• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.141-155
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• 2023

Monitoring technology based on electrical resistivity is widely used for non-destructive data collection and health analysis of underground structures and tunnels. Vulnerable sections such as fault zone generates many problems during construction of the tunnel. These problems cause displacement and stress changes of the ground. Therefore, it is necessary to predict the state of the fault zone section to ensure the mechanical stability of the underground structure. Monitoring the size of joints and the porosity of the fillings is essential for rocks. Previous studies have not considered the variety of fillings in rock joints. In this study, electrical resistivity tests were conducted according to the particle mixing state of the sandy fillings. When the size of fillings is decreased at the constant porosity, the electrical resistivity tends to increase. The results of this study are expected to be useful as basic electrical resistivity data for predicting the ground conditions and evaluation of the ground behavior that is containing sandy fillings in the rock joint for tunnels.

• Journal of the Society of Disaster Information
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• v.19 no.2
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• pp.305-312
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• 2023

Purpose: Although the damage caused by abnormal temperatures is extensive, blow-up or black ice is typical in concrete structures. In this study, PCM with high phase change energy was mixed with concrete to reduce temperature damage to concrete pavement. Method: In order to reduce temperature damage to low temperatures and high temperatures, capsule-type PCM with phase change temperatures of 4.5℃ and 44℃ was replaced by 10%, 30%, and 50%, and thermal performance experiments and compressive strength experiments were conducted using thermocouples and variable chambers. Result: As a result of the thermal performance experiment, it was found that the incorporation of PCM improves temperature resistance by up to 25% or more, and increases thermal resistance at all temperatures with high specific heat when substituted in large amounts. As a result of the compression strength experiment, a substitution of 30% or more resulted in a decrease in the compression strength, and a large strength difference was shown based on the phase change temperature of the PCM. Conclusion: The incorporation of PCMs has been shown to increase the thermal performance of concrete, with the greatest increase in thermal performance near the phase change temperature of PCM. In addition, a small strength reduction of 10% to 20% occurs at the highest substitution rate of 50% substitution, so there is no significant problem with usability, and additional PCM substitution is expected to improve thermal performance.

• Journal of the Society of Disaster Information
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• v.19 no.2
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• pp.313-325
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• 2023

Purpose: According to the recent occurrence statistics of ground accidents, ground subsidence and subsidence have become social problems as the frequency has increased centering around the downtown areas. This study tried to clarify risk of detailed factors which have an effect on subsidence. Method: For the study, detailed risk factors of 28 foundations were mainly drawn through the materials, precedent studies, and research reports shown by analyzing JIS' accident cases from 2016 to September 6, 2022 and by taking advice from an excavation expert. And risk was assessed by conducting a survey on 12 subsidence experts from the universities, research institutes, and industries and applying Fuzzy-FMEA to it. Result: It has found that damage of sewer pipes is 24.99% of overall risk, followed by excavation work (17.34%), water pipes (14.84%), and poor compaction (refill) (13.93%). And it has found that risk of damaging utilities (water pipes, sewer pipes, and other utilities) is highest, followed by poor construction works (excavation work, damage of sewer and water pipes, and other utility work) and poor compaction (refill). Conclusion: This shows that risk of subsidence factors judged by experts is similar with JIS' cases of ground subsidence.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.58-70
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• 2023

Based on the current state of safety management for small-scaled old buildings, this study identified problems and proposed improvement plans. The study investigated the current status of safety management based on relevant laws and government and financial portal data, as well as budget documents related to the targets of safety management, the organization responsible for safety management, and the budget required for organizational operation. As a result, the study revealed the problem of safety management blind spots for buildings that are not included in the legal safety inspection targets. It also identified difficulties in securing specialized personnel for the operation of local building safety centers and financial constraints for the operation of building safety special accounting. To address these issues, the study proposed measures such as expanding the scope of safety inspection targets for small-scaled old buildings to reduce safety management blind spots, improving compensation regulations for specialized personnel, setting a minimum ratio for enforcement fines to secure financial resources, and gradually adjusting building permit fees. The study aimed to contribute to improving the efficiency of safety management for small-scaled old buildings based on these proposed measures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.395-401
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• 2009

One of the key design factors for the ventilation and safety system at extra long tunnel is the airflow velocity induced by the natural ventilation force. Despite of the importance, it has not been widely studied due to the complicated influencing variables and the relationship among them is difficult to quantify. At this moment none of the countries in the world defines its specific value on verified ground. It is also the case in Korea. The recent worldwide disasters by tunnel fires and demands for better air quality inside tunnel by users require the optimization of the tunnel ventilation system. This indicates why the natural ventilation force is necessary to be thoroughly studied. This paper aims at predicting the natural ventilation force at a 11 km-long tunnel which is in the stage of detailed design and will be the longest vehicle tunnel in Korea. The concept of barometric barrier which can provide the maximum possible natural ventilation force generated by the topographic effect on the external wind is applied to estimate the effect of wind pressure and the chimney effect caused by the in and outside temperature difference is also analyzed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.6
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• pp.407-416
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• 2010

A new tunnel auxiliary method is proposed in this paper which utilizes the concept of cavity expansion for tuunel reinforcement by forming an umbrella arch on the roof of tunnel. When an inflatable pipe is inserted and expanded by pressure in the bore hole of umbrella arch, the ground around the bore hole can be compacted so that the stress condition above the tunnel perimeter is favorably changed. In order to verify the reinforcement effect of new concept, pilot-scale chamber test, trapdoor test and numerical analysis were performed and compared. In pilot-scale chamber test, three types of inflatable pipes are tested to verify the capability of expansion, and the results arc compared with analytical results obtained by applying cavity expansion theory and with results obtained from finite clement analysis, and the experimental results showed agreeable matches with analytical and numerical ones. Numerical analysis of a tunnel and trapdoor test applied with the inflatable pipes are also performed to figure out the reinforcement effect of the proposed techniques, and the results implied that the new method with 3 directional inflatable pipe (no pressure to downward direction) can contribute to reduce tunnel convergence and face settlement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.77-84
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• 2023

