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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 25, Issue 4 - Dec 2015
Volume 25, Issue 3 - Sep 2015
Volume 25, Issue 2 - Jun 2015
Volume 25, Issue 1 - Mar 2015
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CLSM [Confocal Laser Scanning Microscope] Observation of the Surface Roughness of Pressurized Rock Samples During Freeze/Thaw Cycling
Kim, Hye-jin ; Choi, Junghae ; Chae, Byung-gon ; Kim, Gyo-won ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 165~178
DOI : 10.9720/kseg.2015.2.165
Physical and chemical weathering degrades rock, affecting its structural properties and thus the stability of stone buildings or other structures. Confocal laser scan microscopy (CLSM) is used here to observe temporal changes in the surface roughness of rock samples under simulated accelerated weathering. Samples were pressurized to 50, 55, or 70 MPa using a pressure frame, and subjected to freeze/thaw cycling controlled by a thermostat. The temperature was cycled from -20℃ to 40℃ and back. After each 20 cycles, CLSM was used to assess the change in surface roughness, and roughness factors were calculated to quantify the progression of the surface condition over time. Variations in cross-section line-roughness parameters and surface-roughness parameters were analyzed for specific parts of the sample surfaces at 5× and 50× magnification. The result reveals that the highest and lowest values of the roughness factors are changed according to elapsed time. Freezing/thawing at high pressure caused larger changes in the roughness factor than at low pressure.
A Study of the Compaction Effect of Expansive Admixture for the Development of an Expansive Compaction Packer
Kim, Jin-Chun ; Park, Ki-Yeon ; Lee, Dong-Ik ; Lee, Gyu-Sang ; Kim, Sang-Gyun ; Yoo, Byung-Sun ; Choi, Gi-Sung ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 179~188
DOI : 10.9720/kseg.2015.2.179
Although permeating injection is ideal for grouting reservoir embankments, it is usually combined with fracturing injection for grouting, which can disturb the original soil. Compaction with low expansive pressure followed by grout injection can overcome this problem. An expansive compaction (EC) packer was developed in this work to easily apply sequential injection and compaction at a work site. Furthermore, to achieve compaction around the grouting hole, a mixture of expansive admixtures and grout was injected with the EC packer to trigger an increase in volume of the grout material. This work verifies the compaction effect of the EC packer and the expansive admixture. It reports the concepts of the EC packer, the range of expansive compaction, the effectiveness of injection, and the results of indoor tests performed to verify the effectiveness of the expansive admixtures. The indoor testing comprised a preparatory test and the main test. The preparatory test assessed the admixtures for their compaction effects, while the main test measured and analyzed the admixtures' expansive force, pressure, and compaction effect with a mold to verify the effectiveness of the compaction effect.
Slopes Risk Assessment Techniques through Pattern Classification
Kim, Min-Seub ; Kim, Jin-Young ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 189~199
DOI : 10.9720/kseg.2015.2.189
Our country's leading granite weathered soil of the ground slope failures that occur in cutting slope most cases, it does not require in-depth to the shear strength most of the surface layer is affected by weathering (1~2 m) at a shallow depth close to the ground, it is important to identify the reliability. Based on the result obtained in actual field investigation, the field slope type was classified by each type of wedge slope, Infinite slope, finite slope -I and finite slope -II, and the slope stability was examined respectively. In addition, using the numerical analysis results, the relationship between the slope inclination angle and safety factor was analyzed and it tried to offer basic data to which the stability in the field slope was able to be estimated by analyzing the safety factor change of the slope according to the slope type. In this study, classified into four types of natural slope, safety factor estimation method by slope types is proposed through the numerical analysis. However, some limit exists in generalizing in this research because it does not test various case studies. Therefore, the case study of a wide range of various sypes to assess the safety of various types slope can be made, accommodate a wide range of field conditions reasonable risk evaluation criteria may be derived.
Assessment of Surface Topographic Effect in Earthquake Ground Motion on the Upper Slope via Two-Dimensional Geotechnical Finite Element Modeling
Sun, Chang-Guk ; Bang, Kiho ; Cho, Wanjei ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 201~213
DOI : 10.9720/kseg.2015.2.201
Site effects resulting in the amplification of earthquake ground motion are strongly influenced not only by the subsurface soil conditions and structure, but also by the surface topography. Yet, over the last several decades, most studies of site-specific seismic responses in Korea have focused primarily on the seismic amplification associated with geologic and soil conditions. For example, the effects of local geology are now well established and have been incorporated into current Korean seismic design codes, whereas topographic effects have not been considered. To help address this shortcoming, two-dimensional (2D) seismic site response analyses, using finite element (FE) ground modeling with three different slope angles, were performed in order to assess the site effects of surface topography. We then compared our results, specifically peak ground acceleration (PGA) and acceleration response spectrum, to those of one-dimensional (1D) FE model analyses conducted alongside our study. Throughout much of the upper slope region, PGAs and spectral accelerations are larger in the 2D analyses than in the 1D analyses as a result of the topographic effect.
