• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.839-848
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• 2011

TBM (Tunnel Boring Machine) tunnel should be carry out with the adopted machine until the end of excavation because of impossibility of replacement or modification of machine. Observation of the face of the tunnel is difficult, especially in EPB(Earth Pressure Balance) shield TBM, predict changes in the ground condition with analyzing data, collected during the excavation, and it should be reflected in construction. Until recently, subjects of studies on TBM are mainly the determination of machine and the development of advance rate prediction model, according to the characteristics of ground which is the target of excavation. However, study focused on the estimation of ground conditions and the improvement in operational methods using excavation data of TBM equipment, the principal of the excavation, has been done not so much. This study examine the variances in advance rate depending on changes in operating conditions and evaluate the optimal operating conditions of adopt machine, using working data obtained from EPB shield TBM project. The result of this study is suggested as follows. First, cutter head RPM and total thrust force are biggest influences on advance rate, Second, it is recommended for proper advance rate that total thrust force is controlled while optimum cutter head RPM is kept, Third, according to the increasing trend of total thrust force, the changes in ground conditions can be predicted, the appropriate operating conditions can be determined.

• The Journal of Engineering Geology
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• v.14 no.3 s.40
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• pp.301-311
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• 2004

This study is suggested a new dielectric tracer test method to understand geological structure of porous media and groundwater flow to use the dielectric constant which is one of electrical special quality of various geological materials. To measure their parameters, tracer material is made an ethanol mixing liquid(EML) having a same specific gravity of water. Also, soil materials are prepared a dielectric tracer test using the FDR system that could measure dielectric constant for saturated standard sand and river sand layers which have different initial porosity. To compare with their results, we discussed with the concentration variation of saline water having a saline concentration $3\%$ which is general tracer material by using the electro multi-meter system in the laboratory or field test. In two tracer experiment results, EML tracer test could confirm definitely EML concentration variation from each saturated soil layer as standard and river sands. However, tracer test of saline water $3\%$ concentration could not confirm permeating movement of water by degree of salinity change because these are settled at lower part column in a whole column area continuously. These causes are that specific gravity of saline water is heavier than water. That is, it could know that deposition of saline water is composed of lower part of soil column continuously independently of the direction of water into saturated soil material.

• Journal of Korean Philosophical Society
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• v.137
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• pp.383-407
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• 2016

Considering the long time that modern man has been autonomous, it can be said that the brutal human violence prevalent around the globe today is an 'exceptional situation'. Behavior such as killing animals or devastating the natural environment are thought to be unavoidable. However, if human beings have been 'social animals' pursuing connectedness and seeking meaning in the relationships of others beyond themselves since the beginning of time, how can the incredibly powerful violence which humankind has inflicted on plants, other animals, or the earth itself be explained? With this in mind, I propose the following arguments. First, the crisis of consciousness in the loss of hope for the future of mankind under the technology of modern Western civilization has already come to a dead-end causing Western philosophers to think of ways to discover new opportunities, apparent as ecology and ecological philosophy. Second, as reality has become governed by the technology of modern Western civilization and ecological philosophical rationality fails to co-exist with this reality, an understanding of ecological philosophy should be deepened and continued. In this context, I will investigate the existential conditions for human life to continue in the future in consideration of ecological philosophy and the meaning of Forest.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.619-630
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• 2018

The purpose of this study is to investigate the existence of faults and intrusive rocks in the volcanic rock mass of Ulleung-do using magnetic anomalies. The magnetic survey data show that basaltic (mafic) rocks have high magnetic anomalies and that trachytic (felsic) rocks have low magnetic anomalies, implying that the anomaly distributions can be used to distinguish between different volcanic rock types that may be covered by regolith (such as alluvial and colluvial deposits) and other sedimentary layers. Our results show that basaltic rocks are not present within the Nari caldera. However, outside the caldera, the occurrence of high magnetic anomaly values of >$1,000{\gamma}$ is presumed to reflect the existence of basaltic craters or volcanic vents that formed prior to the eruption of the trachytic rocks. In particular, the area with anomaly values of >$1,000{\gamma}$ in the vicinity of Namyang-ri, southwest of Ulleung-do, is interpreted as having a high probability of hosting a crater and vent originating from mafic volcanism.

• Journal of the Korean Geophysical Society
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• v.4 no.1
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• pp.57-69
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• 2001

We have carried out a nondestructive close examination for the purpose of the structural safety diagnosis of the Three-Story Pagoda(Seokga Pagoda) in Bulkuk temple in the city of Kyungju, Kyungbuk, Korea. Ultrasonic wave velocities were measured at 456 points of the pagoda comprising 44 blocks to estimate the mechanical properties of rock blocks constituting the pagoda. The measured velocities have the range of 1217 to 4403 m/sec with the average of 3227 m/sec. The empirical relationship between the ultrasonic velocity and the uniaxial compressive strength yielded the estimation of strength of each block, ranging from 134 to 844 kg/cm^2 and averaging 463 kg/cm^2. With an assumption that the strength of each block is described as a random variables having a normal distribution, we calculated the probability of failure of rock blocks of the pagoda. Our investigation revealed that the probability of the structural failure due to the weight of higher blocks is very low. However, the probability of partial failure around contact area is substantial, which is consistent with the appearance that edges and the corners of some blocks were broken off. The platform under the body of the pagoda appeared to be structurally weak as the probability of tensile failure of the lower platform is up to 18%, and diagonal fractures are shown where the probability of failure is high.

