• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.1
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• pp.91-104
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• 2014

An Excavation Damaged Zone (EDZ), in which rock properties are permanently changed due to blasting impact or stress redistribution, can influence the behavior and stability of structures. In this study, the mechanical stability of an underground opening was simulated by using FLAC, which is a two-dimensional modeling code, with a consideration of EDZ. A sensitivity analysis was also carried out with fractional factorial design. From the modeling, it was found that the behavior and the stability of an underground tunnel are strongly dependent on the existence of the EDZ. The sensitivity analysis showed that the key parameters affecting the factor of safety around the tunnel are in-situ stress ratio, depth, cohesion, reduction ratio, internal friction angle, and height and width of the tunnel. It is necessary to consider the EDZ, which can significantly affect mechanical stability in tunnel design.

• Explosives and Blasting
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• v.33 no.4
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• pp.7-13
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• 2015

Recently, as the demand for development and utilization of underground space is increasing worldwide, the blast damaged zone has become a major issue in constructing underground structures. In this study, to verify the explosion modelling method for blast-damaged zone (BDZ) around underground cavern, a series of small-scale test blasts was conducted using the concept of momentum trap. According to the test results, the input parameters to the numerical model (ANSYS LS-DYNA) were corrected. It is concluded that the suggested method of miniature blasting and numerical modelling using the MT concept well simulates the velocity of the MT projectile under given conditions.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.1
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• pp.75-94
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• 2019

As the present single-layer repository concept requires too large an area for the site of the repository, a multi-layer repository concept has been suggested to improve the disposal density. The effects of the excavation damaged zone around the multi-layer repository constructed in the deep host rock on the temperature distribution in the repository were analyzed. For the thermal analysis of the multi-layer repository, the hydrothermal model was used to consider the resaturation process occurring in the buffer, backfill and rock. The existence of an excavation damaged zone has a significant effect on the temperature distribution in the repository, and the maximum peak temperatures of double-layer and triple-layer repositories can rise to $7^{\circ}C$ and $12^{\circ}C$, respectively depending on the size of the excavation damaged zone and the degree of decrease of the thermal conductivity. The dominant factor affecting the peak temperature in the multi-layer repository is the decrease of thermal conductivity in the excavation damaged zone, and the excavation damaged zone formed around the deposition hole has more significant effects on the peak temperature than does the excavation damaged zone formed around the disposal tunnel.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.485-498
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• 2015

Structural analysis for a large-scale fault in Maegok-dong, Ulsan, was carried out based on filed-works to investigate the geometric and kinematic characteristics of the fault as well as its Quaternary slip. As results, a series of repeated stratigraphy, minor faults, fracture zones, and deformation band clusters are observed over a distance of about 100 m in the first studied site consisting of sedimentary rocks, which may indicate the damage zone of a large-scale fault in this site. In the second site, mainly composed of granitic clastic rocks, a large-scale thrust fault is expected based on low-angle dipping faults showing branched and/or merged patterns. Age of the last slip on this fault was restrained as after 33,275 ± 355 yr BP based on radiocarbon dating for organic material included in the gouge zone. Dimension of fault damage zone, dominant sense of slip, and age of the slip event associated with the fault suggest that these structures have a close relationship with the Ulsan Fault and/or Yeonil Tectonic Line, which are well-known large-scale neotectonic structural features around the study area. Therefore, it is necessary to study the characteristics of the faults in detail based on structural geology and paleoseismology in order to ensure seismic and geologic stability of the buildings under construction, and to prevent geologic hazards in this area.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2008.05a
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• pp.167-168
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• 2008

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2007.11a
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• pp.204-205
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• 2007

• Proceedings of the KSEE Conference
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• 2008.04a
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• pp.21-31
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• 2008

• Journal of Chest Surgery
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• v.37 no.9
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• pp.774-780
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• 2004

Although traumatic thoracic aortic rupture is potentially a fatal condition requiring surgical attention, the presence of concomitant injury involving other parts of the body may greatly increase the risk of cardio-pulmonary bypass. We report our experience of treating associated injuries prior to the thoracic aortic rupture in these patients. Material and Method: From 1997 to 2003, the medical records of 24 traumatic aortic rupture patients were retrospectively reviewed and checked for the presence of associated injury, surgical method, postoperative course, and complications. Surgical technique comprised thoracotomy with proximal anastomosis under deep hypothermic circulatory arrest followed by side arm perfusion to reestablish cerebral circulation. CSF drainage was performed to prevent lower extremity paraplegia. Result： Major concomitant injuries (n=83) were noted in all of the reviewed patients, Of these, there were 49 thoracic injuries, 18 musculoskeletal injuries, and 13 abdominal injuries, Operations for associated injuries (n=16) were performed in 12 patients on mean 7.6$\pm$12.6 days following the injury. The diagnosis of aortic rupture at the time of injury was detected in only 18 patients. Delayed surgery of the thoracic aorta was performed on average 695$\pm$1350 days after injury and there were no deaths or progression of rupture in any of these patients during the observation period. There were no operative deaths and no major postoperative complications. Conclusion: Treating concomitant major injuries prior to the aortic injury in traumatic aortic rupture may reduce surgical mortality and morbidity.

• Journal of Korean Orthopaedic Sports Medicine
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• v.6 no.2
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• pp.99-104
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• 2007

Purpose: To research match injuries related to Taekwondo in adolescent athletes and find out preventing injuries. Materials and Methods: We analyzed 162 match injuries of middle and high school athletes, who were surveyed in 2005 and 2006 national tournament. Results: Among 162 match injuries, injuries in foot and hand were the most common and there were 35 cases in serious injuries such as fracture, open dislocation, open fracture of epiphyseal plate and so on. The very fast speed and destructive power of Takwondo athlete can cause open dislocation of great toe and can cause fracture of foot and upper extremity when kicking. Conclusion: We consider that injured athletes need proper treatments and sufficient rest not to accumulate training injuries and match injuries and need to improve mats of stadium, braces for feet and hands and put on braces for elbows to prevent match injuries.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.257-270
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• 2000

The objective of this study is to develop a damage model based on damage mechanics that can be used to analyze the mechanical behavior of structures with defects and the global behavior of damaged structures. A modified second order damage tensor that can be applied to finite element analysis is used to reflect the effect of damage. The damage stress computed from the effective stress is considered as an additional loading term acting on nodes and can represent the effect of crack surface. The accuracy of the proposed algorithm is verified by comparing the analysis results with the experimental data from other studies and the analysis results based on transverse isotropic theory. The developed damage model is applied to the analyses of structures with cracks under linear elastic condition. The comparisons confirmed that the quantitative analysis of the structural behavior due to crack orientation and multiple sets of cracks is possible. Also, the damage caused by rock excavation and fault zone is analyzed. The results also showed that the developed model can effectively analyze the global behavior of damaged structures.