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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 22, Issue 4 - Dec 2012
Volume 22, Issue 3 - Sep 2012
Volume 22, Issue 2 - Jun 2012
Volume 22, Issue 1 - Mar 2012
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Experimental Study on the Hysteresis of Suction Stress in Unsaturated Sand
Song, Young-Suk ; Choi, Jin-Su ; Kim, Gyo-Won ;
The Journal of Engineering Geology, volume 22, issue 2, 2012, Pages 145~155
DOI : 10.9720/kseg.2012.22.2.145
The matric suction and volumetric water content of Jumunin standard sand with a relative density of 60% were measured using an Automated Soil-Water Characteristic Curve (SWCC) apparatus during both drying and wetting processes. The test time for the drying process was longer than that for the wetting process, because the flow of water is likely to be protected by air trapped in voids within the soils during the drying process. Based on the matric suction and volumetric water content, the SWCC was estimated using the model proposed by van Genuchten (1980). For the drying process, the unsaturated fitting parameters
, n, and m were 0.399, 8.586, and 0.884, respectively; for the wetting process, the values were 0.548, 5.625, and 8.220, respectively. The hysteresis phenomenon occurred in the SWCCs, which means the SWCC of the drying process is not matched with the SWCC of the wetting process. Using these unsaturated parameters, we estimated the Suction Stress Characteristic Curve (SSCC), based on the relationship between suction stress and the effective degree of saturation. The suction stress showed a rapid decrease when the matric suction exceeds the Air Entry Value (AEV). Therefore, the effective stress of unsaturated soils is different from that of saturated soils when the matric suction exceeds the AEV. The suction stress of the drying process exceeds that of the wetting process for a given effective degree of saturation. The hysteresis phenomenon was also recognized in SSCCs. The hysteresis phenomenon of SSCCs arises from that of SWCCs, which is induced by the ink bottle effect and the contact angle effect. In the case of a sandy slope, the suction stress is positive and acts to enhance the slope stability as the water infiltrates the ground, but is negative when the suction stress exceeds the AEV. The results obtained for the wetting process should be applied in analyses of slope stability, because the process of water infiltration into ground is similar to the wetting process.
Optimal Measurement System for Weak Rock Slopes in an Open-Pit Mine
SunWoo, Choon ; Ryu, Dong-Woo ; Jung, Yong-Bok ; Park, Do-Hyun ;
The Journal of Engineering Geology, volume 22, issue 2, 2012, Pages 157~171
DOI : 10.9720/kseg.2012.22.2.157
The slope design of an open-pit mine must ensure slope stability and economic feasibility. The overall slope angle of the pit is therefore the main factor of concern because of limited support or reinforcement options available in such a setting. This study examines the optimal measurement system for monitoring the behavior of the slope in an open-pit mine using displacement measurement, data analysis, and numerical simulations for a coal mine at Pasir, Indonesia. The area of slope to be managed is extensive and the maximum displacement, as calculated by numerical analysis, is about 3,000 mm. The displacement data, measured by inclinometer and GPS, were analyzed, and the applicability of SSR (slope stability radar) was reviewed in comparison with other monitoring systems.
Experimental Study on the Deformation and Failure Behavior of Tono Granite
Choi, Jung-Hae ; Chae, Byung-Gon ;
The Journal of Engineering Geology, volume 22, issue 2, 2012, Pages 173~183
DOI : 10.9720/kseg.2012.22.2.173
The nature of surface deformation of Tono granite was investigated using a confocal laser scanning microscope (CLSM) under water-saturated stress relaxation conditions. A new apparatus was developed for this experiment, enabling continuous measurements of stress-strain and simultaneous observations of surface deformation by CLSM. The amounts of grain contact deformation and intra-granular surface deformation were calculated using a finite element method. The results reveal that intense grain contact deformation and intra-granular surface deformation occurred during the period of stress relaxation, and that the intensity of this deformation increased with increasing applied stress. Finite element method (FEM) results show that the strain of grain boundary was greater than strain of inter-granular surface. Contour maps of these local strains were compiled for individual grains and their boundaries, revealing intense deformation at the boundaries between biotite and quartz under compressional stress. This result was a consequence of the mechano-chemical effect of biotite and quartz minerals. Biotite in granite has a layered structure of iron-magnesium-aluminum silicate sheets that are weakly bonded together by layers of potassium ions. In contrast, quartz occurs as stable spherical grains.
Development of a Mobile System for Investigating and Maintaining Steep Slopes
Song, Young-Karb ; Kim, Tai-Hoon ; Oh, Jeong-Rim ; Son, Young-Jin ;
The Journal of Engineering Geology, volume 22, issue 2, 2012, Pages 185~194
DOI : 10.9720/kseg.2012.22.2.185
The efficient maintenance and management of steep slopes often require excessive professional resources and quantitative investigations. Therefore, it is important to develop technology for objective scientific site investigations and quantitative evaluations of steep slopes. This study proposes a 'Mobile System' for steep slopes in order to improve the effectiveness of site investigations compared with conventional methods using anevaluati on table. By analyzing site investigations and desktop studies, the required software and hardware are identified to develop the 'Mobile System', consisting of a 'Field Information Input System' and an 'Analysis System'. The applicability of the system is verified by its application to an area with steep slopes affected by debris flows. The use of this system is expected to increase the efficiency of maintaining steep slope sand to reduce the time and resources required.
