• Tunnel and Underground Space
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• v.6 no.1
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• pp.19-29
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• 1996

Back analysis model, capable of calculating the mechanical properties and the in-situ stresses of jointed rock mass, was developed based on the inverse method using a continuum theory. Constitutive equation for the behavior of jointed rock contains two unknown parameters, elastic modulus of intact rock and stiffness of joint, hence algorithm which determines both parameters simultaneously cannot be established. To avoid algebraic difficulties elastic modulus of intact rock was assumed to be known, since the representative value of which would be quite easily determined. Then, the ratio ($\beta$) of joint stiffness to elastic modulus of intact rock was assigned and back analysis for the behavior of jointed rock was carried-out. The value $\beta$ was repeatedly modified until the elastic modulus from back analysis became very comparable to the predetermined value. The joint stiffness could be calculated by multipling the ratio $\beta$ to the final result of elastic modulus. Accuracy and reliability of back analysis procedure was successfully testified using a sample model simulating the underground opening in the jointed rock mass. Applicability of back analysis model for the underground excavation in practice was also verified by analyzing the mechanical properties of jointed rock in which underground oil storage cavern were under construction.

• Tunnel and Underground Space
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• v.25 no.1
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• pp.107-114
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• 2015

This study focuses on assessing risks which might occur in operation stage of CAES storage cavern and analyzing fire scenarios for the risk that have been assessed with highest risk level. Risks in operation stage were categorized into upper risk group and lower risk group. Components of upper risk group are technical risk, facility risk and natural disaster risk. Lower risk group is composed of 11 sub-risks. 20 experts were chosen to survey questionnaires. ANP model was applied to analyze the relative importance of 11 sub-risks. Results of risk analysis were compared with risk criterion to set risk priorities, and the highest risk was determined to be 'occurrence of the fire within the management opening'. Three fire scenarios were developed for the highest risk level and FDS (Fire dynamics Simulator) was used to analyze these scenarios. No. 3 scenario which air blows from tunnel into outside atmosphere represented that a rate of smoke spread was the fastest among three fire scenarios and a smoke descended most quickly below the limit line of breathing. Thus, No. 3 scenario turned out to be the most unfavorable condition when operating staffs were evacuated from access tunnel.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.455-465
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• 2016

The collapse of underground mine development void for mineral resources can cause the subsidence of ground surface. In order to prevent the subsidence of ground, data such as maps or pictures of past mining site is important information for current mine reclamation works. In particular, mine subsidence management was based on mining maps and pictures. The process of the mining area surveys, safety evaluation, and ground reinforcement are normally possible with information such as maps and pictures in past mining. During the Japanese colonial period and 1960's, a lot of mines were developed in Korea indiscriminately. However, mining information at that time is limited to use. In the future, mining information will become even more rare. MIRECO intends to establish a realistic alternative solution. In this study, the basic numerical information of developed mine tunnels in Korea is statistically reviewed, and advanced underground cavity measuring technology was studied. 4,473 mine tunnel opening data of 1,784 abandoned mines in korea were collected and sorted. As a result of the analysis, the average value of small mine tunnel openings in Korea was 1.982 m in height and 1.959 m in width. The mean value of shape factor was analyzed as 0.485. The summary of these numerical mine data will be helpful for understanding and researching Korean abandoned mines. Therefore, the development of measurement technology for abandoned mine cavities and tunnels is expected to facilitate more effective mine subsidence management works in Korea.

• Journal of Chest Surgery
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• v.42 no.1
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• pp.96-99
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• 2009

We report here on a case of a ruptured sinus of a valsalva aneurysm into the left ventricle with the rupture site communicating with both the left coronary sinus and the noncoronary sinus in a 37-year-old male who presented with symptoms of congestive heart failure. Echocardiography showed a sac-like structure around the sinus of valsalva, an enlarged left ventricle (LV) and severe aortic regurgitation, which all suggested a ruptured sinus of a valsalva aneurysm or an aortic-left ventricular tunnel. The operative findings revealed that both the left coronary sinus and the noncoronary sinus had an opening into the left ventricle. The proximal opening into the LV was closed with bovine pericardium and the aortic root was replaced with a composite graft (a 21 mm St. Jude Epic Supra tissue valve and a 24 mm Hemashild graft) by the modified Bentall procedure. The patient was discharged on the 15th postoperative day, and he was regularly followed up for 2 months. We report on this case due to its rarity and to describe the surgical repair techniques.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.32 no.4
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• pp.120-131
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• 2014

Sajikdan(a sort of national shrine in Korea) built at the time of foundation of Joseon was entrenched into Sajik Park going through Japanese colonial era and recently the efforts to restore it is in progress. The details of change in Sajikdan in terms of diachronic analysis are as follows: Firstly, the first period refers to one prior to Japanese colonial era from the first king (also named as "Taejo" in Korean) of the Joseon Dynasty, during which it secured and strengthened the presence as a place for performing important national rites in a nation. It was built on the foot of Inwangsan Mt. at the time of the first king in Joseon Dynasty at first, was destroyed fully by fire during a Japanese Invasion period to Korea(1592-98) and afterward its ancestral ritual facilities were completed under the regime of Youngjo. However, as Japanese intervention coming to the fore, its place was destroyed and then ancestral rites were also abolished in 1908. Secondly, next period falls on 1910 to 1944 when it was transformed and entrenched into a park by the Japanese Empire. While facilities related to a park and an heterogeneous building around the part of boundary were set up, the area of altar, a ritual house and d door of Sajikdan were also designated as historical remains and treasures. Thirdly, this period refers to one from Korea's liberation year from Japanese colony(1945) to the year of 1984 when it had a mixed placeness with the statues, monuments and buildings with heterogeneous nature built. Furthermore, a door of Sajikdan was removed and reconstructed over twice due to opening of Sajik Tunnel. Fourthly, a final period falls on 1985 to the present when efforts are in progress to restore the historicity and symbolism of Sajikdan. A plan for restoration is promoted but now is a difficult time suffering from troubles caused by residents' resistance. Scrutinized historical researches through excavation investigation and residents' understanding are required altogether for restoration of Sajikdan.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.38-58
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• 2018