As the installation of solar panel accelerates, so does the number of solar panels reaching their end-of-life (EOL). However, the EOL solar panels is becoming a concern, as they contain potentially hazardous materials and are not easily recycled. Coping strategies such as effective collection, disposal, and recycling methods will be important to manage the growing number of EOL solar panels in the coming years.Therefore, many studies have focused on the development of EOL solar panel recycling technology. One recycling technology for EOL solar panels applicable to the construction field is the application of extracted tempered glass from EOL solar panels as construction materials. This study summarized the EOL solar panel disassembly technology and evaluated the mechanical properties of mortar using extracted tempered glass as fine aggregate. The results showed that when tempered glass was used as a fine aggregate in mortar, the compressive strength, flexural strength, and macro pores in the 1-3 ㎛ with 200-300 ㎛ range were affected, regardless of the disassembly technology of EOL solar panels. Especially, we found that the mechanical performance of mortar using chemically treated tempered glass was noticeably decreased due to changes in the chemical composition of the extracted tempered glass resulting from the removal of K₂O and CuO due to chemical reactions. Meanwhile, it was found that when fly ash was used as a binder, the reduction of mechanical performance could be alleviated.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.71-83
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• 2009

Shotcrete is an important primary support for tunnelling in rock. The quality control of shotcrete is a core issue in the safe construction and maintenance of tunnels. Although shotcrete may be applied well initially onto excavated rock surfaces, it is affected by blasting, rock deformation and shrinkage and can debond from the excavated surface, causing problems such as corrosion, buckling, fracturing and the creation of internal voids. This study suggests an effective non-destructive evaluation method of the tunnel shotcrete bonding state applied onto hard rocks using the impact-echo (IE) method and ground penetration radar (GPR). To verify previous numerical simulation results, experimental study carried out. Generally, the bonding state of shotcrete can be classified into void, debonded, and fully bonded. In the laboratory, three different bonding conditions were modeled. The signals obtained from the experimental IE tests were analyzed at the time domain, frequency domain, and time-frequency domain (i.e., the Short- Time Fourier transform). For all cases in the analyses, the experimental test results were in good agreement with the previous numerical simulation results, verifying this approach. Both the numerical and experimental results suggest that the bonding state of shotcrete can be evaluated through changes in the resonance frequency and geometric damping ratio in a frequency domain analysis, and through changes in the contour shape and correlation coefficient in a time-frequency analysis: as the bonding state worsens in hard rock condition, the autospectral density increases, the geometric damping ratio decreases, and the contour shape in the time-frequency domain has a long tail parallel to the time axis. The correlation coefficient can be effectively applied for a quantitative evaluation of bonding state of tunnel shotcrete. Finally, the bonding state of shotcrete can be successfully evaluated based on the process suggested in this study.

• 한국노년학
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• v.32 no.2
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• pp.649-668
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• 2012

The purpose of this study ahead of the aging society in Korea to prevent problems of the elderly aged new addiction Internet Addiction and identify factors affecting the quantitative increase and qualitative improvement beyond that aims to promote. To this end, residents in Seoul over the age of 60's targets, local welfare, cultural centers, senior centers and other research in the area through one-on-one interviews were conducted the survey. Findings The average degree of Internet addiction elderly 36.16 points (SD = 10.02) and the distribution of at least 20 points to 65 points, respectively. Factors affecting the degree of Internet addiction as a computer time (β = .248, p <.001), mon allowance (β = .180, p <.01), age (β = .139, p <.01) and social support (β = .087, p <.05), self-efficacy (β = - .078, p <.05), most used location (β = - .116, p <.05), degree of family relationship (β = - .147, p <.01), housing type (β = - .153, p <.01), were of the order, this factor was 17.6% of the variance. In other words, the more computer time, the higher the age, the more mon allowance, housing is not self, the lower the degree of family relationship, the house is not a place most used, lower self-efficacy, social support is high As increasing the degree of Internet addiction was thought to be the two predictor variables. Survey results to target the elderly through the Internet addiction group psychotherapy program implementation, and production and distribution of manuals related to Internet use and addiction-related factors, according to the case-by-case Case management services are tailored to be done, and the Internet in general for seniors potential risks related to use in training and preventive services for the elderly will need to be made.

• 한국노년학
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• v.29 no.4
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• pp.1577-1589
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• 2009

The purpose of this study was to compare the health status, functional status, and home environment hazards by the fear of falling and explore the factors that contribute to the fear of falling. This was a descriptive study. Data were collected for two years with 973 older adults who enrolled in a health center at A city. Trained nurses visited subjects' home and collected data using Resident Assessment Instrument MDS-HC. The average age of the subjects was 76.8 (±7.6) and female was 74.8%. 20.7% of subjects reported fear of falling. In terms of the fear of falling, two groups were compared. There were significant differences in vision, urinary incontinence, pain that interrupts daily activity, unstable gait, comorbidities, frequency of depressive or anxious sign. The greater the age, IADL and ADL dependency, comorbidities, unstabled gait, the more fear of falling. In conclusion, this study reassured the importance of assessing the major factors related to fear of falling such as age, IADL and ADL, comorbities, gait among older adults. This study will contribute to establish strategies for preventing fall. Reducing the fear of falling through the comprehensive nursing intervention will ultimately improve the quality of life in the elderly.