• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.94-110
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• 1994

Types of foundation of high rise buildings are primarily determined by loads transmitted from super structure, soil bearing capacity and available construction technology. The usd of deep foundation cannot be justified due to the fact that rock of enough bearing capacity is not found down until 90 ~ 100m. When a concentration of high soil pressure must be distributed over the entire building area, when small soft soil areas must be bridged, and when compressible strata are located at a shallow depth, mat foundation may be useful in order to have settlement and differential settlement of variable soils be minimized. The concept of mat foundation will also demonstrate some difficulities of applications if the load bearing demand directly carried down to the load -bearing strata exceeds the load -bearing capacity. This paper introduces both the analysis and design of mat type foundation for high rise buildings as well as the methodology of modelling of the soil foundation, especially, engineered to redistribute the stress exceeding the soil bearing capadity. This process will result in the wid spread of stresses over the entire building foundation.

• Journal of Industrial Technology
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• v.25 no.B
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• pp.63-71
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• 2005

This paper is an experimental result of investigating lateral soil movements at piled bridge abutments by using the centrifuge model facility. Three different centrifuge model experiments, changing the methods of ground improvement at bridge abutment on the soft clayey soil (no improvement, preconsolidation and plastic board drains (PBD), sand compaction pile (SCP) + PBD), were carried out to figure out which method is the most appropriate for resisting against the lateral soil movements. In the centrifuge modelling, construction process in field was reconstructed as close as possible. Displacements of abutment model, ground movement, vertical earth pressure, cone resistance after soil improvement and distribution of water content were monitored during and after centrifuge model tests. As results of centrifuge model experiments, preconsolidation method with PBD was found to be the most effective against the lateral soil movement by analyzing results about displacements of abutment model, ground movement and cone resistance. Increase of shear strength by preconsolidation method resulted in increasing the resistance against lateral soil movement effectively although SCP could mobilize the resistance against lateral soil movement. It was also found that installment with PBD beneath the backfill of bridge abutment induced effective drainage of excess pore water pressure during the consolidation by embanking at the back of the abutment and resulted in increasing the shear strength of clay soil foundation and eventually increasing the resistance of lateral soil movement against piles of bridge abutment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.199-210
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• 2012

The effects of tunnelling in weak weathered rock on the behaviour of a pre-existing single pile and pile groups ($3{\times}3$ and $5{\times}5$ pile groups) above a tunnel have been studied by carrying out three-dimensional (3D) elasto-plastic numerical analyses. Numerical modelling of such effects considers the response of the single pile and pile groups in terms of tunnelling-induced ground and pile settlement as well as changes of the shear transfer mechanism at the pile-soil interface due to tunnelling. Due to changes in the relative shear displacement between the pile and the soil at the pile-soil interface with tunnel advancement, the shear stresses and axial pile force distributions along the pile change drastically. Based on the computed results, upward shear stresses are induced up to about Z/L=0.775 from the pile top, while downward shear stresses are mobilised below Z/L=0.775, resulting in a reduction in the axial pile force distribution with depth equivalent to a net increase in the tensile force on the pile. A maximum tensile force of about $0.36P_a$ developed on the single pile solely due to tunnelling, where $P_a$ is the service axial pile loading prior to tunnelling. The degree of interface shear strength mobilisation at the pile-soil interface was found to be a key factor governing pile-soil-tunnelling interaction. Overall it has been found that the larger the number of piles, the greater is the effect of tunnelling on the piles in terms of pile settlement, while changes of the axial pile forces for the piles in the groups are smaller than for a single pile due to the shielding effect. The reduction of apparent allowable pile capacity due to tunnelling-induced pile head settlement was significant, in particular for piles inside the groups.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.1045-1075
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• 2016

