• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.21-34
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• 2014

This paper studies the time-dependent behaviors of tunnel and surrounding ground due to tunnel deterioration. In the first part, the literature on deterioration characteristics of tunnels was reviewed. In the second part, a numerical analysis was performed to investigate the behavior of concrete lining on the typical section of Korean high-speed rail tunnel (weathered rock) after determination of input variables related to deterioration impact. The result shows that the settlement at the crown of tunnel and surface ground increased up to 7.0% and 30.2% of the total settlements during construction stage, respectively, and the internal convergence reduction of 9.0 mm for concrete linings was generated within 30 years after completion of tunnel construction. Also the loosening height increased up to 2.55 times of tunnel height within 50 years, which is higher than that of Terzaghi's recommendation on ultimate state. Due to this process of extending zones, it is found that additional loads were applied to concrete lining with the axial stress about 3.20~3.66 MPa, which accelerates tunnel deterioration. Finally the quantitative design approach to evaluate time-dependent behavior of lining and surrounding ground due to tunnel deterioration was proposed.

• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.148-161
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• 2018

A traffic fatality by young people marked average annual decrease of 4.5% since 2011. Meanwhile, a traffic fatality by senior over 65 years old marked average annual increase of 7.9% for the last five years which means that the annual increase of traffic fatality by senior will be a serious problem. This study started questioning that senior drivers over 65 years old did not retain the same causal factor of fatal traffic accidents and thus extensively analyzed a risk of it by age group quantitatively, dividing the senior driver group into the early, middle and latter stages. Depending on the aging level, the risk of traffic fatality showed a wide difference in seven different types of traffic accidents generally, and happened to increase with latter and middle parts of the senior driver more than the early part. Therefore, this study proposes four policy suggestions: 1) The senior driver need to be offered customized driving educations and the improvement of road environment is also recommended. 2) Political assistance is needed to support and guide a safety related technology installation for the new or existing car. 3) Renewal of driving license and an aptitude test(physical examination, cognitive test) for drivers over 75 years old should take in a less than 3 years and an additional road test is needed as occasion demands. 4) Like the United States and Europe, development and extension of customized treatment guidebook for medical teams who examine senior drivers is needed and establishment of education and administration system that a supervisor of driving license renewal can impose safety restriction and American anonymity reporting system is considered to institutionalize in the medium to longer term.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.5
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• pp.799-812
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• 2017

Backfill grouting and realistic convergence distribution were not properly considered in previous studies on 2D numerical analysis of a shield TBM tunnel. In this study, a modeling method was suggested to cope with this problem by considering a realistic convergence distribution and proper properties of backfill grouting. To this end, the influence of gap parameter and depth of rock cover on volume loss and composed of ground volume loss around tunnel excavation and surface volume loss were analyzed with a single layer of weathered soil. As a result, most of surface settlements were occurred immediately after excavation. Additional, as depth of rock cover and gap parameter increased, the influence range of surface settlement curves obtained from 2D numerical analyses became broader than a suggested theoretical equation. Therefore, it is inferred that gap parameter should be applied based on load distribution ratio and the property of backfill grouting properly considered for the estimation of the precise behavior of a shield TBM tunnel in 2D numerical analysis.

• Korean Journal of Remote Sensing
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• v.22 no.5
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• pp.313-323
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• 2006

Forest Canopy Density is a dynamic process mediated by various natural and anthropogenic factors. It can be changed over time and locations in the same forest type and landscape. However, human dimensions are considered as the primary force of landscape change and subsequent forest canopy loss in tropical regions of the world. Many studies have been indicated that roads have a far greater impact on forests than simply allowing access for human use. Similarly, rivers have been used as means of transportation, hence illegal logging and felling further deplete forest canopy density. The main objective of this study was to investigate the spatio-temporal dynamic alterations of Forest Canopy Density (FCD) across with site associated factors such as biophysical, physical and human interferences in tropical region of Nepal from 1988 to 2001. Landsat TM and ETM+ of 1988 and 2001 were used to assess the spatial and temporal dynamic alterations of FCD. This analysis revealed that distance to human settlements at P=<0.01, rivers, human interferences (path and fire) and species composition had a statistically significance at P=<0.05 level. However, other factors did not show any significant relation. So, we concluded that understanding of dynamic alterations of FCD with respect to factors was quite complex phenomena. Other surrounding environment could also playa significant role. A comprehensive analysis could be required to understand such complexities. Therefore, additional factors such as climatic, biophysical, social, and institutional with respect to spatio-temporal variability should be considered for the better understanding of canopy dynamic.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.169-185
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• 2022

The urbanization and increasing rate of population demands effective means of transportation system (basement and tunnels) as well as high-rise building (resting on piled foundation) for accommodation. Therefore, it unavoidable to construct basements (i.e., excavation) nearby piled foundation. Since the basement excavation inevitably induces soil movement and stress changes in the ground, it may cause differential settlements to nearby piled raft foundation. To understand settlement and load transfer mechanism in the piled raft due to excavation-induced stress release, numerical parametric studies are carried out in this study. The effects of excavation depths (i.e., formation level) relative to piled raft were investigated by simulating the excavation near the pile shaft (i.e., H_e/L_p=0.67), next to (H_e/L_p=1.00) and below the pile toe (H_e/L_p=1.33). In addition, effects of sand density and raft fixity condition were investigated. The computed results have revealed that the induced settlement, tilting, pile lateral movement and load transfer mechanism in the piled raft depends upon the embedded depth of the diaphragm wall. Additional settlement of the piled raft due to excavation can be account for apparent loss of load carrying capacity of the piled raft (ALPC). The highest apparent loss of piled raft capacity ALPC (on the account of induced piled raft settlement) of 50% was calculated in in case of H_e/L_p = 1.33. Furthermore, the induced settlement decreased with increasing the relative density from 30% to 90%. On the contrary, the tilting of the raft increases in denser ground. The larger bending moment and lateral force was induced at the piled heads in fixed and pinned raft condition.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.103-114
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• 2007