Replacement of Saline Water through Injecting Fresh Water into a Confined Saline Aquifer at the Nakdong River Delta Area
Won, Kyung-Sik ; Chung, Sang Yong ; Lee, Chang-Sup ; Jeong, Jae-Hoon ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 215~225
DOI : 10.9720/kseg.2015.2.215
We performed injection tests in a deep-seated confined aquifer to assess the potential of artificial recharge as a means of preventing saltwater contamination, thereby securing groundwater resources for the Nakdong Delta area of Busan City, Korea. The study area comprises a confined aquifer, in which a 10-21-m-thick clay layer overlies 31.5-36.5 m of sand and a 2.8-11-m-thick layer of gravel. EC logging of five monitoring wells yielded a value of 7-44 mS/cm, with the transition between saline and fresh water occurring at a depth of 15-38 m. Above 5 m depth, water temperature is 10-15.5℃, whereas between 5 and 50 m depth the temperature is 15.5-17℃. Approximately 950 m
of fresh water was injected into the OW-5 injection well at a rate of 370 m
/day for 62 hours, after which the fresh water zone was detected by a CTD Diver installed at a depth of 40 m. The persistence of the fresh water zone was determined via EC and temperature logging at 24 hours after injection, and again 21 days after injection. We observed a second fresh water zone in the OW-2 well, where the first injection test was performed more than 20 days before the second injection test. The contact between fresh and saline water in the injection well is represented by a sharp boundary rather than a transitional boundary. We conclude that the injected fresh water occupied a specific space and served to maintain the original water quality throughout the observation period. Moreover, we suggest that artificial recharge via long-term injection could help secure a new alternative water resource in this saline coastal aquifer.
A Terrestrial LiDAR Based Method for Detecting Structural Deterioration, and Its Application to Tunnel Maintenance
Bae, Sang Woo ; Kwak, Jae Hwan ; Kim, Tae Ho ; Park, Sung Wook ; Lee, Jin Duk ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 227~235
DOI : 10.9720/kseg.2015.2.227
In recent years, owing to the frequent occurrence of natural disasters, the inspection and maintenance of structures have become increasingly important on a national scale. However, because most structural inspections are carried out manually, and due to the lack of objectivity in data acquisition, quantitative data are not always available. As a result, researchers are seeking ways to collect and standardize survey data using terrestrial laser scanning, thereby bypassing the limitations associated with visual investigations. However, field data acquired using a laser scanner have been required to measure changes in structure geometry resulting from passive deterioration. In this study, we demonstrate that it is possible to identify the processes of structural deterioration (e.g., efflorescence, leakage, delamination) using intensity data from terrestrial laser scanning. Additionally, we confirm the viability of automated classification of alteration type and objectification of the polygon area by establishing intensity characteristics. Finally, we show that our method is effective for structural inspection and maintenance.
A Study on Dynamic Analyses of Cut and Cover Tunnel during Earthquakes
Park, Sung-Sik ; Moon, Hong-Duk ; Park, Si-Hyun ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 237~250
DOI : 10.9720/kseg.2015.2.237
Underground structures such as a tunnel have been considered as safer than structures on the ground during earthquake. However, severe damages of underground structures occurred at subway tunnel during 1995 Kobe Earthquake and such damages are gradually increased. In this study, a dynamic behavior of a cut and cover tunnel surrounded by weathered soils is investigated using Mohr-Coulomb Model. Parametric study was carried out for boundary conditions, tensile strength, and earthquake magnitudes. The results of numerical analyses in terms of ground deformations and stresses acting on the lining were quite dependent on the side boundary condition (free or fix conditions) and tensile strength of surrounding soils. The ground was deformed upward at the end of earthquake when the side boundary condition was fixed, whereas residual deformations were not predicted when it was free. When the tensile strength of a soil was set to the same as its cohesion, residual deformation was less than 1cm, regardless of side boundary conditions or input accelerations. In addition to that, stress conditions at the maximum deformation and end of earthquake were within an allowable range and considered as safe. Proper boundary conditions and material properties such as tensile strength are quite important because they may significantly impact on the results of dynamic analyses.
Analysis of Scale and Shape of Limestone Cavities using Borehole Drilling and Geophysical Investigations
Song, Gyu-Jin ; Yun, Hyun-Seok ; Jang, Il-Ho ; Choi, Yong-Seok ; Seo, Yong-Seok ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 251~263
DOI : 10.9720/kseg.2015.2.251
Geological mapping, borehole drilling, electrical resistivity, and seismic tomography surveys were conducted in order to map underground cavities and better understand the mechanisms driving subsidence in a limestone region in Korea. Limestone outcrops in the study area generally alternate between calcite-rich and calcite-poor rock. The results reveal that in areas experiencing subsidence, cavities occur mainly around soil-rock boundaries at depths of 7~14 m. These results are based on comparative analyses of electrical resistivity, seismic tomography, and borehole logging data. The volumes of the cavities are relatively small in a range of 558~835 ㎥ and they have a shape typical of suffosion sinkholes, which are typically found where sandy soils overlie bedrock cavities.
