• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.815-822
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• 2004

A knowledge of in situ stress state is important to design various engineering structures such as dams, tunnels and so on. There are about three wellknown indicators that is, borehole will breakouts, hydraulic fracturing, ellipsoidal cross section of borehole that have been attributed to the state of stress in the vicinity of borehole. Fortunately, Televiewer traveltime image can be used as a caliper log with 144 or 288 arms, which allows to determine the borehole shape. Televiewer amplitude image will give detailed information about the distribution and character of breakouts and hydraulic fracturing as well. For investigation purposes, a series of boreholes(total 195 boreholes: 12.239m) that have been logged all over the country during past 10 years are analyzed. The primary objective of this paper are to examnine the ability of a Televiewer to determine the shape of borehole, to present data inferred by stress indicators, to indicate their possible relationship with the anisotropic horizontal stresses. It is shown that in most cases the fracture orientation statistically estimated from observed fractures denotes an excellent correlation with the orientations inferred by stress indicators. Many intervals of breakouts are terminated at the intersection of oblique fracture with the borehole. The results from Televiewer data are further compared with those of hydraulic fracturing techniques.

• The Journal of Engineering Geology
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• v.10 no.3
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• pp.225-236
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• 2000

We conducted laboratory simulations of deep vertical drilling into the earth's crust to induce borehole breakouts and investigated their potential use for estimating in situ stress magnitudes in Westerly granite and Berea sandstone. Our experiments consisted of two major stages, a series of triaxial tests and borehole-breakout formation tests under a wide range of far-field stresses. We derived the Mohr-Coulomb, Nadai and Mogi failure criteria from the triaxial test results. Each criterion was compared with the stress condition at breakout boundaries. We concluded that the well known Mohr-Coulomb criterion is not compatible with the stress condition at breakout failure. On the other hand, polyaxial (truly triaxial) failure criteria such as the Nadai criterion for Berea sandstone and the Mogi criterion for Westerly granite were much more suitable for predicting breakout failure zone. Such failure criteria appeared to enable the reliable estimation of the magnitude of one of two horizontal principal stresses if the other one is known.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.2_2
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• pp.219-224
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• 2020

This study is based on the principle of solar power system and fire breakout. The result of the survey indicates that a solar power system is vulnerable to fire due to lack of maintenance after the installation. Currently the national fire safety agency does not have standards and legal provisions for the installation and maintenance of solar power facilities. Therefore, it increases the risk of fire breakouts as well as possibility of electric shock for the firefighters during fire fighting. This results possible damages to the human and equipments. In this study is proposing an automatic fire extinguishing system to reduce the power generation of solar panels during fire breakouts. Also, propose an over load current alarm system and fire prevention measures for fire fighters. The results of this study will be used as basic data for further fire testing of solar power systems.

• Geomechanics and Engineering
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• v.24 no.3
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• pp.281-293
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• 2021

Uncertainties in geomechanical input parameters which mainly related to inappropriate data acquisition and estimation due to lack of sufficient calibration information, have led wellbore instability not yet to be fully understood or addressed. This paper demonstrates a workflow of employing Quantitative Risk Assessment technique, considering these uncertainties in terms of rock properties, pore pressure and in-situ stresses to makes it possible to survey not just the likelihood of accomplishing a desired level of wellbore stability at a specific mud pressure, but also the influence of the uncertainty in each input parameter on the wellbore stability. This probabilistic methodology in conjunction with Monte Carlo numerical modeling techniques was applied to a case study of a well. The response surfaces analysis provides a measure of the effects of uncertainties in each input parameter on the predicted mud pressure from three widely used failure criteria, thereby provides a key measurement for data acquisition in the future wells to reduce the uncertainty. The results pointed out that the mud pressure is tremendously sensitive to UCS and SHmax which emphasize the significance of reliable determinations of these two parameters for safe drilling. On the other hand, the predicted safe mud window from Mogi-Coulomb is the widest while the Hoek-Brown is the narrowest and comparing the anticipated collapse failures from the failure criteria and breakouts observations from caliper data, indicates that Hoek-Brown overestimate the minimum mud weight to avoid breakouts while Mogi-Coulomb criterion give better forecast according to real observations.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.60
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• pp.23-36
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• 2000

A probabilistic model of burr formation in face milling of gray cast iron is proposed. During a face milling operation, an irregular pattern of the edge profile consisting of burrs and edge breakouts is observed at the end of cut. Based on the metal cutting theory, we derive a probabilistic model. The operational bayesian modeling approach is adopted to include the relevant theory in the model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.181-185
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• 2001

Three-dimensional finite-element-based numerical model of turbulent flow, heat transfer, macroscopic solidification and inclusion trajectory in a continuos steel slab caster was developed Turbulence was incorporated using the Improved Low-Re turbulence model with positive preserving approach. The mushy region was modeled as the porous media with average effective viscosity. A series of simulations was carried out to investigate the effects of the casting speed, the slab size, the delivered superheat the immersion depth of the SEN on the transport phenomena. In the absence of any known experimental data related to velocity profiles, the numerical predictions of the solidified profile on a caster was compared with breakouts data and a good agreement was found.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.584-590
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• 2009

One of the critical design problems involved in deep tunnelling in brittle rock, is the creation of surface spalling damage and breakouts. If weak fault zone is developed in deep tunnel, squeezing problem is added to the problems. According to the results of ground investigation in the study area, hard granitic rockmass and distinguished high angle fault zone are distributed on the tunnel level over 400m depth. To analyse the probability of brittle failure and squeezing, ground characterization with special lab. and field test were carried out. By the results, probability of brittle failures like spalling and rock burst is very low. But squeezing may be probable, if weak fault zone observed surface and drill core is extended to designed tunnel level.

