• Journal of the Korean GEO-environmental Society
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• v.18 no.5
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• pp.5-16
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• 2017

In the present work, a number of advanced three-dimensional (3D) parametric finite element numerical analyses have been conducted to study the behaviour of a single pile in consolidating ground from coupled consolidation analyses. A single pile with typical minimum and maximum ranges of fill height and clay stiffness has been modelled. The computed results demonstrate that the higher the height of the fill above the clay surface and the smaller the stiffness of the clay, the higher the dragloads and the negative skin friction-induced pile settlements. It has been found that the development of dragloads and pile settlement is more governed by the stiffness of the clay rather than the height of the fill. Positive shaft resistance is mobilised only after the average degree of consolidation is larger than 50%. Although the pile is installed when the degree of consolidation is 50% or more, relatively large negative skin friction can nevertheless develop on the pile. On the other hand, when a load is applied on the pile experiencing an increase in the negative skin friction with time during consolidation, the pile undergoes a large increase in the final settlement of up to 95% compared to that of a pile without axial load on the pile head. The allowable pile capacity when there is negative skin friction on the pile is reduced by about 4-11% compared to a pile without negative skin friction.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.5
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• pp.62-70
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• 2016

Ensuring walkability in a city where pedestrians and vehicles coexist is an issue of critical importance. The relative relationship between vehicle transit and walkability improvements complicates the evaluation of walkability, which thus necessitates the formation of a quantitative standard by which a methodological measurement of walkability can be achieved inside the pedestrian network. Therefore, a model is determined whereby quantitative indices such as, but not limited to, experiences of accessibility, mobility, and convenience within the network are estimated. This research proposes the integration of space syntax theory and the logit path choice model in the evaluation of walkability. Space syntax theory assesses adequacy of the constructed pedestrian network through calculation of the link integration value, while the logit model estimates its safety, mobility, and accessibility using probability. The advantage of the integrated model hence lies in its ability to sufficiently reflect such evaluation measures as the integration value, mobility convenience, accessibility potential, and safety experienced by the demand in a quantitative manner through probability computation. In this research, the Dial Algorithm is used to arrive at a solution to the logit model. This process requires that the physical distance of the pedestrian network and the perceptive distance of space syntax theory be made equivalent. In this, the research makes use of network expansion to reflect wait times. The evaluation index calculated through the integrated model is reviewed and using the results of this sample network, the applicability of the model is assessed.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.5
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• pp.12-19
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• 2016

An average of 20 million individual transit unit activities per day on the Seoul-Gyeonggi-Incheon public transportation network are provided as transportation card analysis data by the metropolitan district (99.02% by 2014 standard, Humanlive, 2015.4). The metropolitan transportation card data can be employed in a comprehensive analysis of public transportation users' current transit patterns and by means of this, an effective use plan can be explored. In enhancing the existing information on the bus and rail integrated network of the metropolis with public transportation card data, the constraints in the existing methodology of metropolitan transit analysis, which functions on a zone unit origin and destination basis, can be overcome. Framework for metropolitan public transportation card data based integrated public transportation analysis, which consists of bus and rail integrated transport modes, is constructed, and through this, a single passenger's transit behavior transit volume can be approximated. This research proposes that in the use of metropolitan public transportation card data, integrated public transportation usage, as a part of individual passenger spatial movements, can be analyzed. Furthermore, metropolitan public transportation card usage data can provide insights into understanding not only movements of populations taking on transit activities, but also, characteristics of metropolitan local space.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.363-369
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• 2003

The purpose of this study is to understand the dissipation pattern of excess pore pressure after liquefaction and to estimate the variation in permeability during shaking load, which should be known for settlement predictions of the ground undergoing liquefaction. In this study, 1-g shaking table tests were carried out for 5 different kinds of sands, all of which had high liquefaction potentials. During the tests excess pore pressure at various depths, and surface settlements were measured. The measured dissipation curve of the excess pore pressure after liquefaction was linearly simulated using the solidification theory, and from the analysis of the slopes of linearly simulated curves, the correlation between dissipation velocity and the gradation characteristics was obtained. By substituting this correlation and the measured settlement to the dissipation velocity equation recommended in solidification theory, the permeability during dissipation was calculated, which was used for estimating the permeability variation during shaking load. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size divided by the coefficient of uniformity. The permeability during dissipation and liquefaction increased by 1.1∼2.8 times and 1.4∼5 times compared to the initial permeability of the original ground, respectively. And the amount of increase became greater as the effective grain size of the test sand increased and the coefficient of uniformity decreased.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.387-395
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• 2003

Model tests were conducted to study the behavior of the piled raft foundation system on sands. Especially in this study, the method using the triaxial compression apparatus was devised and used to apply the confining pressure which is considered difficult in the existing model test on the soil. Steel rods (6mm dia.) and aluminum plates (8mm thickness, 50mm dia.) were used to simulate piles and rafts respectively. Jumunjin standard sands were used to ensure the homogeneity of the sample. After the sample with the piled raft model was laid inside the triaxial cell, the confining pressure was applied and then the compressive force was applied. The increase and/or decrease ratio of the bearing capacity, the load distribution ratio between raft and piles and the effect of settlements decrease depending on the confining pressure, the number of piles and the length of piles were analyzed and the bearing capacity and skin friction of the pile was calculated. By the results of these experiments, the bearing capacity increased and the settlement decreased with this piled raft foundation system. Especially the effect was larger with the increase of the number of piles than with the increase of length of piles. Hereafter, the study of the load transfer mechanism of piles under confining pressure would be made possible using these small model tester like triaxial compression apparatus.

