• Tunnel and Underground Space
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• v.25 no.2
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• pp.125-132
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• 2015

As for noise and vibration occurring due to construction near fish farms, engineering and the technical opinions of experts in different areas were excluded in calculating any damage. The victims tend to present only biological consulting-based opinions while construction companies tend to present information on general construction noise and vibration as they have little biological knowledge on fish. So, the National Environmental Dispute Medication Commission presented specific damage standard in 2009 through studies on standard in calculating compensation and damage assessment of farm-raised fish that were affected by noise and vibration. Currently, 140 dB re $1{\mu}Pa$ is accepted as damage standard of underwater noise in the country. This standard is the RMS value of continuous sounds for more than a second, not the impulsive sounds. To look up the data on existing studies, fish showed different reactions to underwater sounds according to the different kinds of fish such as ostariophysan or non-ostariophysan, and pinnipeds or non-pinnipeds. So, this study will present damage standards for impulsive sounds in consideration of the differences in the characteristics of the impulsive and continuous sounds.

• Tunnel and Underground Space
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• v.26 no.1
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• pp.1-11
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• 2016

This study deals with the case that was the field application of the microseismic monitoring techniques for the stability monitoring in a domestic mine. The usefulness and limitations of the microseismic techniques were examined through analyzing the microseismic monitored data. The target limestone mine adopted a hybrid room-and-pillar mining method to improve the extraction ratio. The accelerometers were installed in each vertical pillar within the test bed which has the horizontal cross-section $50m{\times}50m$. The measured signals were divided into 4 types; blasting induced signal, drilling induced signal, damage induced signal, and electric noise. The stability analysis was performed based on the measured damage induced signals. After the blasting in the mining section close to the test bed, the damage of the pillar was increased and rockfall near the test bed could be estimated from monitored microseismic data. It was possible to assess the pillar stability from the changes of daily monitored data and the proposed safety criteria from the accumulated monitored data. However, there was a difficulty to determine the 3D microseismic source positions due to the 2D local sensor arrays. Also, it was needed to use real-time monitoring methods in domestic mines. By complementing the problems encountered in the mine application and comparing microseismic monitored data with mining operations, the microseismic monitoring technique can be used as a better safety method.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.173-182
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• 2012

Entry and exits of the rest area are sections where designed speed can be rapidly change and also a weak traffic safety section. In addition, two tasks can be performed simultaneously at entry of the rest area, particularly searching for deceleration and parking spaces/parking sides etc. Thus, design criteria is required in order to procure the stability of accessed vehicle. In case of Korea, geometric structure design criteria of entry facilities, such as toll-gate, interchange, junction etc was established. However there are no presence in a detailed standards for geometric structure of the rest area which affiliated road facilities. In this study, Derive problems in regards to the entry of geometric structure of resting areas by utilizing a sight survey and an investigation research of traffic accidents. The survey was targeting 135 general service areas. After Classifying the design section of resting areas' entry as well as derive design elements on each section, a speed measurement by targeting entry of rest areas and car behavior surveys were performed, then each element's minimum standard was derived through the analyses. According to the speeds at the starting/end point of entrance connector road, the minimum length of the entrance connector road is decided as 40m using Slowing-down length formula and based on the driving pattern, the range of the junction setting angle of the entrance connector road is defined as $12^{\circ}{\sim}17^{\circ}$. Suggest improvement plans for existing rest areas that can be applied realistically. This should be corresponded to the standards of entry and exit of developed rest areas.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.403-411
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• 2012

In recent, the using of the hydraulic filling method has increased on the underground reinforcement of the abandoned mine in Korea, however it is the lack of research on the efficient filling method. In this study, tank model tests and field tests were conducted for development of tip device for filling efficiency improvements on the hydraulic filling method. In tank model experiments, the filling efficiency was evaluated according to the form and angle of the nozzle on tip device in the same condition. Then tip device model designed by tank model tests was applied to the field experiment. As a result, the amount of filling of nozzle $90^{\circ}$ tube is increased by approximately 18% compared to the common vertical injection pipe. The angle of repose was $30.82^{\circ}$. Filling hole spacing in the field is usually designed from 5m up to 10m assumed to be $40^{\circ}$ of the angle of repose. According to the results of this study, it is possible that the filling hole spacing expands at least 10m up to 15m applied to be $30^{\circ}{\sim}35^{\circ}$ of the angle of repose. Therefore, it is expected to be economical and efficient mine filling.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.429-437
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• 2012

This study predicted temperature in the disposal tunnels using computational fluid dynamics based on natural ventilation quantity that comes from high altitude and temperature differences that are the characteristics of high level waste repository. The result of the previous study that evaluated quantitatively natural ventilation quantity using a hydrostatic method and CFD shows that significant natural ventilation quantity is generated. From the result, this study performed the prediction of temperature in disposal tunnels by natural ventilation quantity by the caloric values of the wastes, at both deep geological repository and surface repository. The result of analysis shows that deep geological repository is effective for thermal control in the disposal tunnels due to heat transfer to rock and the generation of sufficient natural ventilation quantity, while surface repository was detrimental to thermal control, because surface repository was strongly affected by external temperature, and could not generate sufficient natural ventilation quantity. Moreover, this study found that in the case of deep geological repository with a depth of 200 m, the heatof about $10^{\circ}C$ was transferred to the depth of 500 m. Thus, it is considered that if the high level waste repository scheduled to be built in the country is designed placing an emphasis on thermal control, deep geological repository rather than surface repository is more appropriate.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.432-439
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• 2009

