• Journal of the Korean GEO-environmental Society
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• v.21 no.8
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• pp.15-27
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• 2020

In the current paper, a series of advanced 3D finite element analyses have been performed on existing pieces of work of negative skin friction from a geotechnical centrifuge test and full-scale field measurements. From these analyses, key features of pile behaviour under the influence of negative skin friction which, previously, were not fully understood in existing studies, have been meticulously discussed. As such, it has been possible to successfully address several numerical modelling issues such as negative skin friction induced pile settlements and group effects (the shielding effect), the effect of sacrificial piles in groups and the interaction between the pile head and the cap, the effect of interface elements at the pile-soil interface and the time-dependent pile behaviour. During a geotechnical centrifuge test, substantial amounts of negative skin frictions were mobilised when centrifugal acceleration increased from 1g to a certain g-level due to an increase in the self-weight of soil. The behaviour of piles inside a group were heavily affected by the sacrificial piles and the connectivity between the pile head and the pile cap. In particular, as negative skin friction has time dependent qualities associated with consolidation, it was logical to perform coupled analyses when analysing piles in consolidating grounds. From the current work, several insufficiencies of previous researches have been addressed, and the engineering pile behaviour subjected to negative skin friction has been clarified.

• Journal of the Korean Institute of Landscape Architecture
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• v.44 no.1
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• pp.93-106
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• 2016

This study aimed to estimate and evaluate the thermal mitigation of the urban tree canopy on the summer outdoor environment by quantitative use of mean radiant temperature. This study applied the SOLWEIG model based $T_{mrt}$ comparison method by using both (1) urban tree canopy presence examples and (2) urban tree canopy absence examples as constructed from airborne LiDAR system based three-dimensional point cloud data. As a result, it was found that an urban tree canopy can provide a decrease in the entire domain averaged daily mean $T_{mrt}$ about $5^{\circ}C$ and that the difference can increase up to $33^{\circ}C$ depending both on sun position and site conditions. These results will enhance urban microclimate studies such as indices (e.g., wind speed, humidity, air temperature) and biometeorology (e.g., perceived temperature) and will be used to support forest based public green policy development.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.1
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• pp.164-172
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• 2010

The objective of this research is to assess the level of urban park service provision in comparison to demand population size by region (e.g., dong) in Busan metropolitan areas. To this end, a park service provision assessment index is utilized. The index is built upon the difference between planned and actual levels of park service provision. For each region, planned level is obtained by multiplying the per capita service amount by the number of residents in that region. Actual level is estimated based on Huff model, where distance between parks and residential locations are explicitly accounted for in model building. Empirical analysis was carried out for Busan Metropolitan Area. The result shows that Gumsung-dong, Chunga-dong and Dongdaesin3-dong are well supplied with park service, while Hadan1-dong, Goejung2-dong and Joorae3-dong are under-provided when per capita service provision amount and the extent of service area are set to $6m^2$ and 1km, respectively. It is argued that those regions that suffer from under-provision need to be highlighted such that a priority is given to those areas for establishing new urban parks when renewing urban management plan.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.47-56
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• 2001

In the present study, mainly to determine the embarkation time of equipment in dredged clay fills, an analytical approach is performed to predict a variation of the undrained shear strength in the outermost layer. In this approach, Gibson's non-dimensional linear constant defining the relationship between the void ratio and the effective stress is employed. Also in this approach, void ratios and settlements associated with the volume change due to the self-consolidation and the desiccation shrinkage are evaluated at various elapsed times based on the finite difference solution technique proposed by the authors(1999) and the developed computer program named as DSCON. Predicted results(water content ratio, unit weight and undrained shear strength) are compared with those of laboratory model tests conducted with soil samples obtained from the Koheung site. Based on the predicted undrained shear strengths, possible embarkation time of a equipment is also evaluated. In addition, further analyses are made to indirectly verify the efficiency of the analytical approach proposed in the present study using the PSDDF computer program which can consider the drainage efficiency.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.149-157
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• 2005

In cases of the loosely accumulated ground and soft clayey soils, the settlement criterion usually governs in evaluating the stability of structures. The settlement is also a dominant factor to control the design of granular compaction piles mainly applied to the reinforcement of foundation structures in soft ground. In the previous studies, settlement behaviors of granular compaction piles have generally been analyzed with an evaluation of the settlement reduction factor based on the load-sharing ratio and the replacement ratio. In this approach, however, since the reinforced ground with granular compaction piles is simplified as the composite ground, only the difference of a relative vertical strength between piles and soils is taken into account without reflecting lateral behaviors of granular compaction piles. In the present study, the method of estimating the settlement of granular compaction piles is proposed by synthetically considering a vertical strength of the ground, lateral behaviors of granular compaction piles, the strength of pile materials, a pile diameter, and an installation distance of the pile. Further, far the verification of a validity of the proposed method, predicted settlements are compared with results from previous studies. In addition, parametric studies are performed together with detailed analyses of relevant design parameters.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.159-168
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• 2005

In the previous studies, settlement behaviors of granular compaction piles have generally been analyzed with an evaluation of the settlement reduction factor based on tile load-sharing ratio and the replacement ratio. In this approach, however, since the reinforced ground with granular compaction piles is simplified as the composite ground, only the difference of a relative vertical strength between piles and soils is taken into account without reflecting lateral behaviors of granular compaction piles. In the companion research paper, the method of estimating the settlement of granular compaction piles was proposed by synthetically considering a vertical strength of the ground, lateral behaviors of granular compaction piles, the strength of pile materials, a pile diameter, and an installation distance of the pile. In the presented study, to validate a propriety of the previously proposed method, large scale field load tests and three dimensional numerical analyses are performed. The results are analyzed in detail and compared with the predicted settlements by the proposed method. Finally, a simple method to estimate the settlement of granular compaction piles is suggested for an easy application of the practical design.

• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.99-114
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• 2005

In Part I of this paper, a conceptual approach of the stress path method was newly proposed for a rational estimation of settlements of saturated clay deposits. A detailed procedure for effective evaluation and use of settlement-related characteristic deformation behaviors was developed in order to provide practicality to the new approach. In this Part II, on the basis of the results of Part 1, the concept of the new approach was embodied in the form of a detailed settlement estimation procedure. The applicability and usefulness of the new procedure were strongly supported by various application examples. In addition, possible errors of other conventional settlement estimation methods were investigated by comparing with the new procedure. Because of its flexible applicability for wide range of field conditions, the new procedure will have great usefulness in the practical side. For example, a reasonable foundation design based on allowable settlement criteria can be easily performed and modification of design factors can be readily reflected even during the subsequent construction stage. Especially, the new procedure will be of great use for preliminary work in a large scale construction site where various structures are planned to be constructed on a nearly identical ground condition.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.295-307
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• 2002

In the Nakdong River plain a very thick clayey soils are covered widely. Since the early 1990's, some huge reclamation projects have been performed for the development of industrial and residential complexes and so on. Despite a large number of soil investigations have been carried out for the projects, the geotechnical properties have never been elucidated well, so that the settlements of the ground due to the mischaracterized properties were greatly underestimated. Therefore, it has been needed to evaluate definitely the characteristics of the clayey soils, particularly for the compressibility characteristics to help understand the settlement behavior. For the compressibility characteristics of the Pusan clays, physical index and consolidation tests were conducted on the reconstituted and undisturbed samples. Using the result of physical index, the Pusan clays could be divided into two different units, which have different depositional environments. According to the concepts of Burland (1990) and Nagaraj et. al. (1990), the intrinsic state line and field compression curve of the Pusan clays could be established. It could be found from their concepts that the Pusan clays are under the cemented and young normally consolidated state and largely consisted of two units. The cementation of the clays was as well identified by compression index ratio (Tsuchida et. al.,1991) and sensitivity (Leroueil et. al.,1983).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.141-150
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• 1987

The Soyanggang Dam completed in 1973 was well instrumented during construction period. The measured results for stresses and movements of the embankment have already been published elsewhere, but theoretical analyses have not been made until now. This study intends to analyze the stress and deformation behavior of the embankment numerically which have been subjected to the load of materials during construction and water load during impounding. The constitutive law used for the analyses is hyperbolic model developed by Duncan et al., and a nonlinear incremental finite element analysis simulating its contruction steps is. used in this study. Hyperbolic parameters for each Zone are estimated from literature. The results obtained from the theoretical analyses clearly show deformation characteristics and stress vectors in arbitrary section of the dam. The analytical results ate well agreed with the measured deformations at the maximum cross section, however, there are some discrepancy in horizontal movements and in stresses generated in the core zone. From the numerical analyses and its comparison with the measured values, it is charaterized that relatively large construction settlements occurred in core zone, overburden pressure in the core zone was considerably reduced by arching effect, and tension zones might occur near both abutments because of the large horizontal displacement.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.90-97
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• 2019

In recent years, flood due to the consecutive storm events have been occurred and property damage and casualties are in increasing trend. This study calls the consecutively occurred storm events as a mega rainfall scenario and the discharge by the scenario is defined as a mega flood discharge. A mega rainfall scenario was created on the assumption that 100-year frequency rainfall events were consecutively occurred in the Gyeongancheon stream basin. The SSARR (Streamflow Synthesis and Reservoir Regulation) model was used to estimate the mega flood discharge using the scenario in the basin. In addition, in order to perform more reasonable runoff analysis, the parameters were estimated using the SCE_UA algorithm. Also, the calibration and verification were performed using the objective functions of the weighted sum of squared of residual(WSSR), which is advantageous for the peak discharge simulation and sum of squared of residual(SSR). As a result, the mega flood discharge due to the continuous occurrence of 100-year frequency rainfall events in the Gyeongan Stream Basin was estimated to be 4,802㎥/s, and the flood discharge due to the 100-year frequency single rainfall event estimated by "the Master Plan for the Gyeongancheon Stream Improvement" (2011) was 3,810㎥/s. Therefore, the mega flood discharge was found to increase about 992㎥/s more than the single flood event. The results of this study can be used as a basic data for Comprehensive Flood Control Plan of the Gyeongan Stream basin.