• Journal of the Korean Geophysical Society
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• v.3 no.4
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• pp.269-280
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• 2000

Rail vibration in city zone is becoming a serious environmental problem. In order to make a reduction plan for rail vibration, the research was conducted in which many experiments to measure actual rail vibration along the railroad through the central Deajeon area. A digital vibration level meter was used to measure rail vibration. Vibration levels of Z-axis were measured at every second for the duration of the train passing. The measuring station was placed at every 5m for the distance of 55m. A total of 353 different sets of vibration level were obtained. The signals were processed to get $L_{10}$ value and analyzed in terms of distance, train velocity, and number of trains. As a result, it has been found that rail vibration exceed the allowable vibraton limit of 60 dB, at the point of 25 m far from the railroad center, which is regulated by the las of vibration and noise. Train velocity was found to affect a little for vibration level within the zone. It was also found that a trench installed along a railroad could reduce vibration level up to approximately 10 percent. A model test was conducted to investigate the influence of the location and size of trench, on the transfer of vibration. A heavy steel ball was used to generate vibrations. On the basis obtained from this study, it could be concluded that the application of distance-attenuation and the installment of a trench along railroad could be applied as a reduction plan for rail vibration. Because limitions might exist to depend on the effect of distance attenuation, trenchs excavated along a railroad might be suggested as the most efficient solution to reduce railroad vibration.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.1
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• pp.1-9
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• 2009

Export fluxes of particulate organic carbon were estimated for the first time by using $^{234}Th/^{238}U$ disequilibrium in the southwestern East Sea during August 2007. They were calculated by multiplying POC/$^{234}Th_p$ ratios of sinking particles (larger than 0.7 ${\mu}m$) obtained from 150-200 m water depths to $^{234}Th$ fluxes that were estimated by integrating $^{234}Th/^{238}U$ disequilibrium from surface to 100 m water depth. Export fluxes ranged from 14 to 505 mg C $m^{-2}$ $day^{-1}$, with the highest value at station A2 and the lowest value at station D4. Primary production was well correlated with export flux, indicating that it was a major factor controlling export flux. Export flux in the East Sea was generally higher than those estimated in the open ocean and similar to or somewhat higher than those in the continental marginal seas. Export flux/primary production (EF/PP) ratios varied from 0.29 to 0.62, with an average of 0.43 and were somewhat higher in the basin area than in the coastal area. EF/PP ratio in the East Sea was rather similar to those estimated in the North Sea and Chukchi Sea, but much higher than those in the Labrador Sea, Barents Sea, and Gulf of Lions. Therefore, the East Sea is one of the major areas where a large amount of organic carbon produced in the euphotic zone sinks into the deep layer below 200 m water depth.

• Journal of the Korean Geophysical Society
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• v.4 no.2
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• pp.103-111
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• 2001

Geophysical survey was carried out to derive some information on the existence of near-surface anomalous body at Reung-Chi area in Kongju. Resistivity, seismic, magnetic and gravity method were applied. Geophysical survey that was applied was the electrical resistivity survey, seismic survey, magnetic survey, gravity survey. These surveys are analyzed to provide data of high resolution. As a result of analysis of resistivity survey, anomalies showing high resistivity anomaly than around appeared, and the one showing M-shape out of those explains the possibility that underground common or other underground structure or geographical anomalous zone could exist in the underground. As a result of analysis of seismic survey, it is clear that the low velocity layer is spread as far as the bottom of the underground. It is possible to presume that it is a phenomenon appearing while going through the underground space where it is lying in the underground. Area that shows unusual situation in interpretation of data on seismic waves are included into the area that once showed resistivity anomaly, the results of both seismic surveys come in accord. As a result of magnetic survey, a circle-shape of twin magnetic fields in the area where abnormalities are shown between electrical resistivity survey and seismic survey is appeared. Given the area of gravity survey, abnormalities whose density is different from the one around the bottom of the underground. As a result of analogizing the data of underground of the subsurface based on analysis of data from each survey, it was interpreted that anomalous zone exists commonly in the research areas.

• Journal of the Korean Geophysical Society
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• v.5 no.3
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• pp.199-209
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• 2002

We have carried out a nondestructive close examination for the purpose of the structural safety diagnosis of the Dabo Pagoda of Bulkuk temple located in Kyungju, Kyungbuk Korea. For estimating the mechanical properties of each rock block of the pagoda, ultrasonic measurements were conducted at 641 points of 255 blocks. The P-wave velocity ranges from 584m/sec through 5,169m/sec, and averages 2,901m/sec Based on this result, the uniaxial compressive strength was estimated to be $93{\sim}1,943kg/cm^2\;with\;396kg/cm^2$ of average, and the index of weathering is $0.07{\sim}0.88$ with 0.43 of average, which means the moderate degree of weathering. The comparison of the rock strength of each block with the overburden acting on the block reveals that the rock blocks related to the structure of the pagoda are relatively sound for uniform stress, but it is highly possible for a concentrated stress to lead to a partial failure. We suggest a monitoring of cracks due to the concentrated stress. The parapets of 1st and 2nd floors composed of small rock pieces are severely weathered. However, this is not directly related to the structural safety of the pagoda.

• Geophysics and Geophysical Exploration
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• v.1 no.3
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• pp.176-182
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• 1998

The borehole radar reflection survey can image the underground structure with high resolution, however, we cannot get any information on the orientation of the reflectors with dipole antenna alone. The direction-finding antenna system is commonly used to give the solution to the problem. However, the interpretation of the data from direction- finding antenna may be time-consuming, and sometimes have ambiguities in the sense of precise determination of the azimuth. To solve the problem, we developed the automatic azimuth finding scheme of reflectors in borehole radar reflection data using direction-finding antenna. The algorithm is based on finding the azimuthal angle possibly showing the maximum reflection amplitude in the least-squared error sense. The developed algorithm was applied to the field data acquired in quarry mine. It was possible to locate nearly all of the reflectors in three dimensional fashion, which coincide with the known geological structures and man-made discontinuities.