Hydrogeological Characteristics of the Wangjeon-ri PCWC area, Nonsan-city, with an Emphasis on Water Level Variations
Cho, Byong-Wook ; Yun, Uk ; Lee, Byeong-Dae ; Ko, Kyung-Seok ;
The Journal of Engineering Geology, volume 22, issue 2, 2012, Pages 195~205
DOI : 10.9720/kseg.2012.22.2.195
We evaluated the results of pumping tests, the amount of groundwater used by Protected Cultivation with Water Curtain (PCWC), and monthly depth to water table (DTW) at the Wangjeon-ri area, Nonsan City, to elucidate the cause of a decrease in pumping rate during the winter PCWC season. The transmissivity and storage coefficient at eight sites where the major aquifer is alluvium, vary from 119.9 to
, respectively. The pumping rate for PCWC during three months (Dec. to Feb.) averaged about
and the maximum water level in the area varied by about 10 m. Groundwater levels had fully recovered by August-five months after pumping for PCWC had ceased. These observations indicate that the pumping rate during the winter PCWC season was excessive compared with groundwater productivity in the area. Groundwater level in the central PCWC area varied from -3.0 to 4.38 m, exceeding the water level of the Nosung Stream for only three months (Aug. to Oct.). This result indicates that Nosung Stream recharges the area during the period from November to July. To solve the problem of reduced pumping rate during the winter PCWC season, it would be necessary to reduce the amount of groundwater used for PCWC or to develop an artificial recharge system using recycled groundwater.
Understanding of Surface Water-Groundwater Connectivity in an Alluvial Plain using Statistical Methods
Kim, Gyoo-Bum ; Son, Young-Chul ; Lee, Seung-Hyun ; Jeong, An-Chul ; Cha, Eun-Jee ; Ko, Min-Jeong ;
The Journal of Engineering Geology, volume 22, issue 2, 2012, Pages 207~221
DOI : 10.9720/kseg.2012.22.2.207
A statistical analysis of time series of water level at 27 groundwater monitoring wells was conducted to analyze the surface water-groundwater connectivity in the wide alluvial plains surrounding the Nakdong River, Korea. Change in groundwater level is strongly related to river water level, yielding an average cross-correlation coefficient of 0.601, which is much higher than that between rainfall and groundwater level (0.125). Principal component analysis of groundwater level indicates that wells in the study area can be classified into two groups: wells in Group A are located close to a river, have water levels closely related to river level, and generally show a large increase in groundwater level during heavy rainfall. On the other hand, wells in Group B located far from a river are relatively less related to river level. Including hydrologic and statistical analyses, geochemical analysis and temperature monitoring are additionally required to reveal the relationship between surface water level and groundwater level, and to assess the possibility of groundwater flooding.
Use of the Risk Score for the Effective Management of Cut Slopes
Kim, Jin-Hwan ; Baek, Yong ; Koo, Ho-Bon ; Park, Keun-Bo ;
The Journal of Engineering Geology, volume 22, issue 2, 2012, Pages 223~231
DOI : 10.9720/kseg.2012.22.2.223
Many cut slopes are located near national highways, resulting in large annual damage to infrastructure from the collapse of cut slopes. Therefore, to effectively maintain cut slopes, high-risk slopes should be identified and monitored. In this paper, we evaluate the effectiveness of the management of cut slopes using the risk score calculated from cut-slope inventory data. The inventory survey, as a simple assessment of the characteristics of various slopes, was performed to collect basic data that could be obtained visually in the field for the management of cut slopes. This method is not a precise survey, and it was composed of the general status and characteristics of cut slopes, the inspector's assessment, and inventory data in order to estimate a risk score for each slope. In this paper, we calculated the risk score by investigating the present status of cut slopes adjacent to 10,461 national roads. In order to evaluate the effectiveness of using risk score data, we compared the score for stable slopes with those of failed cut slopes. Failed cut slopes occurred in sections with the highest risk score. The results show that risk score derived from the inventory survey of cut slopes are useful in the management of cut slopes with risk of failure and in monitoring large numbers of cut slopes.
Efficiency of Geothermal Energy Generation Assessed from Measurements of Deep Depth Geothermal Conductivity
Cho, Heuy-Nam ; Lee, Dal-Heui ; Jeong, Gyo-Cheol ;
The Journal of Engineering Geology, volume 22, issue 2, 2012, Pages 233~241
DOI : 10.9720/kseg.2012.22.2.233
The objectives of this study were to test geothermal conductivity (k), water velocity, water quantity, and pipe pressure from a ground heat exchanger in the field, and then to analyze these data in relation to the effectiveness and economical efficiency for application of geothermal energy. After installation of the apparatus required for field tests, geothermal conductivity values were obtained from three different cases (second, third, and fourth). The k values of the second case (506 m depth) and third case (151 m depth) are approximately 2.9 and 2.8, respectively. The k value of the fourth case (506 m depth, double pipe) is 2.5, which is similar to the second and third cases. This result indicates that hole depth is a critical factor for geothermal applications. Analysis of the field data (k, water velocity, water quantity, and pipe pressure) reveals that a single geothermal system at 506 m depth is more economically efficient than three geothermal systems at depths intervals of 151 m. Although it is more expensive to install a geothermal system at 506 m depth than at 151 m depth, test results showed that the geothermal system of the fourth case (506 m, double pipe) is more economically efficient than the system at 151 m depth. Considering the optional cost of maintenance, which is a non-operational expense, the geothermal system of the fourth case is economically efficient. Large cities and areas with high land prices should make greater use of geothermal energy.