• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.355-373
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• 2017

Tunnelling in urban areas, it is essential to understand existing structure-tunnel interactive behavior. Serviced structures in the city are supported by pile foundation, since they are certainly effected due to tunnelling. In this research, thus, pile load distribution and ground behavior due to tunnelling below grouped pile were investigated using laboratory model test. Grouped pile foundations were considered as 2, 3 row pile and offsets (between pile tip and tunnel crown: 0.5D, 1.0D and 1.5D for generalization to tunnel diameter, D means tunnel diameter). Soil in the tank for laboratory model test was formed by loose sand (relative density: Dr = 30%) and strain gauges were attached to the pile inner shaft to estimate distribution of axial force. Also, settlements of grouped pile and adjacent ground surface depending on the offsets were measured by LVDT and dial gauge, respectively. Tunnelling-induced deformation of underground was measured by close range photogrammetric technique. Numerical analysis was conducted to analyze and compare with results from laboratory model test and close range photogrammetry. For expression of tunnel excavation, the concept of volume loss was applied in this study, it was 1.5%. As a result from this study, far offset, the smaller reduction of pile axial load and was appeared trend of settlement was similar among them. Particulary, ratio of pile load and settlement reduction were larger when the offset is from 0.5D to 1.0D than from 1.0D to 1.5D.

• Journal of the Korean Geotechnical Society
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• v.33 no.5
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• pp.37-44
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• 2017

In this study, three dimensional numerical analyses were carried out to predict axial (pullout and compressive) and lateral behavior of rock-socketed steel pipe pile varying diameter, wall thickness, and length. As a result of the pile pullout analyses, it was confirmed that the pullout displacement was inversely proportional to the pile diameter for given pile length, thickness, pullout load. Load-settlement relationship of the compressive pile analyses revealed that the effect of pile thickness on pile resistance was more significant than that of pile diameter. In addition, laterally loaded pile analyses showed that pile lateral resistance is influenced above all else by pile diameter. This study showed that it is necessary to conduct numerical analyses to identify the effects of pile diameter, wall thickness, and pile length on the steel pipe pile behavior as a preliminary pile design under specified loading conditions.

• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.45-57
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• 2008

The improved turnout system is developed to speed-up the pre-existing railroad. The research has been actively carried out far the improved turnout system and the impact factor is estimated using the data sets achieved from the dynamic wheel-load field tests in both the conventional and the improved turnout system. In this study, the track performance and roadbed behavior are examined for the conventional and improved turnout system using the estimated impact factor. Dynamic wheel load and rail pressure are evaluated to assess the track performance. Roadbed stress and settlements are estimated using numerical analysis. Additionally, the stability of roadbed is estimated in soft roadbed condition influenced by the weather effects and cyclic train loading. The results show that dynamic wheel load, rail pressure, roadbed stress, and roadbed settlements in the improved turnout system substantially decrease compared with those in the conventional turnout system.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1065-1072
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• 2010

The excavation site in the new city of inchon songdo is distributed with soft reclaimed soil and marine deposit. So, the general ground anchor is not applied to this layer of soft ground as the earth retaining support system, because of settlement. And then, Jacket pack anchor which is newly developed in order to increasing the pullout resistance by certain grout bulb formation and expansion effect in soft ground is applied to this site instead of the general ground anchor. Though the maximum horizontal displacement shows about 30mm~100mm (The maximum horizontal displacement/excavation depth$\fallingdotseq$0.32~1.0%) according to excavation sequence, generally excavation work finished stably. Also, load cell after setting shows almost increasing trend with increasing horizontal displacement. It means that the settlement of Jacket pack anchor in soft ground is good. From the result of this case, we knew that Jacket pack anchor was able to use the earth retaining support system in soft ground. Using Jacket pack anchor in soft ground, The allowance of the horizontal displacement is applied more than general value considering soil factors.

