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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of Engineering Geology
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Journal DOI :
The Korea Society of Engineering Gelolgy
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Volume & Issues
Volume 24, Issue 4 - Dec 2014
Volume 24, Issue 3 - Sep 2014
Volume 24, Issue 2 - Jun 2014
Volume 24, Issue 1 - Mar 2014
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Engineering Geological Characteristics of Freeze-Thaw Weathered Gneiss in the Wonju Area, Korea
Um, Jeong-Gi ; Woo, Ik ; Park, Hyuck Jin ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 161~169
DOI : 10.9720/kseg.2014.2.161
We present the results of an experimental physical weathering study that focuses on fresh and slightly weathered gneiss samples from the Wonju area of Korea. The study investigated changes in the physico-mechanical properties of these samples during accelerated laboratory-based weathering, including analyses of microfracture formation. The deteriorated samples used in the study were subjected to 100-150 freeze-thaw cycles, with index properties and microfracture geometries measured between each cycle. Each complete freeze-thaw cycle lasted 24 hours, and consisted of 2 hours of saturation in a vacuum chamber, 8 hours of freezing at
, and 14 hours of thawing at room temperature. Specific gravity and seismic velocity values were negatively correlated with the number of freeze-thaw cycles, whereas absorption values tended to increase. The amount of deterioration of the rock samples was dependent on the degree of weathering of the rock prior to the start of the analysis. Absorption, specific gravity, and seismic velocity values can be used to infer the amount of physical weathering experienced by a gneiss in the study area. The sizes and density of microfracture in the rock specimens varied with the number of freeze-thaw cycles. We found that box fractal dimensions can be used to quantify the formation and propagation of microfracture in the samples. In addition, these box fractal dimensions can be used as a weathering index for the mid-and long-term prediction of rock weathering. The present results indicate that accelerated-weathering analysis can provide a detailed overview of the weathering characteristics of deteriorated rocks.
Enhancement of Seismic Stacking Energy with Crossdip Correction for Crooked Survey Lines
Kim, Ji Soo ; Lee, Sun Jung ; Seo, Yong Seok ; Ju, Hyeon Tae ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 171~178
DOI : 10.9720/kseg.2014.2.171
In seismic reflection data processing, the crossdip correction effectively focuses the stacking energy near the sharp bends of a crooked survey line. Additionally, approximate 3-D information on the reflector (e.g., true crossdip angle and lateral continuity) are locally investigated as a by-product of the crossdip correction procedure. Improvement of the signal-to-noise ratio and estimation of reflector crossdip attitude are tested, in terms of both common midpoint bin direction and processing-line type, using synthetic seismic reflection data. To effectively image the reflection energy near bends in seismic survey lines, straight-line binning is preferred to slalom-line binning.
Identification and Three-Dimensional Characterization of Micropore Networks Developed in Granite using Micro-Focus X-ray CT
Choo, Chang-Oh ; Takahashi, Manabu ; Jeong, Gyo-Cheol ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 179~189
DOI : 10.9720/kseg.2014.2.179
We analyzed the three-dimensional distribution of micropores and internal structures in both fresh and weathered granite using micro-focus X-ray computed tomography (micro-CT). Results show that the pore radius in fresh granite is mostly in the range of
, the throat radius is in the range of
, and the coordination number (CN) of pores is less than 10. In contrast, the pore radius in weathered granite is mostly in the range of
, the throat radius is in the range of
, and the CN is less than 12. In general, a positive linear relationship exists between pore radius and CN. In addition, both the size and the density of pores increase with an increasing degree of rock weathering. The size of the throats that connect the pores also increases with an increasing degree of weathering, which induces fracture propagation in rocks. Micro-CT is a powerful and versatile approach for investigating the three-dimensional distributions of pores and fracture structures in rocks, and for quantitatively assessing the degree of pore connectivity.
Development of a Method for Detecting Unstable Behaviors in Flume Tests using a Univariate Statistical Approach
Kim, Seul-Bi ; Seo, Yong-Seok ; Kim, Hyeong-Sin ; Chae, Byung-Gon ; Choi, Jung-Hae ; Kim, Ji-Soo ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 191~199
DOI : 10.9720/kseg.2014.2.191
We describe a method for detecting slope instability in flume tests using pore pressure and water content data in conjunction with a statistical control chart analysis. Specifically, we conducted univariate statistical analysis on x-MR control chart data (pore pressure and water content) collected at several points along the flume slope, which we separated into three parts: upper, middle, and lower. To assess our results in the context of landslide forecasting and warning systems, we applied control limit lines at
levels of uncertainty. In doing so, we observed that dispersion time varies depending on the control limit line used. Moreover, the detection of instabilities is highly dependent on the position and type of sensor. Our findings indicate that different characteristics of the data on various factors predict slope failure differently and these characteristics can be identified by univariate statistical analysis. Therefore, we suggest that a univariate statistical approach is an effective method for the early detection of slope instability.
