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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 26, Issue 2 - Jun 2016
Volume 26, Issue 1 - Mar 2016
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Groundwater Ages and Flow Paths at a Coastal Waste Repository Site in Korea, Based on Geochemical Characteristics and Numerical Modeling
Cheong, Jae-Yeol ; Hamm, Se-Yeong ; Koh, Dong-Chan ; Lee, Chung-Mo ; Ryu, Sang Min ; Lee, Soo-Hyoung ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 1~13
DOI : 10.9720/kseg.2016.1.1
Groundwater flow paths and groundwater ages at a radioactive waste repository located in a coastal area of South Korea were evaluated using the hydrochemical and hydrogeological characteristics of groundwater, surface water, rain water, and seawater, as well as by numerical modeling. The average groundwater travel time in the top layer of the model, evaluated by numerical modeling and groundwater age (34 years), approximately corresponds to the groundwater age obtained by chlorofluorocarbon (CFC)-12 analysis (26-34 years). The data suggest that the groundwater in wells in the study area originated up-gradient at distances of 140-230 m. Results of CFC analyses, along with seasonal variations in the δ
O and δD values of groundwater and the relationships between
Rn concentrations and δ
O values and between
Rn concentrations and δD values, indicate that groundwater recharge occurs in the summer rainy season and discharge occurs in the winter dry season. Additionally, a linear relationship between dissolved SiO
concentrations and groundwater ages indicates that natural mineralization is affected by the dilution of groundwater recharge in the rainy summer season.
Using a Borehole Stability Device for Hydraulic Testing in Unconsolidated Alluvium
Won, Kyoung-Sik ; Kim, Chunsoo ; Chae, Soo-Yong ; Shin, Dong-Min ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 15~22
DOI : 10.9720/kseg.2016.1.15
Hydraulic falling head and slug tests were carried out in an alluvium aquifer using a borehole stability device. The hydraulic testing had proved difficult in alluvial formations of sands and gravels due to borehole collapse and unstable borehole walls within the test section. This study aims to improve the hydraulic test results by using a borehole stability device. The device can minimize the collapse of borehole walls, and the use of a filter with a constant opening ratio improves the calculations per unit area of the test section. Permeability obtained from the falling head test without a borehole stability device was 8.82 × 10
m/sec. When the borehole stability device was installed in the same test section the measured permeability increased to 4.00 × 10
m/sec, which is 4.5 times that obtained without the borehole device. The relatively low permeability obtained using the conventional test method is attributed to the presence of a fine-grained slime generated during drilling and a reduction of the test area in the test interval due to a gradual collapse of the borehole walls. This study considers how the use of a borehole stability device to prevent borehole collapse can influence the results of hydraulic tests in alluvial formations. It is expected that the results can be used as a basis for improving the reliability and applicability of hydraulic tests performed in alluvial aquifers.
Landslide Susceptibility Analysis : SVM Application of Spatial Databases Considering Clay Mineral Index Values Extracted from an ASTER Satellite Image
Nam, Koung-Hoon ; Lee, Moung-Jin ; Jeong, Gyo-Cheol ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 23~32
DOI : 10.9720/kseg.2016.1.23
This study evaluates landslide susceptibility using statistical analysis by SVM (support vector machine) and the illite index of clay minerals extracted from ASTER(advanced spaceborne thermal emission and reflection radiometer) imagery which can be use to create mineralogical mapping. Landslide locations in the study area were identified from aerial photographs and field surveys. A GIS spatial database was compiled containing topographic maps (slope, aspect, curvature, distance to stream, and distance to road), maps of soil properties (thickness, material, topography, and drainage), maps of timber properties (diameter, age, and density), and an ASTER satellite imagery (illite index). The landslide susceptibility map was constructed through factor correlation using SVM to analyze the spatial database. Comparison of area under the curve values showed that using the illite index model provided landslide susceptibility maps that were 76.46% accurate, which compared favorably with 74.09% accuracy achieved without them.
