• Journal of the Korean Geophysical Society
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• v.5 no.3
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• pp.165-174
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• 2002

Seismic velocity and attenuation coefficient of the rocks under the broad-band earthquake observatories of the Korea Meteorological Administration have been measured in the laboratory by using very high frequency seismic waves. Estimated P velocities of the rocks range from 3.2 km/s to 5.6 km/s, depending on the rock type, mineral, and weathering, while, the attenuation coefficients vary from 0.06 to 4.3 db/kHz-m. It seems that P velocities is inversely proportional to the attenuation coefficients of the rocks. Average travel-time delays of the broad-band stations seem to be related with the measured P velocities in the laboratory.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.99-112
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• 1999

By using 92 values of lateral earth pressure coefficient(K) measured in Korea, the tendency of K with varying depth is analyzed and compared with the range of K defined by Hoek and Brown. The horizontal stress is generally larger than the vertical stress in Korea : About 84 % of K values are above 1. In this study, the theory of elasto-plasticity is applied to analyze the variation of K values, and the results are compared with those of numerical analysis. This reveals that the erosion, sedimentation and weathering of earth crust are important factors in the determination of K values. Surface erosion, large lateral pressure and good rock mass increase the K values, but sedimentation decreases the K values. This study enable us to analyze the effects of geological processes on the K values, especially at shallow depth where underground excavation takes place. A neural network expert system using multi-layer back-propagation algorithm is developed to predict the K values. The neural network model has a correlation coefficient above 0.996 when it is compared with measured data. The comparison with 9 measured data which are not included in the back-propagation learning has shown an average inference error of 20% and the correlation coefficient above 0.95. The expert system developed in this study can be used for reliable determination of K values.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.237-244
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• 2002

Televiewer is a logging tool capable of scanning the borehole wall. The tool uses a rotating acoustic beam generator that acts as both a transmitter and receiver. The beams are sent toward the wall. The amplitude of a returning signal from the wall has nearly a linear relationship with the reflection coefficient R of the borehole wall, when the wall is smooth. As R depends only on rock impedance for fixed water impedance, the amplitude is directly associated with mass density and seismic velocity of rock. Meanwhile, the amplitude can be further reduced by wall roughness that may be caused by drilling procedures, differences in rock hardness, because the rough surface can easily scatter the acoustic energy and sometimes the hole becomes elongated in all directions according to the degree of weathering. In this sense, the amplitude is related to the hardness of rocks. For convenience of analysis, the measured amplitude image(2-D data(azimuth ${\times}$ depth)) is converted, with an appropriate algorithm, to the 1-D data(depth), where the amplitude image values along a predetermined fracture signature(sinusoid) are summed up and averaged. The resulting values are subsequently scaled simply by a scalar factor that is possibly consistent with a known strength. This scaled Televiewer reflectivity is named, as a matter of convenience,“Televiewer rock strength”. This paper shows, based on abundant representative case studies from about 8 years of Televiewer surveys, that Televiewer rock strength might be regarded, on a continuous basis with depth, as a quitely robust indicator of rock classification and in most cases as an approximate uniaxial strength that is comparable to the rebound value from Schmidt hammer test.

• Journal of Environmental Health Sciences
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• v.32 no.2 s.89
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• pp.111-117
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• 2006

Polybrominated diphenyl ethers (PBDEs) in pine needles and soil samples from rural area were analyzed in this study. Concentrations of PBDE congeners were ranged between 0.2 and 3104 pg/g DW(dry weight) in pine needles and between 2.4 and 1997 pg/g DW in soil samples. The most abundant congener both in pine needles and soil samples was BDE-209, which was related to importation and production of deca-BDE technical mixtures in Korean industry. And BDE-99, BDE-47, BDE-100 deposited in pine needles and soil samples were closely matched with the major constituents of the penta-BDE technical mixture. Those can be interpreted as an evidence that transfer of the congeners in deca-BDE and penta-BDE technical mixtures from source to pine needle and soil occurs with broadly similar efficiency. Correlation coefficient(r) of PBDE congeners deposited in pine needles and soil samples is very significant because it implies th at there has been little weathering/degradation/alteration of the congeners generated from sources during atmospheric transport or within pine needles and soil themselves.

