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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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Numerical Study of Unsaturated Infinite Slope Stability regarding Suction Stress under Rainfall-induced Infiltration Conditions
Song, Young-Suk ; Hwang, Woong-Ki ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 1~8
DOI : 10.9720/kseg.2014.1.1
Numerical stability analysis of an unsaturated infinite slope under rainfall-induced infiltration conditions was performed using generalized effective stress to unify both saturated and unsaturated conditions The soil-water characteristic curve (SWCC) of sand with a relative density of 75% was initially measured for both drying and wetting processes. The hydraulic conductivity function (HCF) and suction stress characteristic curve (SSCC) were subsequently estimated. Under the rainfall-induced infiltration conditions, transient seepage analysis of an unsaturated infinite slope was performed using the finite element analysis program, SEEP/W. Based on these results, the stability of an unsaturated infinite slope under rainfall-induced infiltration conditions was examined in relation to suction stress. According to the results, the negative pore-water pressure and water content within the slope soil changed over time due to the infiltration. In addition, the variation of the negative pore-water pressure and water content led to a variation in suction stress and a subsequent change in the slope's factor of safety during the rainfall period.
Seismic Stratigraphy and Sedimentary Environment of the Dukjuk-Do Sand Ridge in Western Gyeonggi Bay, Korea
Lee, Yoon-Oh ; Choi, Sang-Il ; Jeong, Gyo-Cheol ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 9~21
DOI : 10.9720/kseg.2014.1.9
We examined high-resolution seismic data, side scan sonar data, surface sediments, and vibrocore samples from a sand ridge off the western part of Dukjuk-Do in Gyeonggi Bay, with the aim of interpretation of seismic stratigraphy and sedimentary environment. Based on the seismic data, the deposited sands are divided into three sedimentary units. 14C age data indicate that the top sequence (sequence I) formed at 5000-6000 yr BP, when a transgression resulted in strong shifting tides. Analyses of the vibrocore samples indicate that sequence II is a paleo-mudflat layer of intertidal sediments dominated by mud. Sequence III consists of terrestrial sediments that are presumed to have been deposited at the end of the Pleistocene, unconformably overlying the acoustic bedrock and Mesozoic granite. The side scan sonar data indicate that sand waves were formed on the seabed on top of the sand ridge. Generally, this is the direction of
, which coincides with the direction of tidal flow. Sand ripples occur away from the top of the sand ridge and are distributed homogeneously across a sandy slope. Vibrocore analyses indicate that the surface sediments and core sediments (samples VC-1, -2, and -3) are homogeneous, without any internal structures, and are characterized by a mixture of medium and fine sand (1-
Characteristics of the Stress Path of a Sabkha Layer Consisting of Carbonate Sand, as Obtained by the Triaxial Test after Particle Crushing
Kim, Seok-Ju ; Yi, Chang-Tok ; Jang, Jae-Ho ; Han, Heui-Soo ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 23~38
DOI : 10.9720/kseg.2014.1.23
The composition of carbonate sands from a sabkha at Ruwais in the UAE differs from that of silica sand, and these sands are crushed easily under low compression pressures. Accordingly, particle crushing of carbonate sand occurs under high pressure, which results in additional settlement and reduces the shear strength. In this study, consolidation and triaxial tests were conducted to analyze the characteristics of carbonate sands following particle crushing. The unusual shear strength graphs of the carbonate sands result from the degree of particle pre-crushing. For the range at p' > p in the p (p')-q diagram, negative (-) excess porewater pressures occur if the axial pressure causes particle crushing that induces exposure of the inner voids. In addition, the q value decreased after particle crushing. In conclusion, the unusual characteristics of the carbonate sands were induced by particle crushing. The triaxial tests revealed that the degree of particle pre-crushing influenced the excess porewater pressure.
Weighted Analysis Method for Estimating the Orientation of Limestone Caves in Korea
Lee, Sang-Kyun ; Park, Hyeong-Dong ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 39~52
DOI : 10.9720/kseg.2014.1.39
Limestone caves that consist of main passages and branches are formed by a variety of processes, and have the characteristic of developing with a preferred orientation controlled by discontinuities such as bedding, joints, and faults around the cave. However, it is difficult to analyze a representative orientation from various orientations. To interpret the overall development orientation of limestone caves, this study proposes new development orientation analysis methods, termed the Average Span Ratio Method (ASRM) and the Individual Development Ratio Method (IDRM), using the weighting of persistence. Nine limestone caves in Korea were randomly selected for testing the new methods. The methods show a stronger development orientation for limestone caves than that obtained by traditional methods, which consider only the distribution of development orientations. Based on an analysis of the relationship between the average span and the dip angle of bedding, it is confirmed that shallowly dipping bedding is a major contributor to the expansion of span in limestone caves. In addition, using scan-line survey data acquired in the field, we perform an RMR analysis of stability of the ground around limestone caves.