• Korean Journal of Health Education and Promotion
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• v.19 no.1
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• pp.87-107
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• 2002

Recently, the industrialized world is suffering from accidents referring from the lack of safety consciousness. According to Korean Safety Regulation Department(1996), students at junior high schools are mostly involved in safety accidents, and this is due to lack of safety consciousness. To prevent these accidents, we need to have safety consciousness and attitude. To make junior high school students who are mostly affected in these accidents act safely, they need to know their level of safety consciousness. The purpose of this study is to develop a guideline of measuring the scale of safety consciousness and analyze the relationship between safety education, accident experiences and safety consciousness. This study is based on a survey of 708 junior high students in Seoul, which was carried out from 12 November, 2001 to 21 November, 2001. 1. The main fields of safety consciousness are home safety, school safety, fire safety, emergency management based on documents. Home safety is again divided into facility safety and livelihood safety, school safety is divided into facility safety, livelihood safety and laboratory safety, traffic safety is divided into pedestrian safety, bicycling safety and public transportation safety, fire safety divided into prevention and escaping during fire breakouts, emergency management safety is divided into general principles and escaping during emergency situations. 2. The primary safety consciousness scale was made according to every field of safety consciousness. A preliminary examination based on the scale and a study of reliance and the factors was held. Based on these results, 27 questions which were concerned to be impairing reliability or lacking in factor were deleted on the secondary safety consciousness scale development The secondary safety consciousness scale which constituted of 73 questions was put into another preliminary study and after analyzing reliability and the factors, 12 questions of low reliabilities were deleted and with these results, the third scale were made consisting of 61 questions. 3. A study based on the third safety scale which is made of 61 questions, were held and with a analysis of the reliability and factors made, the relationship between safety education, accident experience and safety mind were examined. (1) The study of reliability and factors show that Cronbach's coefficient in home safety fields is .7598, in school safety .7924, in traffic safety .8306, in emergency treatment .7775, in fire safety .7247. The questions indicating low reliability were deleted. The factor analysis revealed that home safety is converged on facility safety and livelihood safety. But one question was deleted because it showed incongruence of validity. School safety was converged on facility safety, livelihood safety and laboratory safety. But 2 questions showed incongruence of validity and these were deleted. Traffic safety fields were converged on pedestrian safety, bicycle safety and public transportation safety. One question showing incongruence of validity was deleted. Emergency treatment fields converged on general principles and acting in emergency situations and three questions showing incongruence of validity were deleted. Fire safety was converged on prevention and acting in fire breakouts. Totally, eight questions were removed and the final scale were consisted of 53 questions (2) The 3/sup rd/ grade students scored higher average safety mind scales than 1st graders(p〈.05). And students who had high scores at school tend to have a higher scale than those who do not(p〈.001). (3) Average scale of students who had experience in safety education were higher(p〈.001). Students who had previously been involved in home safety accidents had a low score(p〈.001). This was same to students with experience in school safety accidents(p〈.001). Students with traffic safety accidents and fire safety accidents tend to have a lower scale too(p〈.05, p〈.001).

• Journal of KIISE:Software and Applications
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• v.29 no.11
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• pp.809-817
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• 2002

This paper describes a new face detection method that is a pre-processing algorithm for on-line face recognition. To complement the weakness of using only edge or rotor features from previous face detection method, we propose the two types of face detection method. The one is a combined method with edge and color features and the other is a center area color sampling method. To prevent connecting the people's face area and the background area, which have same colors, we propose a new adaptive edge detection algorithm firstly. The adaptive edge detection algorithm is robust to illumination variance so that it extracts lots of edges and breakouts edges steadily in border between background and face areas. Because of strong edge detection, face area appears one or multi regions. We can merge these isolated regions using color information and get the final face area as a MBR (Minimum Bounding Rectangle) form. If the size of final face area is under or upper threshold, color sampling method in center area from input image is used to detect new face area. To evaluate the proposed method, we have experimented with 2,100 face images. A high face detection rate of 96.3% has been obtained.

• Geophysics and Geophysical Exploration
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• v.1 no.1
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• pp.31-42
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• 1998

Recently crosshole seismic tomography has come to be widely used especially for the civil engineering, because it can provide more detail information than any other surface method, although the resolution of tomogram will be inevitably deteriorated to some extent due to the limited wavefield aperture on the nonuniqueness of traveltime inversion. In addition, our field sites often consist of a high-velocity bed rock overlain by low-velocity rock, sometimes with a contrast of more than 45 percent, and furthermore the bed rock is folded. The first arriving waves can be then the refracted ones that travel along the bed rock surface for some source/receiver distances. Thus, the desirable first arrivals can be easily misread that cause severe distortion of the resulting tomogram, if it is concerned with (straight ray) traveltime inversion procedure. In this case, comparision with synthetic data (forward modeling) is a valuable tool in the interpretation process. Besides, abundant information is contained in the crosshole data. For instance, examination of tube waves can be devoted to detecting discontinuities within the borehole such as breakouts, faults, fractures or shear zones as well as the end of the borehole. Specific frequency characteristics of marine silty mud will help discriminate from other soft rocks. The aim of this paper is to present several strategies to analyze and interpret the crosshole data in order to improve the ability at first to determine the spatial dimensions of interwell anomalies and furthermore to understand the underground structures. To this end, our field data are demonstrated. Possibility of misreading the first arrivals was illustrated. Tube waves were investigated in conjunction with the televiewer images. Use of shot- and receiver gathers was examined to benefit the detectabilities of discontinuities within the borehole.