• Korean Journal of Heritage: History & Science
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• v.45 no.1
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• pp.86-101
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• 2012

The constituting rocks of Multi-storied Round shape stone Pagoda of Unjusa Temple are lithic tuff and rhyolite tuff breaccia which show green or grey and also rock fragment with poor roundness are present in the structure. lithic tuff is composed of feldspar and quartz which are glassy texture and cryptocrystalline and also micro crystalline are scattered. phenocryst quartz and feldspar in the substrate composed of feldspar and opaque minerals are found in rhyolite tuff breaccia. dust, exfoliation, cavity, fracture and crack are observed in all the stone of the pagoda and the result of Infrared Thermography shows partial inter cavities have developed severely which may cause further exfoliation. In addition, a great deal of various grey, green, and yellow brown lichen as well as bryophyte are present at the upper part of eastern and western roof stone located above the third floor. Discolors remarkably shown at stereobate and roof stone are identified as inorganic pollutants such as manganese oxide, iron oxide and iron hydroxide. The stone of the pagoda of the Chemical Index of Alteration (CIA) and the Weathering Potential Index (WPI) are 55.69 and 1.12 respectively and this corresponds to a highly weathered stage. The measured values, average ultrasonic velocity 2,892m/s, coefficient of weathering 0.4k and compressive strength $1,096kg/cm^3$, suggest that the rock strength and durability are weakened.

• Geotechnical Engineering
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• v.10 no.4
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• pp.5-16
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• 1994

This paper is concerned with the engineering characteristics weathered mudstone soil in Pohang area. The crushability of weathered Boil can be described in terms of the ratio of surface area(Sw'/Sw). In this study, the characteristics of weathered mudstone soil was investigated by performing teat such as compaction. CBR, permeability, and grain size according to compaction energy. The results are found as follows : (1) In generally, the specific gravity of weathered mudstone soil is very small and optimum moisture content (OMC) is large and maximum dry density is small (2) The CBR value increases as the compaction energy increases, but this value decreses from D -2 compaction(26kg.cm/cm3). the swelling ratio increases the npaction energy to 20.6kg.cm/cm" and decreases in all compaction energy from 20.6kg.cm/cm3 (3) As the compaction energy is small, the change of permeability due to water content is large and the difference between minimum coefficient of permeability and coefficient of permeability at OMC is large, but the difference is small as the compaction energy increases (4) The decrease of permeability due to the decrease of void ratio and the increase of ratio of surface area is caused by the crush of particle due to the increase in compaction energy. Especially, the compaction energy is smaller, the change of the ratio of surface area to the coefficient of permeability is larger.rger.

• Magazine of the Korean Society of Agricultural Engineers
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• v.18 no.4
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• pp.4218-4225
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• 1976

To insure the safety of the drainage sluice, topogrophical change due to erosion as well as capability of discharging the design flow in a very important factor. In consideration of the fact that the drainage sluice is built in the sea, its construction has many topographically restricted problems and naturally requires a completeness of research and experiment. This thesis is a comparative and analytic study of discharging flow acting on the erosion at the bottom of the structure on the basis of the measured velocity on the downstream channel of the drainage sluice. (1) The measured velocity shows a little higher values than the computed velocity, because the measured velocity was observed at the surface of the stream. There fore, it is reasonable that the compated velocity should be taken in this study. (2) The field observation was conducted to have the measurement of the flow velocity without surveying the area of flow. Therefore, the coefficient of discharge could not be computed. The survey of the area of flow is planned to be conducted along with the measurement of the flow velocity. (3) The apron of the drainage sluice is free discharging type and it was designed to be about 80m in length less than it should be. (4) The apron of free flow discharging type should have a solid foundation to protect the structure by preventing erosion damage to upstream and downstream channels against weathering of rock and strong torrent. Whether free flow discharging type or energy-dissipating type is best chosen depends on the topographical condition of the forage site, therefore, there would be a comparative study before the final decision was made about the protrection for the structure. (5) It is considered to be appropriate that the design and construction of the drainage sluice should have a complete study which is based on hydraulie model test before the type of protection is decided. (6) It is much requested that a variety of experiment equipments be installed and observed to study the protection for the drainage sluice.

