• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.51-60
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• 2023

Unlike the vertical drilling in the directional drilling should be minimized torque and drag in the well trajectory that avoided problems such as drillstring transformation, casing wear and key-seating. These torque and drag magnitude is determined by variations such as the well trajectory geometry, drilling mud, drillstring type and kick-off point. Therefore, it is essential to consider these variations for designing directional well trajectory. In this study, it was selected well trajectory by the most common build-hold type well and calculated torque and drag on each section by Analytical friction model. Analysis indicates that torque and drag could be minimized by using high lubricity drilling mud, kick-off point appropriate according to the well geometry and possible minimize dogleg severity. The results of this study is useful to minimize torque and drag from directional well trajectory design.

• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.334-341
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• 2008

Ballast track needs maintenance works because it is supported by the compressible trackbed and subgrade layers. Maintenance works are essential to secure riding comfort and extend the life cycle of it. The necessities of maintenance works are determined from track irregularities measured by EM120. Track irregularities is the results of the track deformation. Therefore, it is natural to evaluate the cause of it. This paper focuses on the points the track irregularities come from the trackbed and the subgrade. Nondestructive techniques, such as Ground Penetrating Radar (GPR) and Portable Falling Weight Deflectometer (PFWD) are applied to evaluate the trackbed conditions, ballast layer thickness and vertical track stiffness, in the test section 500m long of Gyungbu line. The trackbed investigation results are compared with the track irregularities measured by EM120 and maintenance works. Conclusively, it was found that some maintenance works were unnecessary on the test section.

• Journal of the Korean Geotechnical Society
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• v.35 no.2
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• pp.5-17
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• 2019

Dynamic centrifuge model test was conducted to evaluate the dynamic stability of the pile-supported slab track method during dynamic railway loading and earthquake loading. The centrifuge tests were carried out for various condition of embankment height and soft ground depth. Based on test results, we found that the bending moment was increased with embankment height and decreased with soft ground depth. In addition, it was confirmed that the pile-supported slab track system could have dynamic stability for short-period seismic loading. However, in case of long-period seismic loading, such as Hachinohe earthquake, the observed maximum bending moment reached to pile cracking moment at the return period of 2,400 year earthquake. The criterion of ratio between embankment height and soft ground depth was suggested for dynamic stability of pile-supported slab track system.