Interpretation of Deformation History and Paleostress Based on Fracture Analysis Exposed in a Trench
Gwon, Sehyeon ; Kim, Young-Seog ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 33~49
DOI : 10.9720/kseg.2016.1.33
The study area, located in Sinam-ri, Ulsan, in the southeastern part of the Korean Peninsula, is mainly composed of hornblende granite (ca. 65 Ma). Fracturing and reactivation of a fault striking ENE-WSW was strongly controlled by the intrusion of a mafic dyke (ca. 44 Ma), which behaves as a discontinuity in the mechanically homogeneous pluton, increasing the instability of the basement in this area. A geometric and kinematic study undertaken to interpret the faults and fractures was performed in a trench excavated almost perpendicular to the orientation of the dyke. The analysis of structural elements, such as dykes, veins, and faults, is used to infer the deformation history and to determine the paleostress orientations at the time of formation of the structures. The deformation history established based on this analysis is as follows: (1) NNE-SSW, E-W, ENE-WSW, and NE-SW trending fractures had already developed in the pluton before dyke intrusion; (2) felsic dykes intruded under conditions of σ
oriented N-S and σ
oriented E-W; (3) mafic dykes intruded under conditions of σ
oriented E-W and σ
oriented N-S; (4) dextral reactivation of the main fault associated with the development of hydrothermal quartz veins under conditions of σ
oriented E-W and σ
oriented N-S; (5) sinistral reactivation of the main fault and high-angle normal faults under conditions of σ
oriented NE-SW and σ
oriented NW-SE; and (6) dextral reactivation of the main fault and NE-SW low-angle reverse faults under conditions of σ
oriented NW-SE and σ
oriented NE-SW. These results are consistent with the tectonic history of the Pohang-Ulsan block in the southeastern part of the Korean Peninsula, and indicates the tectonic deformation of the southern area of the Ulsan fault bounded by Yangsan fault was analogous to that of the Pohang-Ulsan area from the Cenozoic. This work greatly aids the selection of sites for critical facilities to prevent potential earthquake hazards in this area.
Field Application of a Precast Concrete-panel Retaining Wall Adhered to In-situ Ground
Min, Kyoung-Nam ; Lee, Jae-Won ; Lee, Jung-Gwan ; Kang, In-Kyu ; Ahn, Tae-Bong ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 51~61
DOI : 10.9720/kseg.2016.1.51
New building methods are needed to aid increased inner-city redevelopment and industrial construction. A particular area of improvement is the efficient use of cut slopes, with the minimization of associated problems. A retaining wall of precast panels can resist the horizontal earth pressure by increasing the shear strength of the ground and reinforcing it through contact with the panels. Precast panels allow quick construction and avoid the problem of concrete deterioration. Other problems to be solved include the digging of borrow pits, the disposal of material cut from the slope, and degradation of the landscape caused by the exposed concrete retaining wall.This study suggest the methods of improvement of an existing precast panel wall system by changing the appearance of the panels to that of natural rock and improving the process of adhering the panel to a vertical slope. The panels were tested in the laboratory and in the field. The laboratory test verified their specific strength and behavior, and the field test assessed the panels' ground adherence at a vertical cutting. Reinforcement of the cutting slope was also measured and compared with the results of 3D numerical analysis. The results of laboratory test, identified that the shear bar increase the punching resistance of panel. And as a results of test construction, identified the construct ability and field applicability of the panel wall system adhered to in-situ ground. In addition to that, extended measurement and numerical analysis, identified the long-term stability of panel wall system adhered to in-situ ground.
Ground Subsidence Caused by the Development of Underground Karstic Networks in Limestone Terrain, Taebag City Korea
Lee, Byung-Joo ; Park, SungWook ; Kim, Dea-Hong ; Song, Young-Karb ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 63~70
DOI : 10.9720/kseg.2016.1.63
The aim of this study is the safety and an accident prevention in limestone terrain by the underground tunneling. The geology of the study area consists of a Paleozoic sedimentary sequence dominated by limestone, sandstone, shale, and carbonaceous shale. The sequence gently dips to the northeast but the joint contains steep with variable trend. A significant fracture zone is developed in the limestone and shale beds, sub-parallel to bedding, and follows in part the limestone-sandstone contact. Monitoring of groundwater levels in the area shows marked fluctuations in the water table, which repeatedly rose to a level of -4 m before sinking to -15 m. These cycles occurred in mid-May, 2007 and in early and middle June. The data indicate that these fluctuations were unrelated to rainfall that occurred during the study period. We infer that the fluctuations were associated with the development of underground karstic networks along the deep fracture zone, and overlying ground subsidence is likely related to the rapid sinking of groundwater and the associated strong downward suction force.