• International Journal of Highway Engineering
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• v.15 no.1
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• pp.1-9
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• 2013

PURPOSES: The purpose of this study is to evaluate physical properties, durability, fatigue resistance, and long-term performance of poly-urethane concrete (PU) which can be possible application of thin layer on long-span orthotropic steel bridge and to check structural stability of bridge structure. METHODS : Various tests of physical properties, such as flexural strength, tensile strength, bond strength and coefficient of thermal expansion tests were conducted for physical property evaluation using two types of poly urethane concrete which have different curing time. Freezing and thawing test, accelerated weathering test and chloride ion penetration test were performed to evaluate the effect of exposed to marine environment. Beam fatigue test and small scale accelerated pavement test were performed to assess the resistance of PU against fatigue damage and long-term performance. Structural analysis were conducted to figure out structural stability of bridge structure and thin bridge deck pavement system. RESULTS: The property tests results showed that similar results were observed overall however the flexural strength of PUa was higher than those of PUb. It was also found that PU materials showed durability at marine environment. Beam fatigue test results showed that the resistances of the PUa against fatigue damage were two times higher than those of the PUb. It was found form small scale accelerated pavement test to evaluate long-term performance that there is no distress observed after 800,000 load applications. Structural analysis to figure out structural stability of bridge structure and thin bridge deck pavement system indicated that bridge structures were needed to increase thickness of steel deck plate or to improve longitudinal rib shape. CONCLUSIONS: It has been known that the use of PU can be positively considered to thin layer on long-span orthotropic steel bridge in terms of properties considered marine environment, resistance of fatigue damage and long-term performance.

• Tunnel and Underground Space
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• v.13 no.1
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• pp.6-19
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• 2003

This study has for its object to increase an objectivity of the observation result in the face mapping of tunnel and to suggest the reasonable support and reinforcement methods to be considered the rock properties. It was developed in this study to the tunnel stability evaluation system(Prototype NFEST) to be used fuzzy set theory and neuro-fuzzy techniques, and this system was verified according to the reliability evaluation between the 36 learning data and the inferred results. When it summarized the results; (1) 12 evaluation items and ranges were proposed to be modified basis on the RMR which are well known to the domestic workers. (2) It was shown that correlation coefficient(│R│) between $RMR_{inf}$ inferred by 12 items and $RMR_{org}$ due to arithmetic total, $RMR_{chk}$ due to subjective judgement of observer are relatively high relationship with each 0.83 and 0.79. (3) Inferred result of the total tunnel safety shows also a good relationship with $RMR_{inf}$ (│R│=0.7) and the rock weathering(│R│=0.84).

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.149-155
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• 2008

The road construction, as part of effort to ease the worsening traffic, has been underway throughout the nation, while the existing road has been increasingly losing its load carrying capacity due to such factors as heavy traffic and weathering. In the case of site, the soil type, plasticity index, and specific gravity were SC, 12.2%, and 2.66, respectively. The maximum dry density, optimum moisture content and modified CBR were $1.895g/cm^3$ (Modified Compaction D), 13.6%, and 16.2%, respectively. A correlation of coefficient expressed good interrelationship by 0.90 between the CBR estimated from a dynamic penetration index of dynamic cone penetrometer test and a deformation modulus converted from a dynamic deflection modulus obtained from a portable FWD test.