Sensitivity Analysis of Model Parameters used in a Coupled Dam-Break/FLO-2D Model to Simulate Flood Inundation
Lee, Khil-Ha ; Son, Myung-Ho ; Kim, Sung-Wook ; Yu, Soonyoung ; Cho, Jin-Woo ; Kim, Jin-Man ; Jung, Jung-Kyu ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 53~67
DOI : 10.9720/kseg.2014.1.53
Numerical modeling is commonly used to reproduce the physical phenomena of dam-break and to compile resulting flood hazard maps. The accuracy of a dam-break model depends on the physical structure that describes the volume of storage, breach formation and progress, input variables, and model parameters. Model input and parameters are subjective in that they are prescribed; hence, caution is needed when interpreting the results. This study focuses on three parameters (breach degree
, shape factor P, and collapse rate k) used when the dam-break model is coupled with FLO-2D (a two-dimensional flood simulation model) to estimate flood coverage and depth etc. The results show that the simulation is sensitive to the shape factor P and the collapse rate k but not to the breach degree
. This study will contribute to reducing flood damage from dam-break disasters in the future.
Effect of Rainfall Intensity, Soil Slope and Geology on Soil Erosion
Nam, Koung-Hoon ; Lee, Dal-Heui ; Chung, Sung-Rae ; Jeong, Gyo-Cheol ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 69~79
DOI : 10.9720/kseg.2014.1.69
This study aims to elucidate the relative importance of geological characteristics, soil slope, and rainfall intensity in relation to soil erosion. To this end, indoor rainfall simulation experiments were carried out under different conditions of rainfall intensities, soil slope, and geological characteristics. The test results show that the factors affect soil erosion in the order of soil slope > rainfall intensity > organic content in the soil. Erosion rates were proportional to rainfall, and increase with increasing clay content. Therefore, the soil erosion rate increases strongly with increasing organic content and clay content. The results show that the soil erosion rate in areas of metamorphic rocks shows a marked increase compared with areas of steep slope and sedimentary rocks. These results indicate that the geological characteristics to produce soil are closely related to sedimentation before and after erosion, providing basic information for the development of models to predict soil erosion rates.
Case Studies for the Stress Measurements on the Shotcrete Tunnel Lining
Kim, Hak Joon ; Kim, Mi-Ran ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 81~89
DOI : 10.9720/kseg.2014.1.81
Stress measurements of shotcrete lining were performed to evaluate the stability of the primary lining and to determine the thickness and the construction timing of the secondary lining. The current situation of stress measurements of shotcrete and problems related to judging the safety of shotcrete linings are presented, based on the results of several case studies. An improved method of performing stress measurements on shotcrete lining is also presented. In evaluating the safety of shotcrete lining, the use of absolute values of measured stresses would improve the reliability of the measurements.
Analysis of Flow Duration and Estimation of Increased Groundwater Quantity Due to Groundwater Dam Construction
Kim, Jong-Tae ; Kim, Gyoo-Bum ; Chung, Il-Moon ; Jeong, Gyo-Cheol ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 91~98
DOI : 10.9720/kseg.2014.1.91
This paper aims to calculate the increase in groundwater quantity following groundwater dam construction, and to assess its impact on surface water. In the study area of Osib-cheon, Yeongdeok, we estimated groundwater quantity, groundwater level, and effective porosity, and examined surface water fluctuations with respect to the increased groundwater quantity based on the flow duration. The results reveal that the increased groundwater quantity was at most
in the total drainage basin of the groundwater dam, and the reduced groundwater quantity was at most
in the lower zone of the groundwater dam. Therefore, the total groundwater resources secured was
and the decrease in groundwater quantity was just 12.27% of the amount of increase. There were changes in discharge rate by up to
, as deduced from an analysis offlow duration as a result of groundwater dam construction. The overall difference between before and after construction of the dam was almost insignificant compared with the previous dam. The present results indicate that dammed groundwater can serve as an alternative water resource with sufficient quantity.