Occurrence of Radionuclides in Groundwater of Korea According to the Geological Condition
Yun, Sang Woong ; Lee, Jin-Yong ; Park, Yu-Chul ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 71~78
DOI : 10.9720/kseg.2016.1.71
This study aimed to evaluate the occurrence of natural radionuclides in Korean groundwater. Groundwater radionuclide data for the period 2000-2011 were obtained from the National Institute of Environmental Research and published literature, classified into five groups according to host rock type, and used to construct detailed concentration maps. Radon, uranium, gross-α, and radium concentrations ranged from 0.4 to 64,688.0 pCi/L (mean: 4,907 pCi/L), 0 to 2,297 μg/L (mean: 27.5 μg/L), 0 to 312 pCi/L (mean: 3.9 pCi/L), and 0 to 17.4 pCi/L (mean: 0.2 pCi/L), respectively. Radon concentrations in 562 of a total 1,501 wells (i.e., 53.5%) exceeded 4,000 pCi/L, which is the acceptable contamination threshold established by the United States Environmental Protection Agency. Uranium, gross-α, and radium concentrations exceeded the respective thresholds of 30 μg/L, 15 pCi/L, and 5 pCi/L in 121 of 1,031 wells (11.9%), 34 of 978 wells (3.5%), and 4 of 89 wells (4.5%), respectively. The mean radionuclide concentration in groundwaters hosted by igneous and metamorphic rocks was higher than that in groundwaters hosted by other rock types, such as volcanics, carbonates, and other sedimentary rocks. The correlations between individual radionuclides were weak or insignificant.
A Study on Corrosion Properties of Reinforced Concrete Structures in Subsurface Environment
Kwon, Ki-jung ; Jung, Haeryong ; Park, Joo-Wan ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 79~85
DOI : 10.9720/kseg.2016.1.79
A concrete silo plays an important role in subsurface low- and intermediate-level waste facilities (LILW) by limiting the release of radionuclides from the silo geosphere. However, due to several physical and chemical processes the performance of the concrete structure decreases over time and consequently the concrete loses its effectiveness as a barrier against groundwater inflow and the release of radionuclides. Although a number of processes are responsible for degradation of the silo concrete, it is determined that the main cause is corrosion of the reinforcing steel. Therefore, the time it takes for the silo concrete to fail is calculated based on two factors: the initiation time of corrosion, defined as the time it takes for chloride ions to penetrate through the concrete cover, and the propagation time of corrosion. This paper aims to estimate the time taken for concrete to fail in a LILW disposal facility. Based on the United States Department of Energy (DOE) approach, which indicates that concrete fails completely once 50% of the volume of the reinforcing steel corrodes, the corrosion propagation time is calculated to be 640 years, which is the time it takes for corrosion to penetrate 0.640 cm into the reinforcing steel. In addition to the corrosion propagation time, a diffusion equation is used to calculate the initiation time of corrosion, yielding a time of 1284 years, which post-dates the closure time of the LILW disposal facility if we also consider the 640 years of corrosion propagation. The electrochemical conditions of the passive rebar surface were modified using an acceleration method. This is a useful approach because it can reduce the test time significantly by accelerating the transport of chlorides. Using instrumental analysis, the physicochemical properties of corrosion products were determined, thereby confirming that corrosion occurred, although we did not observe significant cracks in, or expansion of, the concrete. These results are consistent with those of Smartet al., 2006 who reported that corrosion products are easily compressed, meaning that cracks cannot be discerned by eye. Therefore, it is worth noting that rebar corrosion does not strongly influence the hydraulic conductivity of the concrete.
Numerical Simulation of Groundwater Flow in Feterogenetic Rockmass of Unsaturated Condition
Ha, Jaechul ; Lee, Jeong Hwan ; Cheong, Jae-yeol ; Jung, Haeryong ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 87~99
DOI : 10.9720/kseg.2016.1.87
We present the results of two-dimensional numerical simulations predicting the flow of groundwater in a fractured unsaturated zone. We applied the k-field distribution of permeability derived from discrete fracture network (DFN) modeling as the hydraulic properties of a model domain. To model an unsaturated zone, we set the depth from the ground surface to the underground aquifer. The rate of water infiltration into the unsaturated zone was divided into two parts, an artificial structure surface and unsaturated soil zone. The movement of groundwater through the unsaturated zone was simulated with particular emphasis on contaminant transport. It was clearly observed that the contaminants dissolved in groundwater transported vertically from the ground surface to the saturated zone.