Determination of Earthquake Loads and Finite Element Analysis of Circular Water Reservoirs with a Large Size over 5,000 ton
Lee, Sang-Youl ; Jeong, Gyo-Cheol ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 265~272
DOI : 10.9720/kseg.2015.2.265
Finite element analyses were performed on large-sized (>5000 ton) stainless steel circular water reservoirs subjected to earthquake loading for different stainless steel materials. The earthquake load inputs for the analyses were selected by the guidelines in the Korean Standards Association specification KS B 6283. Seismic effects can be heavily dependent on water capacity, especially for large reservoirs. The numerical results show the interactions between the different load combinations and other parameters such as the water capacity and stainless steel materials. Structural performance is also evaluated for the various load combinations.
Estimation of Drilling Velocity for Horizontal Wells Based on Alluvial Sediment Characteristics
Kim, Gyoo-Bum ; Lee, Jeong-Woon ; Lee, Chi-Hyung ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 273~280
DOI : 10.9720/kseg.2015.2.273
Delays in horizontal well drilling when encountering heterogeneous sediments can have negative effects on the construction process at a riverbank filtration site. Grain size analysis, including calculation of the coefficient of uniformity and the coefficient of curvature, was conducted on soil samples collected at each drilling depth during the process of drilling horizontal wells. These results were then used to develop a linear equation for estimating drilling velocity using the coefficient of uniformity and the coefficient of curvature as inputs. Testing of the linear equation in other horizontal wells indicates that the equation is most appropriate for coarse-sand-sized and well-sorted sediment. Because this study was conducted in a region with small- to medium-sized streams, more data are needed from larger rivers to modify the general equation. Our results will provide better estimates of drilling velocity, in turn enabling more detailed design and more effective construction management at riverbank filtration sites.
Frequency Distribution Characteristics of Formation Density Derived from Log and Core Data throughout the Southern Korean Peninsula
Kim, Yeonghwa ; Kim, Ki Hwan ; Kim, Jongman ; Hwang, Se Ho ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 281~290
DOI : 10.9720/kseg.2015.2.281
Log density data were collected and compared with the core density data throughout the southern Korean Peninsula. The comparison reveals that the log densities obtained from gamma-gamma log are much lower than the core densities obtained from laboratory density measurement of core samples. The anomalously low log densities can be attributed to the small-source density log data. Correlation analysis reveals differences between densities derived from the two methods, indicating that a data quality problem arises when using small-source log data. The problem is probably due to the fact that small-source data have not been obtained under ideal conditions for maintaining the appropriate relationship between gamma response and formation density. The frequency distribution characteristics of formation density in the southern Korean Peninsula could be determined using the core and the standard-source log data which are well-correlated.
Characteristics of Hydraulic Head Variation at Multi-packer Wells in a Coastal Area
Cheong, Jae-Yeol ; Hamm, Se-Yeong ; Ok, Soon-Il ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 291~298
DOI : 10.9720/kseg.2015.2.291
For hydrogeological studies, it is of importance to observe hydraulic head in order to interpret groundwater flow, characterize aquifers, and calibrate groundwater flow model. This study analyzed the zonal variation of hydraulic heads at the eight monitoring wells (GM-1~GM-8) installed with multi-packers in a coastal area and verified vertical and lateral trends of the hydraulic gradients. Hydraulic heads were expressed as the depth of water because the monitoring wells have different depths. The hydraulic gradient at the nearest well (GM-5) shows 0.0142 with increasing trend of hydraulic gradient along depth. This fact indicates typical phenomenon of the discharge area. On the other hand, GM-1 and GM-2 wells in coastal area demonstrate constant hydraulic gradient down to the depth of 100 meters while at the zone of deeper than 100 m the hydraulic gradients illustrate 0.0196 and 0.0735, respectively. This indicates that horizontal flow is dominant at shallower zone than 100 m whereas upward flow is dominant at the zone deeper than 100 m. GM-3 well located farther than the other wells from the coast shows a small hydraulic gradient of 0.0046 that evidences a prevalent horizontal flow between the recharge area and the discharge area.
Analysis on Failure Critical Depth of Unsaturated Landslide Zone According to the Geological Condition
Nam, Koung-Hoon ; Kim, Min-Gyu ; Jeong, Gyo-Cheol ;
The Journal of Engineering Geology, volume 25, issue 2, 2015, Pages 299~304
DOI : 10.9720/kseg.2015.2.299
Slope stability analysis of unsaturated soil slopes due to rainfall infiltration is an important issue in evaluating landslide analysis and stability assessment. The purpose of this study is to establish the critical depth considering weathered soil of parent rock and rainfall intensity at main scarp in national landslide. Based on the analytical results, it is found that as rainfall duration and Slope angle increased, the critical depth of gneiss-weathered soil increased from 3.00 m to 3.77 m, the critical depth of granite weathered-soil increased from 1.75 m to 2.40 m, and the critical depth of mudstone-weathered soil increased from 3.00 m to 4.15 m, respectively. The critical depth of granite-weathered soil with low cohesion and high internal friction angle is much lower than those of other soils. It is interestingly shown that a decrease in the safety factor is highly significant, much affected by the slope increase rather than the rainfall intensity.