• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1705-1711
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• 2008

Analysis of settlement of foundation under the cyclic loading is very important element in the field construction. The fatigue of construct is inflicted by wheel load of mobile unit with railroad and superhighway. The settlement behavior under the cyclic loading is investigated through Power Model by Li and Selig. However, the settlement tendency of foundation appears to be the settlement of general Europe cohesive soil. In this study, the Power Model was used to determine the plastic deformation for sandy soil. Based on the laboratory cyclic loading test a, m, b parameters, for using in the Power Model were presented.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.3
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• pp.183-198
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• 2021

The EPB (Earth Pressure Balanced) shield TBM method restrains the ground deformation through continuous excavation and support. Still, the significant surface settlement occurs due to the ground conditions, tunnel dimensions, and construction conditions. Therefore, it is necessary to clarify the settlement behavior with its influence factors and evaluate the possible settlement during construction. In this study, the analytical model of surface settlement based on the influence factors and their mechanisms were proposed. Then, the parametric study for controllable factors during excavation was conducted by numerical method. Through the numerical analysis, the settlement behavior according to the construction conditions was quantitatively derived. Then, the qualitative trend according to the ground conditions was visualized by coupling the numerical results with the analytical model of settlement. Based on the results of this study, it is expected to contribute to the derivation of the settlement prediction algorithm for EPB shield TBM excavation.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.449-454
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• 1998

This study was performed of the research for accurate prediction of consolidation settlement at initial consolidation time. In order to analysis the program is developed which is able to analysis behavior of settlement caused by gradual load increment, and simulated consolidation using whole measured settlement data and that from beginning of embankment to end of it. The former result agrees with measured data and the latter it overestimated 13% larger than measured data. It was found the time which takes to be eliminated effect of gradual step load. This method is compared with the results from Asaoka, Hyperbolic and Tan's hyperbolic method respectively Asaoka and Tan's hyperbolic methods we in good agreement with this method. But classical hyperbolic method overestimated about 32%.

• Journal of the Korean Geotechnical Society
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• v.26 no.1
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• pp.35-43
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• 2010

The behavior of the Top-Base foundation was investigated by carrying out 3D finite element method. Special attention is given to the settlement behavior of concrete Top-Base foundation due to the consolidation settlement of the embedding depth and the effect of footing dimensions which are not included in the practical design. To obtain the detailed informations, a series of numerical analyses were performed for different pile configurations. It is shown that as the number of piles in a group increases, the calculated settlement also increases. However, for the $7\times7$ group, there is no further increase in settlement. Based on this study, it is found that the total settlement of Top-Base foundation is highly influenced by the consolidation settlement and footing configurations. It is also found that the current design method overestimates the settlement, and thus, needs to be modified and supplemented.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.291-300
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• 2022

Tunnel boring machines combined with the earth pressure balanced shield method (EPB shield TBMs) have been adopted in urban areas as they allow excavation of tunnels with limited ground deformation through continuous and repetitive excavation and support. Nevertheless, the expansion of TBM construction requires much more minor and exquisitely controlled surface settlement to prevent economic loss. Several parametric studies controlling the tunnel's geometry, ground properties, and TBM operational factors assuming ordinary conditions for EPB shield TBM excavation have been conducted, but the impact of excessive excavation on the induced settlement has not been adequately studied. This study conducted a numerical evaluation of surface settlement induced by the ground loss from face imbalance, excessive excavation, and tail void grouting. The numerical model was constructed using FLAC3D and validated by comparing its result with the field data from literature. Then, parametric studies were conducted by controlling the ground stiffness, face pressure, tail void grouting pressure, and additional volume of muck discharge. As a result, the contribution of these operational factors to the surface settlement appeared differently depending on the ground stiffness. Except for the ground stiffness as the dominant factor, the order of variation of surface settlement was investigated, and the volume of additional muck discharge was found to be the largest, followed by the face pressure and tail void grouting pressure. The results from this study are expected to contribute to the development of settlement prediction models and understanding the surface settlement behavior induced by TBM excavation.