Physical and Mechanical Properties of Cements for Borehole and Stability Analysis of Cement Sheath
Kim, Kideok ; Lee, Hikweon ; Kim, Taehee ; Kim, Gyo-Won ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 101~115
DOI : 10.9720/kseg.2016.1.101
We carried out laboratory material tests on two cements (KS-1 ordinary Portland and Class G) with changing W/S (Water/Solid) and the content of fly ash in order to evaluate their physical and mechanical properties. The specimens of KS-1 ordinary Portland cement were prepared with varying W/S (Solid=cement) in weight, while those of Class G cement were prepared with changing the content of fly ash in volume but maintaining W/S (Solid=cement+fly ash). The results of the material tests show that as the W/S in KS-1 ordinary Portland cement and the content of fly ash in Class G cement increase, the properties (density, sonic wave velocity, elastic constants, compressive and tensile strengths, thermal conductivity) decrease, but porosity and specific heat increase. In addition, an increase in confining pressure and in the content of fly ash leads to plastic failure behavior of the cements. The laboratory data were then used in a stability analysis of cement sheath for which an analytical solution for computing the stress distribution induced around a cased, cemented well was employed. The analysis was carried out with varying the injection well parameters such as thickness of casing and cement, injection pressure, dip and dip direction of injection well, and depth of injection well. The analysis results show that cement sheath is stable in the cases of relatively lower injection pressures and inclined and horizontal wells. However, in the other cases, it is damaged by mainly tensile failure.
Permeability and Strength of Cements Exposed to Supercritical CO
for Varying Periods
Lee, Hikweon ; Kim, Kideok ; Kim, Taehee ; Kim, Gyo-Won ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 117~128
DOI : 10.9720/kseg.2016.1.117
Chemical reaction tests were performed to assess the properties of hardened specimens of cement pastes (KS-1 Portland and Class G) exposed to supercritical CO
for 1, 10, and 100 days. After exposure, the samples' measured permeability and strength were compared with values measured for pristine samples. The pristine cements had permeabilities of 0.009~0.025 mD, which increased by one order of magnitude after 100 days of exposure (to 0.11~0.29 mD). The enhancement of permeability is attributed to the stress release experienced by the samples after removal from the pressure vessel after exposure. Despite its enhancement, the measured permeability mostly remained lower than the API (American Petroleum Institute) recommended maximum value of 0.2 mD. The degradation of the cement samples due to exposure to supercritical CO
led to a layer of altered material advancing inwards from the sample edges. The Vickers hardness in the altered zone was much higher than that in the unaltered zone, possibly owing to the increase in density and the decrease in porosity due to the carbonation that occurred in the altered zone. Hardness close to the edge within the altered zone was found to have decreased significantly, which is attributed to the conversion of C-S-H into less-strong amorphous silica.
Maintenance of Hazardous Steep Slopes on National Park Trails
Kim, Hong Gyun ; Kim, Tae Ho ; Kim, Jae Hak ; Kwak, Jae Hwan ; Park, Sung Wook ; Choi, Soo Won ; Song, Young Karb ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 129~142
DOI : 10.9720/kseg.2016.1.129
National parks, which are located mainly in mountainous areas, are always at risk of damage by landslides. The goal of this study is to establish a method for systematically maintaining hazardous steep slopes along trails in national parks. We produced a checklist suitable for each of the 19 national parks nationwide and investigated 183 slopes. The aim of these investigations is to recommend appropriate slope-stability countermeasures, including field investigations and stability analysis. We made preliminary investigations at specific sites, evaluating the slope hazard using specialized equipment such as terrestrial LiDAR. An investment priority formula was developed, and ranking and hazardous grades were calculated as part of a long-term maintenance plan. Finally, to systematically manage dangerous slopes and to house all the field data within one system, we developed the "Slope Maintenance System in National Parks" based on web server that can show various information for slopes.
Estimating Soil Thickness in a Debris Flow using Elastic Wave Velocity
Min, Dae-Hong ; Park, Chung-Hwa ; Lee, Jong-Sub ; Yoon, Hyung-Koo ;
The Journal of Engineering Geology, volume 26, issue 1, 2016, Pages 143~152
DOI : 10.9720/kseg.2016.1.143
To estimate the stability of a debris flow it is necessary to know the mass of surface soil, cohesion, slope, and friction angle. Given that the mass of surface soil is a function of soil thickness and mass density, it is important to obtain reliable estimates of soil thickness across a wide area. The objective of this paper is to estimate soil thickness using the elastic wave velocity with a new standard velocity. Tests are performed in debris-flow hazard areas, after which four profiles are selected to obtain the elastic wave velocity. Dynamic cone penetration tests are carried out to find the soil thickness at 18 points. The elastic wave velocity shows the area consists of 3~4 layers, and soil thicknesses are predicted by utilizing the new standard. The elastic wave velocity and dynamic cone penetration tests yield large differences in soil thickness. Therefore, this study shows that the new standard is useful not only in estimating soil thickness but also in improving the reliability of estimates of soil thickness.