Analysis of the Correlation between Geological Characteristics and Water Withdrawals in the Laterals of Radial Collector Well
Kim, Tae-Hyung ; Jeong, Jae-Hoon ; Kim, Min ; OH, Se-Hyoung ; Lee, Jae-Sung ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 201~215
DOI : 10.9720/kseg.2014.2.201
This study was performed to investigate the correlation between hydraulic conductivity and the flow rate of an aquifer, with the flow rate calculated from the laterals of the radial collector well using data obtained by the development project of riverbank filtration (Second Phase) in Changwon City. The hydraulic conductivity was empirically calculated from unconsolidated sediments collected from a sandy gravel layer along the middle-to-downstream sections of the Nakdong River. The Beyer equation produced the most suitable hydraulic conductivity from the various empirical formulas employed. The calculated hydraulic conductivity ranged from 0.083 to 0.264 cm/s, with an average value of 0.159 cm/s, suggesting that the aquifer in the study area possesses a high permeability with a good distribution of sandy gravel. The relationship between the calculated hydraulic conductivity in the aquifer and the entrance velocity into the screen, the flow rate was analyzed through the linear regression analysis. From the result of regression analysis, it showed that the hydraulic conductivity and the entrance velocity into the screen and the flow rate have a linear regression equation having about 72% of the high correlation. The result of verification in the measured data between each variable showed a high suitability from being consistent with the approximately 72% in the linear regression analysis. This study demonstrates that the groundwater flow rate can be estimated within the laterals of the radial collector well using a linear regression equation, if the hydraulic conductivity of the aquifer is known. This methodology could thus be applicable to other aquifers with hydraulic conductivity and permeability parameters similar to those in the present study area.
Analysis of Groundwater Variations using the Relationship Between Groundwater use and Daily Minimum Temperature in a Water Curtain Cultivation Site
Chang, Sunwoo ; Chung, Il-Moon ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 217~225
DOI : 10.9720/kseg.2014.2.217
Water curtain cultivation (WCC) systems in Korea have depleted water resources in shallow aquifers through massive pumping of groundwater. The goal of this study is to simulate the groundwater variations observed from massive groundwater pumping at a site in Cheongweon. MODFLOW was used to simulate three-dimensional regional groundwater flow, and the SWAT (Soil and Water Assessment Tool) watershed hydrologic model was employed to introduce temporal changes in groundwater recharge into the MODFLOW model input. Additionally, the estimation method for groundwater discharge in WCC areas (Moon et al., 2012) was incorporated into a groundwater pumping schedule as a MODFLOW input. We compared simulated data and field measurements to determine the degree to which winter season groundwater drawdown is effectively modeled. A simulation time of 107 days was selected to match the observed groundwater drawdown from November, 2012 to March, 2013. We obtained good agreement between the simulated drawdown and observed groundwater levels. Thus, the estimation method using daily minimum temperatures, may be applicable to other cultivation areas and can serve as a guideline in simulating the regional flow of riverside groundwater aquifers.
Estimation of the Deformation Modulus for a Fault Zone using Crown Settlements Measured During Tunnel Excavation
Yun, Hyun-Seok ; Moon, Seong-Woo ; Song, Gyu-Jin ; Seo, Yong-Seok ; Kim, Ji-Soo ; Woo, Sang-Baik ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 227~235
DOI : 10.9720/kseg.2014.2.227
The deformation modulus is one of the essential factors in determining ground behavior and safety during tunnel excavation. In this study, we conducted a back-analysis using crown settlements measured during tunnel excavation, using a horizontal inclinometer on a fault zone of pegmatite, and calculated the deformation modulus of the fault zone. This deformation modulus calculation was then compared with deformation moduli found through established relationships that use the correlation between RMR and the deformation modulus, as well as the results of pressure-meter tests. The deformation moduli calculated by back-analysis differs significantly from the deformation moduli determined through established relationships, as well as the results from pressure-meter tests conducted across the study area. Furthermore, the maximum crown settlements derived from numerical analysis conducted by applying deformation moduli determined by these established relationships and the pressure-meter tests produced noticeable differences. This result indicates that in the case of a weak rock mass, such as a fault zone, it is inappropriate to estimate the deformation modulus using preexisting relationships, and caution must be taken when considering the geological and geotechnical characteristics of weak rock.
Contamination Characteristics of Agricultural Groundwater Around Livestock Burial Areas in Korea
Kim, Hyun Koo ; Park, Sun Hwa ; Kim, Moon Su ; Kim, Hye Jin ; Lee, Min Kyeong ; Lee, Gyeong-Mi ; Kim, So-Hyun ; Yang, Jae-Ha ; Kim, Tae Seung ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 237~246
DOI : 10.9720/kseg.2014.2.237
Seasonal variations of major contaminants in groundwater around livestock burial areas in Gyeonggi province, Korea, were examined. Seven typical contamination indicators (
-N, chloride, pH, DO, ORP, and EC) were monitored in groundwater samples collected from 84 wells located within 60 m of livestock burial sites for the leachate plume emanating from the livestock burial sites. The monitoring results of pH, DO, ORP, and EC revealed minimal seasonal variations, providing no evidence for leachate plumes. The
-N concentrations were below 30 mg/L and exhibited minimal seasonal fluctuations, even in the wells located close to (< 20 m) the burial sites; the
-N and chloride concentrations also showed similar results. The contamination indicators examined in this study indicate that the observed groundwater contamination is primarily from preexisting pervasive contamination due to agricultural activities and livestock farming, not leachates derived from nearby livestock burial sites.
