• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1165-1172
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• 2006

In this study, an aspect of settlement, developed from different ground improvement method like suction drain method using vacuum pressure and vertical drain method using overburden pressure, was compared each other. In order to analyze settlement tendency of each method exactly, the finite element analysis program was used. The analyses of vertical settlement and lateral displacement for suction drain method and vertical drain method were conducted independently during the solving stage. The initial condition of drainage zone was fixed with 25m depth and 21m width. After the program analyses, the settlement condition had a different tendency with the ground improvement method. Especially, in the results of vertical drain method, the disparity of settlement between the middle of improved zone and unimproved zone. In the case of suction drain method, however, the difference of settlement was smaller than that of vertical drain method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.715-722
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• 2016

Most of the domestic railroad tracks are ballast track and repetitive maintenance is required in this track. Therefore, it is necessary to optimize maintenance process for maintenance cost reduction and more effective maintenance. For this, it is important to develop a reasonable settlement progressive model of ballast layer. However, the behavior of ballast is different to that of soils, since ballast is composed of large coarse gravel. Thus, in this study, we carried out numerical analysis by using the discrete element method (PFC 2D) for better understanding of ballast settlement and development of reasonable settlement progressive model. And, we evaluated the settlement of ballast according to particles shape, porosity and loading conditions.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.69-77
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• 2007

In this study, the consolidation behavior of clayey ground improved by vertical drain method was analyzed by the finite difference method based on the three-dimensional elasto-viscous consolidation theory, which can express the behavior of the secondary consolidation without considering the distinction of the normally consolidated and overconsolidated states. And the applicability of the elasto-viscous consolidation theory was discussed by comparing with the test results obtained from the model test of ground improved by vertical drain system. From these results, it is found that the amount of the settlement when the excess pore water pressure almost dissipated in the clay ground with vertical drains became smaller than that of the one-dimensional condition, and then the amount and rate of the residual settlement at secondary consolidation process became larger than those of the one-dimensional condition. finally, the effect of soil parameter on behavior of consolidation process was investigated by the results of a series of numerical analysis for the normalized and overconsoldiated states.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.7-14
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• 2011

The numerical analyses were performed to investigate the curling behavior of the post-tensioned prestressed concrete approach slab (PTAS) under environmental loads. A technique to include properly the boundary conditions of one end of PTAS that was connected to the bridge abutment using hinges was proposed for the numerical model. The applicability of a simplified model not having hunches was also investigated. By using the developed models, the curling behavior of PTAS was analyzed when the foundation settlement occurred. The analysis results showed that the maximum tensile stress obtained from the simplified model involving a simplified hinge connection was very closed to that obtained from a rigorous model. When the slab curled up, the maximum tensile stress occurred in the model including no foundation settlement, but when the slab curled down, the maximum stress occurred in the model including partial settlement of the foundation. Therefore, the design of PTAS should be performed considering those maximum tensile stresses.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.689-705
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• 2017

The present study deals with the Pressure-settlement behavior of square and rectangular skirted footing resting on sand and subjected to a vertical load through a laboratory experimental study. A series of load tests were conducted in the model test tank to evaluate the improvement in pressure-settlement behavior and bearing capacity of square and rectangular model footings with and without structural skirt. The footing of width 5 cm and 6 cm and length/width ratio of 1 and 2 was used. The relative density of sand was maintained at 30%, 50%, 70%, and 87% respectively. The depth of skirt was varied from 0.25 B to 1.0 B. All the tests were carried out using a strain controlled loading frame of 50 kN capacity. The strain rate for all test was kept 0.24 mm/min. The results of present study reveal that, the use of structural skirt improves the bearing capacity of footing significantly. The improvement in bearing capacity was observed almost linearly proportional to the depth of skirt. The improvement in bearing capacity of skirted footings over footing without skirt was observed in the range of 33.3% to 68.5%, 68.9% to 127% and 146.7% to 262% for a skirt depth of 0.25 B, 0.50 B and 1.0 B respectively. The skirted footings were found more effective for sand at relative density of 30% and 50% than at relative density of 70% and 87%. The bearing capacity was found to increase linearly with footing width for footings with and without skirts. This observation was found to be consistent for footings with different skirt depths and for relative density of sand i.e., 30%, 50%, 70%, and 87%. The obtained results from the study for footing with and without skirts were comparable with available solutions from literature.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.415-422
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• 1999

The general concept of reinforced roadbed in the high-speed railway is to cope with the soft ground for the bearing capacity and settlement of foundation soil. The cyclic plate load tests were performed to determine the behavior of reinforced ground with multiple layers of geogrid underlying by soft soil. Five series of test were conducted with varying the soil profile conditions including the ground level, type of soil, and the thickness of each soil layer. Based on these plate load tests, laboratory model tests under cyclic loading were conducted to know the effect of geogrid reinforcement in particular for the high-speed rail roadbed. The permanent settlement and the behavior of earth pressure in reinforced roadbed subjected to a combination of static and dynamic loading are presented.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.663-670
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• 2003

Urban tunnelling need to consider not only the stability of tunnel itself but also the ground movement regarding adjacent structures. This paper present 3-D behavior of adjacent structures due to tunnelling induced ground movements by means of field measuring data and nonlinear FEM tunnel analysis. The results of the analytical methods from Mohr-Coulomb model are compared with the site measurement data obtained during the twin tunnel construction. It was found that the location and stiffness of the structure influence greatly the shape and pattern of settlement trough. The settlement trough for Greenfield condition was different from the trough for existing adjacent structures. Therefore the load and stiffness of adjacent structures should be taken into account for the stability analysis of the structures.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.417-424
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• 2005

Observed field behaviors are frequently different from the behaviors predicted in the design state due to several uncertainties involved in soil properties, numerical modelling, and error of measuring system even though a sophisticated numerical analysis technique is applied to solve the consolidation behavior of drainage-installed soft deposits. In this study, genetic algorithms are applied to back-analyze the soil properties using the observed behavior of soft clay deposit composed of multi layers that shows complex consolidation characteristics. Utilizing the program, one might be able to appropriately predict the subsequent consolidation behavior from the measured data in an early stage of consolidation of multi layered soft deposits. Example analyses for drainage-installed multi-layered soft deposits are performed to examine the applicability of proposed back-analysis method.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.205-212
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• 2001

This paper is experimental and numerical research about the sliding behavior of cantilever retaining walls resisting surcharge loads. In experimental research, centrifuge model tests at the lg and 40 g-level were performed by changing the location of model footing and its width. Bearing capacity of model footing and characteristics of load-settlement and load-lateral displacement of retaining wall were investigated. Test results of bearing capacity were compared with modified jarquio method, based on the limit equilibrium method with elasticity theory. For the numerical analysis, the commericially available program of FLAC was used by implementing the hyperbolic constitutive relationships to compare with test result about load-settlement and load-displacement of retaining wall, bearing capacity of strip footing.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.525-532
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• 2001

In this study, performance of reinforced railroad roadbeds with the crushed stones was investigated through the real scale railroad roadbed tests. Several real scale reinforced railroad roadbeds were constructed in the laboratory with different subgrade conditions and were tested with the estimated actual train loads including the impact loading of train. The affecting factors such as settlement, earth pressure and stress change at the surface of reinforced roadbed, subgrade layers as well as surface of rails were measured. It was found through the actual testing that for the roadbed with the same thickness, the settlement and vibration level (velocity) of reinforced roadbed decreases with the increase of reaction modulus of subgrade. The settlement of reinforced roadbed with the same reaction modulus of subgrade also decreases with the increase of thickness of the reinforced roadbed.