Correlation Between the Point-Load Strength and the Uniaxial Compressive Strength of Korean Granites
Woo, Ik ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 101~110
DOI : 10.9720/kseg.2014.1.101
This study presents the results of a regression analysis of the point-load strength (
) and the uniaxial compressive strength (UCS) of granites in Korea. The regression was carried out for three cases using the least-squares method, reclassifying the granite samples based on their physical properties. The first regression analysis through the origin according to the weathering grade did not give a result with a sufficient degree of confidence, due to the small number of samples. However, the general trend of the correlation between UCS and
according to weathering grade shows that the slope of the linear regression for weathered granite is steeper than that for fresh granite. The second analysis was a simple linear regression for all the granite samples using the least-squares method as well as a linear regression using the bootstrap resampling method in order to increase the confidence level and the accuracy of the regression results. The third regression considered the average strength of granite groups reclassified according to physical properties. These linear regression analyses yielded linear regression equations with slopes of 14 and small standard deviations being similar to values reported in previous studies on Korean granites, but whose intercept values range from 16 to 43 and have a larger standard deviation than those of the present study. In conclusion, it would be advisable to estimate UCS from
, considering the error range derived from the deviation of the regression equations.
Characteristics of Shear Strength and Elastic Waves in Artificially Frozen Specimens using Triaxial Compression Tests
Kim, JongChan ; Lee, Jong-Sub ; Hong, Seung-Seo ; Lee, Changho ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 111~122
DOI : 10.9720/kseg.2014.1.111
For accurate laboratory evaluations of soil deposits, it is essential that the samples are undisturbed. An artificial ground-freezing system is the one of the most effective methods for obtaining undisturbed samples from sand deposits. The objective of this study is to estimate the shear strengths and the characteristics of elastic waves of frozen-thawed and unfrozen specimens through the undrained triaxial compression test. For the experiments, Jumunjin standard sands are used to prepare frozen and unfrozen specimens with similar relative densities (60% and 80%). The water pluviation method is used to simulate the fully saturated condition under the groundwater table. When thawing the frozen specimens, the temperature is measured every minute. After the specimens are completely thawed, undrained triaxial compression tests are conducted using the same procedures as for the unfrozen specimens. During the triaxial tests (saturation, consolidation, and shear phase), compressional and shear waves are measured. The results show that the freeze-thaw process has minor effects on the peak deviatoric stress and shear strength values, and that the process does not affect the internal friction angle. The compressional wave velocity increases with increasing B-value to 1800 m/s in the saturation phase, but tends to remain constant in the process of consolidation and shearing. The shear wave velocity decreases with increasing B-value in the process of saturation, but changes velocity in accordance with the change in effective stress in the processes of consolidation and shearing. The compressional wave velocity has similar values regardless of the freeze-thaw process, but values of shear wave velocity are slighly lower in frozen-thawed specimens than in unfrozen specimens. This study is a preliminary experiment for estimating the shear strength and characteristics of elastic wave velocity in undisturbed frozen specimens that have been obtained using the artificial ground-freezing method.
Basic Concepts and Geological Applications of LiDAR
Kim, Hyun-Tae ; Kim, Young-Seog ; We, Kwang-Jae ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 123~135
DOI : 10.9720/kseg.2014.1.123
Earthquakes can cause serious loss of life and significant property damage. Thus, the study of active faults is important in evaluating future fault activity and hazards caused by future earthquake events. Structural mapping and the tracing of active faults are the primary steps in studies of active faults. Until now, active faults in South Korea have been mapped using aerial photography, satellite images, and low-quality DEMs. Lineament analysis as a means of identifying active faults is relatively difficult in Korea due to geological characteristics (weak tectonic activity) and dense vegetation cover. In this paper, we introduce the basic concept of the LiDAR technique (a new prospective remote sensing method) and a data analysis method that can overcome these problems. This paper will contribute to a better understanding of the airborne LiDAR technique and its application to South Korea. Some preliminary results from Korean and USA LiDAR data show the usefulness of this technique for tracing lineaments, active faults, and terraces in South Korea.
An Example of Changed Design through the Face Mapping and Slope Analysis
Lee, Byung-Joo ; Chae, Byung-Gon ; Lee, Kyoung-Mi ;
The Journal of Engineering Geology, volume 24, issue 1, 2014, Pages 137~146
DOI : 10.9720/kseg.2014.1.137
The geology of the study area which is located in Samkoe-dong, Dong-gu, Daejeon city comprises black slate, limestone, and pebble-bearing phyllitic rock as meta-sedimentary rocks; and biotite granite and quartz porphyry intrusions. Face mapping revealed sliding in three or four sites of contained coaly slate, where the dip of the foliation and other discontinuities is parallel to the surface slope. The cause of the slope sliding is this parallelism as well as the swelling of the coaly slate when wet. In contrast, the slop on the opposite side of the road is relatively stable because the dip of the foliation and other discontinuities are oblique or normal to the surface slope. To ensure slope stability, a cut-and-cover tunnel was designed and constructed for the new road.