• Journal of the Korean Society for Railway
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• v.10 no.3 s.40
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• pp.264-270
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• 2007

Two modulus, strain modulus $(E_v)$ and subgrade reaction modulus $(K_{30})$ are being used as a standard for bearing stiffness in Korea Railroad design. The first is used in Europe and the other is used in Japan. The methodologies to obtain the two modulus are similar in using plate. But testing methods are different in loading to plate. Therefore, according to soil strain range, there should be large gap in not only computations of deformation modulus but also the necessary time to test. At first, this paper focuses on the two kinds of test methods to evaluate bearing stiffness. Secondly, based on elastic theory, the theory to obtain the two coefficients are studied thoroughly. Finally, the correlations between the two coefficients were analyzed and evaluated based on the field test results more than 38 places. The matching values for subgrade and ground between $K_{30}$ and $E_{v2}$ are proposed with the consideration of the proposed strain reduction factor (1.5 for subgrade and 3 for ground) and safety factor, respectively.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.57-67
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• 2008

Two test methods, nonrepetitive plate loading test (NPLT) and repetitive plate loading test (RPLT) are being used to control the quality of compaction through the evaluation of the stiffness of subgrade soils in the Korea railway industry. Subgrade reaction modulus ($k_{30}$) from the NPLT and strain modulus ($E_v$) from the RPLT are the index values to check them. The methods have similar aspects, but they differ in the modulus evaluation method, the numbers of loading stage, termination procedures, etc. This paper analyses the differences of the two test methods and evaluates the relationship between subgrade reaction modulus and strain modulus. In order to develop the relationship, total 22 tests were performed including the NPLT and the RPLT at the 6 original grounds, and 5 upper or lower subgrades in Kyungbu High Speed Railway II stage construction sites. According to the soil conditions, the relationship between subgrade reaction modulus and strain modulus was proposed with corrections by considering strain states, mean confining pressures, and Poisson's ratio.

• 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.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1279-1286
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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 has proposed a determination method of reinforced roadbed thickness using design chart made by resilience modulus and properties of earthwork materials.

• International Journal of Highway Engineering
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• v.1 no.1
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• pp.107-119
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• 1999

The joints in the jointed concrete pavement provide a control against transverse or longitudinal cracking at slab, which may be caused by temperature or moisture variation during or after hydration. Without control of cracking, random cracks cause more serious distresses and result in structural or functional failure of pavement system. However, joints nay cause distresses due to its inherent weakness in structural integrity. Thus, the evaluation at joint is very important. and the joint-related distresses should be evaluated reasonably for economic rehabilitation. The purpose of this paper was to develop an evaluation system at joints of jointed concrete pavement using finite element analysis program, ILLI-SLAB, and nondestructive testing device. FWD. To develop an evaluation system for JCP, a sensitivity analysis was performed using ILLI-SLAB program with a selected variables which might affect fairly to on the performance of transverse joints. The most significant variables were selected from precise analysis. An evaluation charts were made for jointed concrete pavement by adopting the field FWD data. It was concluded that the variables which most significantly affect to pavement deflections are the modulus of subgrade reaction(K) and the modulus of dowel/concrete interaction(G), and limiting criteria on the performance of joints at JCP are 300pci. 500,000 lb/in. respectively. Using these variables and FWD test, a charts of load transfer ratio versus surface deflection at joints were made in order to evaluate the performance of JCP. Practically, Chungbu highway was evaluated by these evaluation charts and FWD field data for jointed concrete pavement. For Chungbu highway, only one joint showed smaller value than limiting criterion of the modulus of dowel/concrete interaction(G). The rest joints showed larger values than limiting criteria of the modulus of subgrade reaction(K) and the modulus of dowel/concrete interaction(G).