• Geotechnical Engineering
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• v.13 no.4
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• pp.37-54
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• 1997

This paper is to investigate the bearing capacity and the failure mechanism of slope subjected to strip surcharges adjassent to embankment slope of sandy soil. Parametric model tests under plain strain condition were performed by changing width of footing, relative density of slope materials, and position of footing from the crest of slopes. For model tests, Jumunjin standard sand was used as the slope material and its relative density was 45% and 70%, respectively. The angle of slope was formed with 1 : 1.5 and 1 2. Rigid model footings, made of aluminuu were used with their widths of 4, 7, 10 and 12cm. For the position of model footing, position ratios, distance of model footing from the crest of slope divided by footing width, were 0, 0.5, 1, 2, 3, 4, 5. Failure mechanism was observed by using ink colored sands and markers inserted in model slopes. Ultimate bearing capacity obtained from tests was analyzed and compared with limit equilibrium method, limit analysis method and empirical equation. Characteristics of load-settlement curves and failure mechanism were also analyzed and compared with the existing theories. Thus, their effects on ultimate bearing capacity of model footing adjacent to slope were assessed.

• Journal of the Korean GEO-environmental Society
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• v.17 no.1
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• pp.49-54
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• 2016

An active layer distributed on surface of an extreme cold region causes a frost heave by repeating the freezing and thawing according to the seasonal temperature change. Since the height of frost heave is greatly affected by the thickness of active layer, an accurate evaluation of the thickness of active layer is necessary for the safe design and construction of the infrastructure in the extreme cold region. In this study, dynamic cone penetrometer, which is miniaturized in-situ penetration device, is applied for the evaluation of active layer depth distribution. As the application tests, two dynamic cone penetration tests were conducted on the study sites located in Solomon and Alaska. In addition, ground temperature variations were obtained. As the results of the application tests, the depth of interface between the active layer and the permafrost was evaluated from the difference in dynamic cone penetration indexes of the active layer and the permafrost, and a layer was detected around the interface considered as an ice lens layer. Also, the interface depths between the above zero and the below zero temperature determined from the ground temperature variations correspond with the interface depths evaluated from the dynamic cone penetration tests. This study demonstrates that the dynamic cone penetrometer may be a useful tool for the evaluation of the active layer in the extreme cold region.

• Journal of the Korean Geosynthetics Society
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• v.18 no.3
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• pp.33-44
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• 2019

Clinker layer is a stratum structure distributed in volcanic area such as Jeju Island. The clinker layers were formed in between the repetitive action of eruption and solidification of lava flows. Since the clinker layer contains a large amount of voids accompanied by the lava gas ejection process, there is a possibility of inducing overall stability of the ground due to the low stiffness and strength of the clinker layer. Therefore, in this study, site investigation was carried out at both ends of the 00 bridge where the clinker layers exist. And, based on the ground survey results, the behavior of shallow foundations was analyzed numerically. In addition, the improved shallow foundation behavior in grouting substitution using the chemical injection method of the clinker layer was compared with the shallow foundation behavior in the ground, and the grouting substitution efficiency of each layer was analyzed. As a result, the bearing capacity, the replacement efficiency and elastic settlement were different according to the presence or absence of the sediment layer. This is because the sediment layer has a lower stiffness and density than the clinker layer.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.5-13
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• 2007

The performance of innovative prestressed support (IPS) earth retention system applied in soft clay was investigated and presented. The IPS wale system provides a high flexural stiffness to resist the bending by lateral earth pressure, and transfers lateral earth pressure to strut supports. The IPS wale system provides a larger spacing of support than conventional braced and anchored systems. The IPS earth retention system was selected for temporary earth support in a building construction in North Busan area. The excavation was made 28.8 m wide, 52.0 m long, and 16.1 m deep through loose fill to soft clay. The IPS system consists of 650 mm thick slurry walls, and five levels of IPS wales and struts. Field monitoring data were collected including wall deflections at six locations, ground water levels at four locations, IPS wale deflections at thirty locations, and axial loads on struts at twenty locations, during construction. The IPS earth retention system applied in soft clay performed successfully within a designed criterion. Field measurements were compared with design assumptions of the IPS earth retention system. The applicability and stability of the IPS earth retention system in soft clay were investigated and evaluated.

• Journal of the Korean Geotechnical Society
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• v.23 no.12
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• pp.33-42
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• 2007

The assessment of shear wave velocity($V_s$) in soft soils is extremely difficult due to the soil disturbances during sampling and field access. After a ring type field $V_s$ probe(FVP) has been developed, it has been applied at the southern coastal area of the Korean peninsular. This study presents the upgraded FVP "blade type FVP", which minimizes soil disturbance during penetration. Design concerns of the blade type FVP include the tip shape, soil disturbance, transducers, protection of the cables, and the electromagnetic coupling between transducers and cables. The cross-talking between cables is removed by grouping and extra grounding of the cables. The shear wave velocity of the FVP is simply calculated by using the travel distance and the first arrival time. The large calibration chamber tests are carried out to investigate the disturbance effect due to the penetration of FVP blade and the validity of the shear waves measured by the FVP. The blade type FVP is tested in soils up to 30m in depth. The shear wave velocity is measured every 10cm. This study suggests that the upgraded blade type FVP may be an effective device for measuring the shear wave velocity with minimized soil disturbance in the field.