Sands distributed in Jeju island's coastal areas, Korea, can be classified as silicate sand derived from volcanic rock, carbonate sand derived from shells, and mixed sands containing both silicate and carbonate sands. These three types of sands typically exist in Jeju coastal areas. Samples of silicate, carbonate and mixed sands were obtained from Samyang beach, Gimnyeong beach, and Jeju harbor area, respectively. Compression tests were conducted to assess the compression characteristics of these sands. As a result of these tests, each sand showed different behaviors. For Samyang beach sand, it appeared that initial compression is a larger than the other two sands. For Cimnyeong and Jeju harbor sands, however, the additional compression occurred after initial compression. This could result from the crushing, shattering, and rearrangement of sand particles. In addition, settlement behavior of Jeju harbor ground according to the construction stages was analyzed using the measured data. It showed that in addition to the initial elastic compression, a considerable additional compression occurred with time. The settlements of Jeju harbor ground were predicted by using the elastic settlement calculation methods (empirical methods) and the compression test method. The empirical methods, which did not consider the crushing, shattering, and rearrangement of particles could show smaller result than that occurring actually.

• Journal of the Korean GEO-environmental Society
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• v.13 no.7
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• pp.13-17
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• 2012

Recently, our ocean development paradigm is changing so that the development focus has been moved from the port facility developments to creating useful marine space. This paradigm accords well with the current green technology and helps the growth of service industries and the development from this paradigm can become a national land mark. Accordingly, the concept of creating marine waste landfill by the development of resource recycling technology has been introduced for eco-friendly space as an artificial island in future. Therefore, this study introduces the reactive vertical drainage method that is to pursue the purification of pollutants as well as stabilization of newly deposited soils in marine environments. To install the reactive vertical drainage piles for more effective feasibility and constructability, placements of drainage mid-layer are considered in the geotechnical viewpoint. Consolidation characteristics were evaluated by standard consolidation tests after several types of model test. As s result, the application of mid-layer drainage is strongly recommended in the reactive vertical drainage to quickly stabilize newly deposited soils. And vacuum consolidation method has better consolidation characteristic than vertical loading method in terms of the settlements predicted by additional stress for further use as an artificial island.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.6
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• pp.36-46
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• 2016

Separate transportation card readers that record the amount of transfer volume occurring during movement in-between lines within the metropolitan railway transfer stations do not exist. This research proposes a model to estimate passenger transit movements in transfer stations that adequately reproduces characteristics arising during a transfer trip. The model used in this study assumes that passengers adopt transfer behaviors that minimize their generalized costs during transfer trips. Further, two measures are sought in order to reflect attributes of the metropolitan railway. The first is that similar paths connect origin and destination stations. For this, the M-Similar Paths method is applied to the model to identify the similar paths that arise. The second is that passengers perceive increasing number of transfers as additional transfer costs, which is reflected by means of the Stepwise Transfer Coefficient. Two case studies of metropolitan railway are used to propose measures for analysis of transfer trips. Twenty directional transit phenomena are reproduced for Sindorim railway station. Aggregate directional transit(A), aggregate inter-line transit(B), and B/A are calculated on a percentage basis for 33 metropolitan railway transfer stations, and using this, the functional role of transfers is explored.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.380-387
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• 2016

Considering that the Seoul subway sector is expected to see extension of lines, addition of stations, and changes of operating companies, a review is needed to identify ways to eliminate or minimize financial deficits in its operation. As for deficits from the operation, additional businesses for extra income have been suggested as alternatives, but inasmuch as Western urban development (that of the subway containment area) may not be applicable to Korean settings, a practical alternative is to maximize income by efficient use of rental facilities that are located inside station properties. This alternative requires the estimation of appropriate facility size and rent for each station; few, however, have addressed this topic. At this juncture, this study aimed to draw an equation for estimating the sizes and rents of station properties by reflecting characteristics of lines and locations; a case study was performed for Subway Lines 5 and 6. Analytical findings are that rental facility sizes and rental incomes are affected mainly by the subway ridership and transport revenues, whereas the influence of ground-level commercial activity is relatively weak. A particularly great influence was found to be the value of apartment housing in areas through which the subway lines run. Stations on Line 5, which runs through areas of high-value housing, were assigned smaller facility sizes and higher rents than those on Line 6, which covers areas with relatively low housing value. The equation suggested in this study would make possible more practical feasibility studies when the need arises to estimate sales of new or extended facilities affiliated with stations.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.4
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• pp.428-438
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• 2016

The aim of this study, in order to reduce the support burden of dementia primary caregiver, within the framework of long-term care insurance system to present its founding model for the development of new services. Previous research as analytical materials and based on the CARE study between 2012 to 2013. Primary caregiver burden of patient are both physical, psychological and economic aspects as well as difficulties in many aspects and had influence on many factors such as age, care burden, economic, health, and social support. It also came high-risk primary caregiver suffer from depression. This primary caregiver to take advantage of the elderly long-term care insurance system implemented at the time of the institutional support necessary for since 2008, presented additional services in this study. Of increasing the small sizes day care center (tentative name) to open an as established in the settlements at a scale of less than nine, within 5 minutes from the residence, limited dementia by expertise in the disease home care services scale model of the current system service It was to improve the quality of existing shares, small group sizes for day care centers and community life apart.