For more reliable estimation of seismic source, attenuation properties and dynamic ground property, site amplification function should be considered. Among various estimation methods, this study used the Nakamura's method (1989) for estimating site amplification characteristics. This method was originally applied to the surface waves of background noise and therefore there are some limitations in applying to general wave energy. However, recently this method has been extended and applied to the S wave energy successfully. This study applied the method to S wave and Coda wave energy, which is equivalent to the backscattered S wave energy. We used more than 60 observed ground motions from 5 earthquakes which were occurred recently, with magnitude range from 3.6 to 5.1. Each station showed characteristic site amplification property in low-, high- and resonance frequencies. Some of the stations showed as high as 4 times of site amplification in the range of specific frequencies, which may imply abnormal small scale geologic strata below the station or development of various trapped modes in the basin structure. Moreover, removal of site amplification can give us more reliable seismic source and attenuation parameters, addition to the seismic hazard estimation.

• Tunnel and Underground Space
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• v.24 no.4
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• pp.297-307
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• 2014

Cavern Thermal Energy Storage system stores thermal energy in caverns to recover industrial waste heat or avoid the sporadic characteristics of renewable-energy resources, and its advantages include high injection-and-extraction powers and the flexibility in selecting a storage medium. In the present study, the structural stability of rock mass pillar between these silo-type storage caverns was assessed using a coupled thermal-mechanical model in $FLAC^{3D}$. The results of numerical simulations showed that thermal stresses due to long-term storage depended on pillar width and had significant effect on the pillar stability. A sensitivity analysis of main factors indicated that the influence on the pillar stability increased in the order cavern depth < pillar width < in situ condition. It was suggested that two identical caverns should be separated by at least one diameter of the cavern and small-diameter shaft neighboring the cavern should be separated by more than half of the cavern diameter. Meanwhile, when the line of centers of two caverns was parallel to the direction of maximum horizontal principal stress, the shielding effect of the caverns could minimize an adverse effect caused by a large horizontal stress.

• Tunnel and Underground Space
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• v.23 no.6
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• pp.480-492
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• 2013

After the introduction of geothermal power generation technology based on engineering reservoir creation that can be applied on non-volcanic region, industrial need for studies on the efficient and economic execution of costly deep-depth drilling work becomes manifest increasingly. However, since it is very difficult to predict duration and cost of boring work with acceptable reliability because of many uncertain events during the execution, efficient and organized work management for drilling is not easily achievable. Especially, the round trip that discretely occurs because of the abrasion of bit takes more time as the depth goes deeper and it has a great impact on the work performance. Therefore, a technology that can simulate the occurrence timing and depth of round trip in advance and therefore optimize them is essentially required. This study divided the abrasion state of bit into eight steps for simulation cases and developed a forecast algorithm, i.e., TOSA which can analyze the depth and timing of round trip occurrence. A methodology that can divide a unit section for simulation has been suggested; while the Bourgoyne and Young model has been used for the forecast of drilling rates and bit abrasion extent by section. Lastly, the designed algorithm has been systemized for the convenience of the user.

• Tunnel and Underground Space
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• v.27 no.4
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• pp.230-242
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• 2017

Seismic velocities measured from in-situ tests (n=177) and through rock core samples (n=1,035) are reviewed in light of construction standards, widely used standards as a first-hand approximation of rock classification solely based on seismic velocities. In-situ down hole tests and refraction survey for soft rocks showed seismic velocities of 1,400~2,900 m/s which is faster than those specified in construction standards. For moderate~ hard rocks, in-situ down hole tests and refraction survey showed 2,300~3,800 m/s which roughly corresponds with the range specified in the construction standards. A similar trend is also observed for seismic velocities measured from rock core samples. The observed differences between construction standards and seismic velocities can be explained in two ways. If construction standards are correct the observed differences may be explained with seismic velocities affected by underlying fast velocities and also possibly with selection of intact cores for velocity measurement. Alternatively, construction standards may have intrinsic problems, namely artificial discrete boundaries between soft rocks and moderate rocks, application of foreign standards without consideration of geologic setting and lack of independent verification steps. Therefore, we suggest a carefully designed verification studies from a test site. We also suggest that care must be exercised when applying construction standards for the interpretation and accessment of rock mass properties.

• Tunnel and Underground Space
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• v.27 no.4
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• pp.217-229
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• 2017

This study focuses on the improvement of the working environment in domestic collieries where temperature is increasing due to heat of the earth that is caused by the long-term mining. In order to improve the working environment of the mine, a ventilation evaluation was carried out for Hwasoon Mining Industry. In order to increase the ventilation efficiency of the mine, numerical analysis of the effect on temperature was carried out by using climsim, a temperature prediction program. The analysis shows that A coal mine needs $6,152m^3/min$ for in-flow ventilation rate but the total input air flowrate is $4,710m^3/min$, $1,442m^3/min$ of in-flow ventilation rate shortage. The 93 m hypothetical ventilation shaft from -395 ML to -488 ML could result about $3^{\circ}C$ temperature drop in the coal mine of -488 ML far. As a result of predicting the $CO_2$ concentration at -523 ML development using artificial neural network, the emission of $CO_2$ increased as the amount of coal and coal bed thickness increased. The factors that have the greatest effect on the amount of $CO_2$ emissions were coal layer thickness and coal mining. And, as the air quantity increases, it has a great effect on the decrease of carbon dioxide concentration.