• Tunnel and Underground Space
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• v.33 no.6
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• pp.561-573
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• 2023

Korea Atomic Energy Research Institute (KAERI) constructed the KURT (KAERI Underground Research Tunnel) to analyze the hydrogeological/geochemical characteristics of deep rock mass. Numerous boreholes have been drilled to conduct various field tests. The selection of suitable investigation intervals within a borehole is of great importance. When objectives are centered around hydraulic flow and groundwater sampling, intervals with sufficient groundwater flow are the most suitable. This study defines such points as hydraulic outliers and aimed to detect them using borehole geophysical logging data (temperature and EC) from a 1 km depth borehole. For systematic and efficient outlier detection, machine learning algorithms, such as DBSCAN, OCSVM, kNN, and isolation forest, were applied and their applicability was assessed. Following data preprocessing and algorithm optimization, the four algorithms detected 55, 12, 52, and 68 outliers, respectively. Though this study confirms applicability of the machine learning algorithms, it is suggested that further verification and supplements are desirable since the input data were relatively limited.

• 기술발표회
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• s.2006
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• pp.199-209
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• 2006

현재 연약지반의 개량 및 구조물기초 지반의 보강을 위하여 약액주입공법 및 고압분사주입공법 등의 주입공법이 널리 행해지고 있는 실정이다. 이에 본 연구에서는 00교 교대 전면 옹벽기초 하부지반을 고압분사주입공법을 이용해 보강한 사례로서 설계 및 시공, 시험 자료를 분석하고, 보강작업에 따른 지반의 개량효과를 분석하였다. 개량효과학인을 위한 시추조사와 시추공영상 촬영 이미지 관찰결과에서는 고압분사에 의해 양호한 상태의 고결체(토사 + 시멘트 페이스트)가 형성되었음을 확인 할 수 있었으며, 고결체와 원지반의 복합지반상에서 실시한 평판재하시험 결과 및 시추조사시 채취된 고결체 Core에 대해 실시한 일축압축강도시험 결과에서도 설계시 가정한 값을 모두 만족하는 것으로 나타나 연약지반의 강도가 개량되어 안정성을 확보한 것으로 확인되었다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.4
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• pp.257-263
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• 2008

We analyzed the statistical properties for the conductive background fractures in the Low and Intermediate Level Waste(LILW) disposal site to conceptualize of its groundwater flow system. The background fractures were classified to fracture sets based on their trends and plunges that were obtained from the borehole logging data, and then the fracture transmissivity distribution was inferred from the fixed interval hydraulic test results. The fracture size distribution of each fracture set was estimated using the fracture density and fracture mapping data. To verify the analyzed results, we compared observed field data to simulated one from the DFN model that was constructed with the analyzed statistical properties of the background fractures, and they showed a good agreement.

• The Journal of Engineering Geology
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• v.12 no.2
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• pp.127-135
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• 2002

The relationship between the seismic velocity and RQD was estimated using the RQD data obtained from the optical borehole image processing and drill core logs and the seismic velocity measured from the PS logging. The seismic velocity and crack aperture show a high correlation in the granite in Yuseong area and banded gneiss in Paldang area. However, such a relationship cannot be found in the sedimentary rock in Sabuk area. In the sedimentary rock of Sabbuk area, the seismic velocity shows widespread distribution especially in the 0∼20mm range of accumulated crack aperture probably because the wide distribution of fracture zone in coaly shale results in the inaccurate measurements of the crack aperture.

• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.53-60
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• 2014

There have been vast amounts of the site investigation data from the domestic construction sites every year and various national research institutes are constructing the database for the site investigation data. According to the Ministry of Land, Transport and Maritime Affairs, the database for the site investigation has been constructed for covering 154,000 individual boreholes since the computerization project for the geotechnical information started at 2000. It is considered to be high time to evaluate the reliability of the stored DB so that the current DB should be utilized to the various fields related to the planning and site investigation of the construction activities. Therefore, the precision of the stored site investigation data was evaluated via normal distribution for more active sharing and utilization. As a preliminary evaluation of the precision, the locations of the encountered strata from two different sites were analyzed. After the precision of the stored data is determined, the level of reliability of the each category of the stored geotechnical information would be determined and the users would be able to decide which information could be utilized.