• Structural Engineering and Mechanics
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• v.52 no.3
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• pp.507-523
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• 2014

Shell foundations have been employed as an alternative for the conventional flat shallow foundations and have proven to provide economical advantage. They have shown considerably improved performance in terms of ultimate capacity and settlement characteristics. However, despite conical shell foundations are frequently used in industry, the theoretical solutions for bearing capacity of these footings are available for only triangular shell strip foundations. The benefits in design aspects can be achieved through theoretical solutions considering shell geometry. The engineering behavior of a conical shell foundation on mixed soils was investigated experimentally and theoretically in this study. The failure mechanism was obtained by conducting laboratory model tests. Based on that, the theoretical solution of bearing capacity was developed and validated with experimental results, in terms of the internal angle of the cone. In comparison to the circular flat foundation, the results show 15% increase of ultimate load and 51% decrease of settlement at an angle of intersection of $120^{\circ}$. Based on the results, the design chart of modified bearing capacity coefficients for conical shell foundation is proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.697-703
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• 2006

In this research, model tests for in-situ Top-Base Foundation are carried out in other to investigate the load delivering mechanism and the incremental effect of bearing capacity. According to the result of model tests, the load-settlement curves of both in-situ Top-Base(In-situ TBF) and Precast Top-Base Foundation(PC-TBF) showed similar results in term of the ground movement and effect of bearing capacity. Also, the range of vertical stresses delivered into ground was decreased with Top-Base method regarding other types foundations.

• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.45-51
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• 2003

This study was undertaken to investigate behavior characteristics of soil-cement piles in composite foundations through computer analysis. The soil-cement piles with cushion subjected to the vertical central loading only were analyzed using the program - “ABAQUS”. The investigation was conducted for various conditions including soil property, pile dimension, replacement ratio, pile/soil modular ratio, and load intensity. The results of analysis provided not only the load transfer and settlement behaviors but also the effective pile length and load distribution between a pile and soil. It was concluded that in the design of composite foundations, the modular ratio and replacement ratio are two design parameters.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.33-40
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• 2008

The load distribution and deformation of rock-socketed drilled shafts subjected to axial loads are evaluated by a load-transfer method. The emphasis is on quantifying the effect of coupled soil resistance in rock-socketed drilled shafts using the 2D elasto-plastic finite element analysis. Slippage and shear load transfer behavior at the pile-soil interface are investigated by using a user-subroutine interface model (FRlC). It is shown that the coupled soil resistance provides the influence of pile toe settlement as the shaft resistance is increased to an ultimate limit state. The results show that the coupling effect is closely related to the value of pile diameter over rock mass modulus (D/$E_{mass}$) and the ratio of total shaft resistance against total applied load ($R_s$/Q). Through comparisons with field case studies, the 2D numerical analysis reseanably presented load transfer of pile and coupling effect due to the transfer of shaft shear loading, and thus represents a significant improvement in the prediction of load deflections of drilled shafts.

• Journal of the Korean Geotechnical Society
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• v.38 no.6
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• pp.5-16
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• 2022

In the case of domestic seismic design, deformation of structures and ground is reviewed through undrained condition analysis and applied to design and maintenance. However, when the ground undergoes dissipation after liquefaction due to a dynamic load such as an earthquake, additional displacement occurs and greater damage occurs. Therefore, it is necessary to additionally analyze the drained conditions, It is necessary to grasp the exact ground behavior such as calculating and reviewing the amount of subsidence of the ground that has undergone the loss process after an earthquake and apply it to design and maintenance together. Therefore, in this study, numerical analysis was performed assuming undrained and drained conditions by dividing pure sandy soil into loose soil with Dr=30% and high-density soil with Dr=70%. In particular, when a dynamic load such as an earthquake is applied, considering the drained conditions of the ground, the settlement amount and the pore water pressure ratio of loose and dense ground are compared, This study focused on comparative analysis of settlement amount and pore water pressure ratio in the process of ground loss after an earthquake. As a result, the amount of subsidence during the dissipation process was 30 to 60 times greater than that of the earthquake.

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.57-67
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• 2013

Micropile technology has evolved continuously since its instruction by Fernando Lizzi in the 1950s. The effects of group micropile have been researched by many researchers. The effects of group micropile differ and change with pile length, pile spacing (S), pile angle (${\theta}$) and pile embedded conditions. In the present study, the effects of resistance increase and settlement reduction from micropiles were investigated through a series of axial load tests. For the study, axial load tests were performed using mat, group micropiles and micropiled-raft (MPR) in various pile spacing and pile angle conditions. As the result, the effects of resistance of micropiled-raft were 80% (3D) to 110% (7D) of the total resistance of mat and group micropile. The effects of settlement restraint of micropiled-raft were 20% (S=3D, ${\theta}=45^{\circ}$) to 70% (7D, ${\theta}=15^{\circ}$) of settlement of mat foundation.