Shallow footings are one of the most common types of foundations used to support mid-rise buildings in high risk seismic zones. Recent findings have revealed that the dynamic interaction between the soil, foundation, and the superstructure can influence the seismic response of the building during earthquakes. Accordingly, the properties of a foundation can alter the dynamic characteristics (natural frequency and damping) of the soil-foundation-structure system. In this paper the influence that shallow foundations have on the seismic response of a mid-rise moment resisting building is investigated. For this purpose, a fifteen storey moment resisting frame sitting on shallow footings with different sizes was simulated numerically using ABAQUS software. By adopting a direct calculation method, the numerical model can perform a fully nonlinear time history dynamic analysis to realistically simulate the dynamic behaviour of soil, foundation, and structure under seismic excitations. This three-dimensional numerical model accounts for the nonlinear behaviour of the soil medium and structural elements. Infinite boundary conditions were assigned to the numerical model to simulate free field boundaries, and appropriate contact elements capable of modelling sliding and separation between the foundation and soil elements are also considered. The influence of foundation size on the natural frequency of the system and structural response spectrum was also studied. The numerical results for cases of soil-foundation-structure systems with different sized foundations and fixed base conditions (excluding soil-foundation-structure interaction) in terms of lateral deformations, inter-storey drifts, rocking, and shear force distribution of the structure were then compared. Due to natural period lengthening, there was a significant reduction in the base shears when the size of the foundation was reduced. It was concluded that the size of a shallow foundation influences the dynamic characteristics and the seismic response of the building due to interaction between the soil, foundation, and structure, and therefore design engineer should carefully consider these parameters in order to ensure a safe and cost effective seismic design.

• Journal of the Korean GEO-environmental Society
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• v.10 no.5
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• pp.59-67
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• 2009

Three-dimensional (3D) numerical analyses have been conducted to study the behaviour of a single pile to tunnelling. The numerical analysis has included soil slip at the pile-soil interface. In the numerical analyses the interaction between the tunnel and the pile constructed in weathered soil and rock has been analysed. The study includes the pile settlement, the relative shear displacement between the pile and the soil and the shear stresses at the interface and the axial force on the pile. In particular, the shear stress transfer mechanism at the pile-soil interface related to the tunnel advancement has been rigorously analysed. Due to changes in the relative shear displacement at the pile-soil interface during the tunnel advancement, the shear stress and the axial force distributions along the pile have been changed. Upward shear stress developed at most part of the pile (Z/L=0.0-0.8), while downward shear stress is mobilised near the pile tip (Z/L=0.8-1.0) resulting in tensile force on the pile, where Z is the pile location and L is the pile length. Some insights into the pile behaviour to tunnelling obtained from the numerical analyses will be reported and discussed.

• Earthquakes and Structures
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• v.8 no.5
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• pp.1255-1276
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• 2015

The importance of considering soil-structure interaction effect in the analysis and design of RC frame buildings is increasingly recognized but still not penetrated to the grass root level owing to various complexities involved. It is well established fact that the soil-structure interaction effect considerably influence the design of multi-storey buildings subjected to lateral seismic loads. The shear walls are often provided in such buildings to increase the lateral stability to resist seismic lateral loads. In the present work, the linear soil-structure analysis of a G+5 storey RC shear wall building frame resting on isolated column footings and supported by deformable soil is presented. The finite element modelling and analysis is carried out using ANSYS software under normal loads as well as under seismic loads. Various load combinations are considered as per IS-1893 (Part-1):2002. The interaction analysis is carried out with and without shear wall to investigate the effect of inclusion of shear wall on the total and differential settlements in the footings due to deformations in the soil mass. The frame and soil mass both are considered to behave in linear elastic manner. It is observed that the soil-structure interaction effect causes significant total and differential settlements in the footings. Maximum total settlement in footings occurs under vertical loads and inner footings settle more than outer footings creating a saucer shaped settlement profile of the footings. Each combination of seismic loads causes maximum differential settlement in one or more footings. Presence of shear wall decreases pulling/pushing effect of seismic forces on footings resulting in more stability to the structures.