• Journal of the Korean Geotechnical Society
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• v.23 no.12
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• pp.83-94
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• 2007

Piled raft foundations have been highlighted as an economical design concept of pile foundations in recent years. However, piled raft foundations have not been widely used in Korea due to the difficulty in estimating the complex interaction effects among rafts, piles and soils. The authors developed an effective numerical program to analyze the behavior of piled raft foundations for practical design purposes and presented it briefly in this paper. The developed numerical program simulates the raft as a flexible plate consisting of finite elements with eight nodes and the raft is supported by a series of elastic springs representing subsoils and piles. This study imported another model to simulate pile groups considering non-linear behavior and interaction effects. The apparent stiffnesses of the soils and piles were estimated by iterative calculations to satisfy the compatibility between those two components and the behavior of piled raft foundations can be predicted using these stiffnesses. For the verification of the program, the analysis results about some example problems were compared with those of rigorous three dimensional finite element analysis and other approximate analysis methods. It was found that the program can analyze non-linear behaviors and interaction effects efficiently in multi-layered soils and has sufficient capabilities for application to practical analysis and design of piled raft foundations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.87-94
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• 2019

Recently, the advance of accurate dynamic displacement measurement devices, such as GPS, computer vision, and optic laser sensor, has enhanced the structural monitoring technology. In this study, the dynamic displacement data was used to verify the applicability of the structural physical parameter estimation method through subspace system identification. The subspace system identification theory for estimating state-space model from measured data and physics-based interpretation for deriving the physical parameter of the estimated system are presented. Three-degree-freedom steel structures were fabricated for the experimental verification of the theory in this study. Laser displacement sensor and accelerometer were used to measure the displacement data of each floor and the acceleration data of the shaking table. Discrete state-space model generated from measured data was verified for precision. The discrete state-space model generated from the measured data extracted the floor stiffness of the building after accuracy verification. In addition, based on the story stiffness extracted from the state space model, five column stiffening and damage samples were set up to extract the change rate of story stiffness for each sample. As a result, in case of reinforcement and damage under the same condition, the stiffness change showed a high matching rate.

• Geotechnical Engineering
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• v.12 no.6
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• pp.185-198
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• 1996

EPS is increasingly used as a filling material in soft ground. The beneficial effects of the use of EPS derive from minimizing the stress increment, which, in turn, increases the bearing capacity and reduces the settlement. EPS can also be used as a backfill material for retaining walls and abutments to reduce the horizontal earth pressure. However, there is no rational application for the selection of the EPS fill which is essential to the selection of the filling configuration and the settlement calculation. In this paper, therefore, the nonlinear numerical model developed from the results of triaxial compression tests is applied to the construction of EPS and verified through the comparison between the prediction and in-situ measurements.

• Geotechnical Engineering
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• v.12 no.6
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• pp.163-184
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• 1996

In this study, physical and geotechnical properties of the light weight mixed soil( weathered granite soil mixed with small pieces of waste EPS) were analyzed by laboratory experiments to examine its suitability for backfill materials of the reinforced-earth walls. Friction characteristics of geogrid-light weight sized soil were also investigated by performing the pullout tests for two types of geogrids having different flexural rigidity. Also a procedure was proposed to evaluate friction strength between geogrid and light weight miffed soil by using a stress-strain relationship of the orthotropic composite material subjected to both longitudinal and vertical loadings. By the procedure proposed in this study, values of the calibration coefficients ul and uf applicable for the evaluation of friction strengths between two types of geogrids and light weight mixed soils were further presented.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.217-224
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• 1999

This Paper shows the results of a series of model tests on the behavior of single rigid Pile, which subjected to lateral load, in non-homogeneous Nak-Dong River sands, consisted of two layers, upper and lower layers. The purpose of the present paper is to investigate the effect of ratio of lower layer thickness to embedded pile length ratio of soil modules of upper to lower layer (E$\sub$h1//E$\sub$h2/) and pile head constraint condition on the characteristics of lateral behavior of single pile. These effects can be quantified only by the results of model tests. As a model test result, in non-homogeneous sand, it shows that the lateral behavior depends upon the ratio of soil modules of upper to lower layer more than other factors. And, in respect of deflection, it was found that the reduction ratio of deflection by pile head fixity is the value of 0.5 and 0.6 for E$\sub$h1//E$\sub$h2/=0.18 and E$\sub$h1//E$\sub$h2/=5.56, respectively. The critical thickness of lower layer on the change of deflection is about 25 - 50% of pile embedded length. Also, in respect of maximum bending moment it was found that the reduction ratio of maximum bending moment by pile head fixity is the value of 0.55 and 0.7 for E$\sub$h1//E$\sub$h2/=0.18 and E$\sub$h1//E$\sub$h2/=5.56, respectively.