The ventilation system plays a crucial role in underground mine safety. The main objective of the ventilation system is to supply sufficient air to dilute the contaminated air at working places and consequently provide tenable environment during the normal operation, while it also should be capable of controlling the fire propagation and facilitate rescue conditions in case of fire in mines. In this study, a smoke control fan was developed for the auxiliary ventilation as well as the fire smoke exhaust. It works as a free-standing auxiliary fan without tubing to dilute or exhaust the contaminated air from the working places. At the same time, it can be employed to extract the fire smoke. This paper aims to examine the smoke control efficiency of the fan when combined with the current ventilation system in mines. A series of the site experiments and numerical simulations were made to evaluate the fan performance in blind entry development sites. The tracer gas method with SF6 was applied to investigate the contaminant behavior at the study sites. The results of the site study at a large-opening limestone mine were compared with the CFD analysis results with respect to the airflow pattern and the gas concentration. This study shows that in blind development entry, the most polluted and risky place, the smoke fan can exhaust toxic gases or fire smoke effectively if it is properly combined with an additional common auxiliary fan. The venturi effect for smoke exhaust from the blind entry was also observed by the numerical analysis. The overall smoke control efficiency was found to be dependent on the fan location and operating method.

• Tunnel and Underground Space
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• v.28 no.3
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• pp.258-276
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• 2018

The accurate and quantitative ground information on the hydraulic conductivity characteristics of rock mass is one of the key factors for evaluation of the hydro-geological behaviour of rock mass around an excavated opening under high water pressure. For tunnel and rock structures in seabed, where the sea acts as an infinite source of water, its importance become greater with increasing construction depth below sea level. In this study, to improve the problems related with poor system configuration and incorrect data acquisition of previous hydraulic packer testing equipment, we newly developed an integrated main frame and 30 bar level waterproof downhole sonde apparatus, which were optimized for deep hydraulic packer test in seabed rock mass. Integration of individual test equipment into one frame allows safe and efficient field testing work on a narrow offshore drilling platform. For the integrated type main frame, it is possible to make precise stepwise control of downhole net injection pressure at intervals of $2.0kg_f/cm^2$ or less with dual hydraulic oil volume controller. To ensure the system performance and the operational stability of the prototype mainframe and downhole sonde apparatus, the field feasibility tests were completed in two research boreholes, and using the developed apparatus, the REV(Representative Elementary Volume) scale deep hydraulic packer tests were successfully carried out at a borehole located in the basalt region, Jeju. In this paper, the characteristics of the new testing apparatus are briefly introduced and also some results from the laboratory and in-situ performance tests are shown.

• Tunnel and Underground Space
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• v.13 no.5
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• pp.397-402
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• 2003

Generally it is likely that rock mass properties are expressed not by a mean value but by values with variation due to its characteristic uncertainty. This characteristic is one of the most important parts for the design of undergound structures, but yet to be fully examined. Stochastic finite element method (SFEM) is contrary to deterministic finite element method in its concept as the former has been developed in order to take the randomness of structural systems into account. Using SFEM, the response variability of structural system can be obtained and it leads probabilistic stability of structure to be analyzed. In this study, displacement response variability of circular opening with hydrostatic stress field are analyzed in terms of rock mass properties having a certain mean and a standard deviation using the SFEM. The analyzed response variability shows that the necessity of probabilistic stability analysis of underground structures using reliable mean value and standard deviation of deformation modulus.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3594-3599
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• 2009

The train control system used in Gyeongbu-line is classified in ATC, IXL and CTC. The ATC data related to speed and space control for trains are transmitted from wayside to onboard by way of UM71 AF track circuits and BSP Loop. The information transferred by track circuits is composed of operation data which directly influence to the train operation and the information transferred by BSP Loop is used in the section which requires the additional data transmission about the particular track-side environment such as tunnel, hot box detector or insulated section. In this paper, for the BA type turning unit of the UM71 AF track circuits which is mainly used in the linking section of existing and high-speed lines from the opening of the Gyeongbu line till the present, we not only analyze the characteristics of BA but also compare and analyze baseline values and the measured values. With this analysis, we will be able to propose how to solve the problems about operation and maintenance such as track circuit malfunctions of the relevant sections.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.263-273
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• 2007

When a tunnel or an underground structure is excavated in deep geological environments, the failure process is affected and eventually dominated by stress-induced fractures growing preferentially parallel to the excavation boundary. This fracturing is generally referred to as brittle failure by spatting and slabbing. Continuum models with traditional failure criteria such as Hoek-Brown or Mohr-Coulomb criteria have not been successful in prediction of the extent and depth of brittle failure. Instead cohesion weakening and frictional strengthening (CWFS) model is known to predict brittle failure well. In this study, CWFS model was applied to predict the brittle failure around a circular opening observed in physical model experiments. To obtain the input parameters for CWFS model, damage-controlled tests were carried out. The predicted depth and extent of brittle failure using CWFS model were compared to the results of the physical model experiment and numerical simulation using traditional model.