Rock Mechanics Modeling of the Site for the 2
Step Construction of the KAERI Underground Research Tunnel (KURT)
Jang, Hyun-Sic ; Ko, Chi-Hye ; Bae, Dae-Seok ; Kim, Geon-Young ; Jang, Bo-An ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 247~260
DOI : 10.9720/kseg.2014.2.247
Rock masses at the site for the
step construction of the KAERI Underground Research Tunnel (KURT) are divided into six units to establish a rock mechanics model that is dependent on the geological characteristics and degree of joint development. The site primarily consists of three granitic units (G1, G2, and G3), two dykes (D1 and D3), and a fault zone of poor rock mass quality (F3). The F3 unit crosses the tunnel at the beginning of the site of
step construction. The rock masses of each unit are classified by RMR (Rock Mass Rating), Q-system, and RMi (Rock Mass Index), all based on borehole logging data. The deformation modulus, rock mass strength, cohesion, and friction angle for each unit are calculated using established empirical relationships. The representative rock mass classification and geotechnical parameters for the rock mass units are established, and a rock mechanics model for the site is proposed, which will be useful in the design and stability analysis of the
step construction of KURT.
A Study for the Applicable Bearing-Resistance of Bearing Anchor in the Enlarged-Borehole
Min, Kyoung-Nam ; Lee, Jae-Won ; Lee, Jung-Gwan ; Jung, Chan-Muk ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 261~271
DOI : 10.9720/kseg.2014.2.261
An almost permanent anchor (friction type) is resistant to ground deformation due to the friction between the soil and grout at a fixed length from the anchor body. The purpose of this study is to calculate the force of bearing resistance for a bearing anchor in enlarged boreholes. We conducted analytical and numerical analyses, along with laboratory testing, to find the quantities of bearing resistance prior to grouting in EBA (Enlarged Bearing Anchor) construction. The force of bearing resistance from the analytical method was defined as a function of general borehole diameter, expanded borehole diameter, and soil unconfined compressive strength. We also employed the Flac 3D finite difference numerical modeling code to analyze the bearing resistance of the soil conditions. We then created a laboratory experimental model to measure bearing resistance and carried out a pull-out test. The results of these three analyses are presented here, and a regression analysis was performed between bearing resistance and uniaxial compression strength. The laboratory results yield the strongest bearing resistance, with reinforcement 28.5 times greater than the uniaxial compression strength; the analytical and numerical analyses yielded values of 13.3 and 9.9, respectively. This results means that bearing resistance of laboratory test appears to be affected by skin friction resistance. To improve the reliability of these results, a comparison field study is needed to verify which results (analytical, numerical, or laboratory) best represent field observations.
Earthquake Engineering Bedrock Based on the Shear Wave Velocities of Rock Strata in Korea
Sun, Chang-Guk ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 273~281
DOI : 10.9720/kseg.2014.2.273
In most current seismic design codes, design earthquake ground motions are defined by a reference spectrum, based on bedrock and site amplification factors that quantify the geotechnical dynamic conditions. Earthquake engineering bedrock is the fundamental geotechnical formation where the seismic waves are attenuated without amplification. To better define bedrock in an earthquake engineering context, shear wave velocity (
) data obtained from in-situ seismic tests were examined for several rock strata in Korea; these data were categorized by borehole drilling investigations. The
values for most soft rock data in Korea are > 750 m/s, which is the threshold
value for identifying engineering bedrock from a strong motion station. Conversely, VS values are < 750 m/s for 60% of
data in weathered rock in Korea. Thus, the soft (or harder) rock strata below the weathered rock layer in Korea can be regarded as earthquake engineering bedrock.
The Importance of Monitoring Wells Maintenance in Improving Groundwater Quality
Kim, Jeong-Woo ; Seo, Yongkyo ; Kim, Rak-Hyeon ; Cheon, Jeong-Yong ;
The Journal of Engineering Geology, volume 24, issue 2, 2014, Pages 283~295
DOI : 10.9720/kseg.2014.2.283
Groundwater monitoring wells are important to maintain their performance for long term monitoring. The monitoring wells with extensive internal incrustation by clay adsorption were selected for this study. The performance of these monitoring wells was improved by pump washing, tube replacements for dedicated samplers, and well surging. After each improvement, the Mg, Mn, and Zn concentrations were increased. The results show that under these conditions, the monitoring wells must be carefully inspected at least once a year. Even in the case of no abnormal phenomenon like as internal incrustation, the monitoring wells need to be serviced at least once every four to five years to guarantee that they are effectively monitoring groundwater quality.