtained from mid size resonant column test. The sample size effect is somewhat large enough so that it is required to design a scale factor based on similarity law in order to use smaller samples for getting elastic modulus of the crushed stone reinforced-roadbed material. A scale factor could be obtained from this study.

• 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.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1827-1832
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• 2007

The purpose of a railway track is to provide a smooth surface for safe and economical train transportation. The performance of the track results from a complex interaction of the track and subgrade components in response to train loading and environmental actions. In the past, the role of subgrade as the track foundation were not recognized adequately. There are insufficient information and inadequate methods for subgrade design, assessment and improvement. This situation has survived for a long time largely because a subgrade defect can often be adjusted by adding more ballast under the ties or applying more frequent track maintenance. Therefore, the application of reinforced roadbed technology will be expected to increase in the future. The reinforced roadbed thickness is set depending on subgrade reaction modulus$(K_{30})$ in the condition of upper subgrade through PBT in both conventional railroad and KTX railroads. As train velocity (V), train passing tonnage (N), and train axial load (P) are not considered in design, the roadbed thickness could be overestimated (or underestimated). Therefore, In this study, the computer model, GEOTRACK, was analyzed the influence of reinforced roadbed thickness factors on track modulus and the characteristics of stress pulses in track and subgrade generated by repeated axle loading.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.797-804
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• 2019

The two Koreas agreed to pursue rail and road connections on September 19, 2018 in the Pyongyang Joint Declaration. In December 2018, they launched a joint investigation for the North Korean railway modernization project. The survey confirmed that the track condition is seriously aging so that it is impossible to operate, and the railway network is well connected to major cities. Therefore, it was reasonable to modernize the aging track of the existing railway network rather than construct a new railway network. This paper proposed the railway communication policy for the improvement of railway lines and the construction of the railway wireless network by analyzing the status of roadbeds and tracks in order to enhance interoperability for the inter-Korean railway connection and safety for preventing the railway accidents.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.215-222
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• 2000

The reinforced roadbed should have the ability to spread out the load intensity lower than the bearing capacity of the subgrade of track structure as well as to prevent the softening of roadbed by providing appropriate stiffness in the roadbed, thus fully supports the track structures. Full scale reinforced roadbeds with several different types of monotoring sensors was also constructed to evaluate the performance of each reinforced roadbed through the continuous monitoring while the train operation. In this study, Field tests such as PLT, SASW were also carried out at each reinforced roadbed. The results of the field and lab tests, installation and calibration of sensors, as well as construction condition of the reinforced roadbed are presented.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1833-1837
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• 2007

The railroad roadbed plays an important role in distributing and transferring the train loading to subgrade, preventing subgrade from bearing softened by providing appropriate stiffness for subgrade, and eventually supporting the track structures. Presently, the reinforced roadbed was widely constructed in high speed line and is proceeding a research about economical thickness and methodologies for the design of reinforced roadbed. Field test section is located at Kongbu line which is from Suwon to Pungtack. In this study, field test were measured a track irregularity with several types of reinforced roadbed materials by using Track Master. The field testing were conducted between March, 2006 and March, 2007.