• Geomechanics and Engineering
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• v.9 no.3
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• pp.373-395
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• 2015

Comprehensive results from cyclic plate loading at a diameter of 300 mm supported by layers of geocell are presented. The plate load tests were performed in a test pit measuring $2000{\times}2000mm$ in plane and 700 mm in depth. To simulate half and full traffic loadings, fifteen loading and unloading cycles were applied to the loading plate with amplitudes of 400 and 800 kPa. The optimum embedded depth of the first layer of geocell beneath the loading plate and the optimum vertical spacing of geocell layers, based on plate settlement, are both approximately 0.2 times loading plate diameter. The results show that installation of the geocell layers in the foundation bed, increase the resilient behavior in addition to reduction of accumulated plastic and total settlement of pavement system. Efficiency of geocell reinforcement was decreased by increasing the number of the geocell layers for all applied stress levels and number of cycles of applied loading. The results of the testing reveal the ability of the multiple layers of geocell reinforcement to 'shakedown' to a fully resilient behavior after a period of plastic settlement except when there is little or no reinforcement and the applied cyclic pressure are large. When shakedown response is observed, then both the accumulated plastic settlement prior to a steady-state response being obtained and the resilient settlements thereafter are reduced. The use of four layers of geocell respectively decreases the total and residual plastic settlements about 53% and 63% and increases the resilient settlement 145% compared with the unreinforced case. The inclusion of the geocell layers also reduces the vertical stress transferred down through the pavement by distributing the load over a wider area. For example, at the end of the load cycle of the applied pressure of 800 kPa, the transferred pressure at the depth of 510 mm is reduced about 21.4%, 43.9%, 56.1% for the reinforced bases with one, two, and three layers of geocell, respectively, compared to the stress in the unreinforced bed.

• Journal of the Korean Geosynthetics Society
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• v.5 no.1
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• pp.15-23
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• 2006

Sand Compaction Pile and Stone Column method have been used in widely during several decades as a technique to reinforce soft soils and increasing ultimate bearing capacity, accelerate consolidation settlement of the foundation ground. Stone column method, making a compaction pile using crushed stone, is a soft ground improvement method. However, stone column method is difficult to apply to the ground which is not mobilized enough lateral confine pressure because no bulging failure resistance. Hence, in present study, development the geogrid reinforced stone column system for settlement reduction and wide range of application of stone columns. To develop this system, triaxial compression tests were conducted for evaluation which is about behavior characteristics of stone column on replacement rate and confine pressure. Then, 3-dimensional numerical analysis were evaluated for application of the GRSC (geogrid reinforced stone column) system as evaluate behavior characteristics and settlement reduction effect of stone column reinforced by geogrid on types and reinforcing depth change of geogrid.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.650-660
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• 2018

The approach slab plays an important role in the driving comfort of the connection section on a bridge. On the other hand, the approach slab only calculates the section force of a simple beam, and does not analyze the behavior. In this study, the unsupported length and settlement of approach slabs of IPM Bridges were examined using structural analysis. First, the section force was calculated by designing a simple beam, according to the length of the approach slab. The structural analysis was conducted to examine the behavior of the unsupported length and settlement. As the result, the bending moment decreased when the unsupported length was increased, and the bending moment increased when the settlement was increased. In addition, the design section force was estimated to be larger than the force of structural analysis, and the design of the approach slab according to the design guideline showed no problem in stability. Nevertheless, the vertical displacement exceeded the maintenance criterion of a 1/200 curve when the settlement exceeded 10 mm regardless of the unsupported length. Therefore, excessive settlement occurs in the reinforced earth retaining wall supporting the approach slab, and the design bending moment may be exceeded. Therefore, strict management is required.

• Proceedings of the Korean Geotechical Society Conference
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• 1996.10a
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• pp.25-38
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• 1996

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.8-16
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• 2018

This study examined the long-term behavior of a roadbed using high-speed railway concrete track and roadbed measurement data and evaluated the long-term performance of the track and roadbed. Recently, high-speed railway track type has been adopted as a concrete slab. On the other hand, the concrete track is vulnerable to roadbed settlement. In the case of gravel tracks, it is easy to restore the original state by maintenance even if the roadbed settles. On the other hand, in the case of the concrete track, if excessive settlement of the roadbed occurs, cracks are generated continuously on the slabs and sleepers, resulting in greatly reduced usability. For this reason, it is difficult to restore the original state only by partial maintenance. In this paper, a long-term performance evaluation was carried out on a concrete track during operation by monitoring the measurement data of sensors buried from the beginning of construction for approximately 3 years after the high-speed railway opened. Performance evaluation methods include a performance evaluation of track/roadbed when the train passes, long-term track and roadbed performance evaluation, analysis of the track/roadbed effect on long-term settlement and analysis of the factors influencing long-term settlement. The trail response of KTX-Sancheon was greatest in the track/roadbed performance evaluation by train. The results of the long-term track and roadbed performance evaluation were measured within the standard values. The track and roadbed performance impact assessment with long-term settlement was strongly related to TCL settlement. The influences of the water content and groundwater level were verified by analyzing the external factors of long-term settlement. Through such a method, the stability of a track/roadbed can be secured.