• Structural Engineering and Mechanics
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• v.57 no.3
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• pp.403-423
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• 2016

The challenges involved with fatigue damage assessment of steel catenary riser (SCR) in the touchdown zone (TDZ) are primarily due to the non-linear behaviour of the SCR-seabed interaction, considerable uncertainty in SCR-seabed interaction modelling and geotechnical parameters. The issue of fatigue damage induced by the cyclic movements of the SCR with the seabed has acquired prominence with the touch down point (TDP) interaction in the TDZ. Therefore, the SCR-seabed response is critical for reliable estimation of fatigue life in the TDZ. Various design approaches pertaining to the lateral pipe-soil resistance model are discussed. These techniques have been applied in the finite element model that can be used to analyse the lateral SCR-seabed interaction under hydrodynamic loading. This study investigates the sensitivity of fatigue performance to geotechnical parameters through a parametric study. In this study, global analyses are performed to assess the influence of vertical linear seabed springs, the lateral seabed model and the non-linear seabed model, including trench evolution into seabed, seabed normalised stiffness, re-penetration offset parameter and soil suction resistance ratio, on the fatigue life of SCRs in the TDZ.

• Economic and Environmental Geology
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• v.37 no.1
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• pp.61-72
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• 2004

The soil samples were collected from the paddy field near the mine tailing dumps in the abandoned Duckum mine in Korea. In the laboratory, the soil solution was extracted from the soil using centrifuge, and analysed for the chemical composition. Physical and chemical soil properties were also analysed. Kaolinite is the main clay minerals in the paddy soil and the CEC value is therefore relatively low. Nearly all soil samples show enrichment in their trace elemental concentrations(Cd, Cu, Pb and Zn) compared with natural background level. Some soil samples exceed the soil remediation intervention values for Cd, Pb and Zn and target value for Cu, when compared with Dutch standard, whereas As, Ni and Cr are in normal range. Lead concentrations in some samples near the mine tailing dumps also exceed the standard for remediation act for agricultural area set by Korean soil conservation law. The trace elemental concentrations are higher in the paddy soil nearer the mine tailing dumps and lower for the samples from distance. Similar trend with distance is found for the soil solution chemistry but the decrease with distance from the mine tailing dumps are sharper than the changes in soil chemistry. Cadmium, Cu and Pb concentrations in the soil solution are very low, ranging from a tenth and hundredths to a maximum of several mg/l, whereas their concentrations in soils are highly enriched for natural background. Most of the trace elements are thought to be either removed by reduced iron sulphides or iron oxides, depending on the redox changes. Geochemical equilibrium modelling indicate the presence of solubility controlling solid phases for Cd and Pb, whereas Zn and Cu might have been controlled by adsorption/desorption processes. Although pollutants migration through solution phase are thought to be limited by adsorption onto various Fe, Mn solid phases, the pollutants exist as easily releasable fractions such as exchangeable site. In this case, the paddy soil would act as pollutant pool, which will supply to plants in situ. whenever the geochemical conditions favour.

• Journal of the Korean GEO-environmental Society
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• v.11 no.1
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• pp.27-34
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• 2010

A finite element analysis has been conducted to clarify the behaviour of a single pile in heaving ground related to ground excavation. The numerical analysis has included soil slip at the pile-soil interface, analysing the interaction between the pile and the clay has been studied. The study includes the upward movement of the pile, the relative shear displacement between the pile and the soil and the shear stresses at the interface and the axial force on the pile. In particular, the shear stress transfer mechanism at the pile-soil interface related to a decrease in the vertical soil stress has been rigorously analysed. Due to the reductions in the vertical soil stress after excavation, the relative shear displacement and the shear stress along the pile have been changed. Upward shear stress developed at most part of the pile (Z/L=0.0-0.8), while downward shear stress is mobilized near the pile tip (Z/L=0.8-1.0) resulting in tensile force on the pile, where Z is the pile location and L is the pile length. Some insights into the pile behaviour in heaving ground analysed from the numerical analyses has been reported.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.121-126
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• 2005

It is not uncommon to observe tilt of buildings and towers as a result of unexpected differential foundation settlements. Over the years, a number of engineering methods including the soil extraction technique have been attempted to reduce inclination of buildings and towers. In this research, a series of novel geotechnical centrifuge model tests by using a state-of-the-art in-flit robotic manipulator have been conducted to study key factors which govern the restoration of building tilts. In the centrifuge model tests, the robotic manipulator was used to drill and extract soil in-flight near an initially tilted model building. The soil extraction was to induce stress release, thereby mitigating the inclination of the model building. Insights into the effects of different configurations, soil density and sequences of drilling observed during the centrifuge model tests on the restoration of the model building are to be investigated.