• Spatial Information Research
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• v.21 no.2
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• pp.35-43
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• 2013

The aim of this research is to analyze the priority to functions of the U-city Service Aid Organization(USAO), which is to support invigorating U-City industry. This research analyzes the relative importance and the priority about the functional area and components of UASO based on AHP. This research also performs a sensitivity analysis. The research result shows that relative importance of functional area is like following orders: 1) distribution of U-City service-related information, 2) quality certification of U-City-related products and services, 3) R&D of U-City technology, 4) standardization of U-City, 5) U-City human resource development. The relative importance order of functional components is 1) establishment of U-City information distribution organization, 2) construction and management of U-City information distribution network, 3) supporting U-City information distribution and price policy, 4) providing U-City information list for distribution, 5) preparation and application of quality certification standard of U-City products and services, 6) research on legal system of U-City items, targets, and procedures for quality certification, 7) research, analysis, and provision of U-City information distribution situation, 8) level examination of constructed infrastructures and services in U-City, 9) U-City core technology development and localization of technology, 10) standardization of collected U-City information, service classification, distribution system. This research result can be applied directly to design functions of USAO. The result also can be used for duty management, human resource planning, or resource allocation.

• Journal of the Korean GEO-environmental Society
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• v.4 no.3
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• pp.27-40
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• 2003

In the present study, a newly modified soil nailing technology named as the PSN(Pretension Soil Nailing) system is proposed. Effects of various factors related to the design of the pretension soil nailing system, such as the length of a sheathing pipe and the fixed cone, are examined throughout a series of the displacement-controlled field pull-out tests. 9 displacement-controlled field pull-out tests are performed in the present study and the pretension forces are also evaluated based on the measurements. In addition, both short-term and long-term characteristics of pull-out deformations of the newly proposed PSN system are analyzed and compared with those of the general soil nailing system by carrying out the stress-controlled field pull-out tests. A numerical approach is further made to determine a postulated failure surface as well as a minimum safety factors of the proposed PSN system using the shear strength reduction technique and the $FLAC^{2D}$ program. Global minimum safety factors and local safety factors at various excavation stages computed in case of the PSN system are analyzed throughout comparisons with the results expected in case of the general soil nailing system. An efficiency of the PSN system is also dealt with by analyzing the wall-facing deformations and the adjacent ground surface settlements.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.4
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• pp.33-43
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• 2016

Public transportation card data, which is collected for purposes of the Integrated Public Transportation Fare System, provides neither transfer time nor transfer frequency occurring on the metropolitan city-rail (MCR). And because there are no transfer toll gates installed on the MCR, data on transfers between lines are estimated through means such as elicitations using survey questionnaire, or otherwise through macroscopic observations, which poses the risk of transfer time and frequencies being underestimated. For the accurate estimation thereof, an explanation of the transit path that arises between the Entry-and Exit-Gates must be provided. The purpose of this research is twofold : 1) to build a transit path model to reflect the current state of transfer movements on the basis of transportation card reader data, and 2) to deduce information on transfers occurring in the greater metropolis. To achieve these aims, the idea of Big Nodes is introduced in the model to align transportation card reader operation system characteristics with those of the MCR network. The link-label method is applied in the model as well to make certain that the MCR network runs in an effective manner. Administrative information obtained by the transportation card reader is used to derive transfer time and frequency both in the city's mid-zones, and in the Seoul-Gyeonggi-Incheon district's large-zones. Public transportation card data from a single specific day in year 2014 is employed in the building of the quantified transfer specific data. Extended usage thereof as providing comprehensive data of transfer resistance on the MCR is also examined.

• Korean Security Journal
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• no.19
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• pp.187-205
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• 2009

In this study, Horgan(2005)'s argument highlights the centrality to any successful counter-terrorism strategy of understanding the social context in which terrorist ideologies take root. Counter-terrorism refers to the practices, tactics, techniques, and strategies that governments, militaries, police departments and corporations adopt in response to terrorist threats and/or acts, both real and imputed. Pickering et al.(2008) historically explained four counter-terrorism strategies as traditional counter-terrorism model, community intelligence model, belonging model, social cohesion model. It is thus proposed that counter-terrorism strategies are based in established networks within the community and proactively seeks to continually renew these relationships between the community and police. This approach must embrace an explicit recognition of multiculturalism and its political imperative and drive in a policing organization explicitly committed to social cohesion and human rights in both discourse and practice. We, therefore, suggests community tree counter-terrorism approaches, or community intelligence model, belonging model and social cohesion model to apply to counter-terrorism agencies in Korea. These models are on the basis of Pickering et al.'s counter-terrorism models, which by using community policing to boot socially cohesion police are better able to position themselves as mediators to negotiate settlements between the competing demands of different social groups.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.197-206
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• 2004

The ground anchor support system may not be occasionally used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in the upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing), is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the PSN system. Also, proposed are techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear, Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors are analyzed. In addition, effects of the reduction of deformations expected by pretension of the soil nails are examined in detail throughout an illustrative example and the $FLAC^{2D}$ program analysis. And a numerical approach is proposed PSN system using the shear strength reduction technique with the $FLAC^{2D}$ program.