• Tunnel and Underground Space
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• v.26 no.4
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• pp.304-315
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• 2016

In this study, the current horizontal stress characteristics of the Tertiary rock formations in the Pohang Basin are investigated on the basis of the in-situ rock stress measurements at depths from 75 m to 716 m of the 3 test boreholes in the Doumsan area, Pohang. The deep hydraulic fracturing stress measurement results indicated that the horizontal stress components in the test site appear far lower than the average ones by the linear fit for the data set measured from the other domestic sites. But, borehole scanning revealed clearly that lots of small and large scale borehole failures occurred due to the low strength characteristics of the existing rocks. To obtain more accurate and overall information on the horizontal stress direction, the integrated analysis combining the hydraulic fracturing stress measurement and borehole scanning data set were additionally carried out. The analysis results showed that in the upper sedimentary and the lower volcanic rock formation, the dominant orientations of the current maximum horizontal stress components were appeared in the range of $80^{\circ}{\sim}100^{\circ}$ (N80E~N80W) and $120^{\circ}{\sim}140^{\circ}$ (N60W~N40W), respectively. From this study result it was found that the maximum horizontal stress directions have a tendency to rotate in a clockwise direction as the rock formation changes with depth in the test site.

• The Journal of Engineering Geology
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• v.22 no.4
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• pp.409-416
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• 2012

In this study, an electrical resistivity survey and a drilling investigation were conducted at an animal carcass disposal site. Chemical analysis of leachate collected from the site was also performed (sampling times: May 2011 and June 2012). Five lines of dipole-dipole electrical resistivity surveys were carried out, along with drilling investigations at 3 points within the disposal areas and 11 points near the disposal site. Two-dimensional inverse modeling of the collected resistivity data was performed to evaluate the properties (size, depth, and form) of the disposal site. Leachate analysis showed that pH of leachate decreased from 7.4 to 6.7, while Eh changed from -358 mV to -48 mV over time. In addition, dissolved ions increased due to the progression of carcass decomposition. Results of the electrical resistivity survey indicated that low resistivity zones (minimum value, $0.64{\Omega}m$) existed at a depth of 8 m from the surface. Considering the bedrock location and carcass disposal depth, there was no evidence of bedrock contamination by leachate. The results of the electrical resistivity survey are consistent with those of the drilling investigation, which indicates that electrical resistivity effectively depicted the properties of the disposal site. This study demonstrates that electrical resistivity survey is a suitable technique for investigation of animal carcass disposal sites.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.323-330
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• 2017

For the formation identification, surface geological survey, drill core analysis, core description and well log analysis are widely used. Among them well log analysis is a popular method with drill core analysis, since it measures continuously physical properties at in-situ. In this study we calculated Thomsen anisotropic parameters (${\varepsilon},\;{\delta},\;{\eta}$) after applying Backus averaging method to the P wave velocity, S wave velocity, and density logs. The well log data application of Blackfoot, Canada, shows the formation could be divided by 12 layers. This shows that Thomsen anisotropic parameters for identifying formation using anisotropic parameters is useful if there is no natural gamma log that is widely used for the formation identification.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.242-251
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• 2013

Recently, while global concern over offshore resources exploration and development is being increased rapidly, offshore plant industry is highlighted as an industry of high added value. Along with this global trend, domestic concern over offshore plant development is being increased as well. In the overseas case, a marine geotechnical survey guideline for confirming characteristics of seabed sediments is available at the time of installation of offshore plant but such guideline is not available in our country. In this study, survey techniques fit for domestic marine environment was applied according to overseas guideline at southern coastal area, Korea. Among the marine geophysical survey techniques being proposed abroad, magnetic survey and seabed photograph were excluded. However, highly reliable data analysis was enabled for marine geophysical survey, which includes in-situ coring investigation and laboratory soil test. In addition, continuous ocean current survey was included to find scour potential due to the current around the offshore plant. Although coring depth is not so deep, we predicted geological structure through the analysis of amplitude features of seismic data. Characteristics of seabed sediments cold be obtained regionally and directly through combined analysis of marine geophysical survey data and coring data.

• Tunnel and Underground Space
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• v.13 no.1
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• pp.33-43
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• 2003

Field investigations of the orientations of discontinuity planes inside the borehole for designing the underground rock structures have been depend solely on the borehole image-taking techniques. But, borehole image-taking has to be processed after the completion of drilling operation and also requires the handling of highly expensive apparatus so that practical application is very restricted. In this study Discontinuity Orientation Measurement (DOM) drilling system and discontinuity analysis model RoSA-DOM are developed to acquire the reliable information of rock structure by analyzing the characteristics of joint distribution. DOM drilling system retrieves the rock core on which the reference line of pre-fixed drilling orientation is engraved. Coordinates of three arbitrary points on the joint surface relative to the position of reference line are assessed to determine the orientation of joint plane. The position of joint plane is also allocated by calculating the location of core axis at which joint plane is intersected. Then, the formation of joint set is analyzed by utilizing the clustering algorithm. Total and set spacings are calculated by considering the borehole axis as the scanline. Engineering applicability of in-situ rock mass around the borehole is also estimated by calculating the total and regional RQDs along the borehole axis.