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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Geotechnical Society
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Journal DOI :
Korean Geotechical Society
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Volume & Issues
Volume 28, Issue 12 - Dec 2012
Volume 28, Issue 11 - Nov 2012
Volume 28, Issue 10 - Oct 2012
Volume 28, Issue 9 - Sep 2012
Volume 28, Issue 8 - Aug 2012
Volume 28, Issue 7 - Jul 2012
Volume 28, Issue 6 - Jun 2012
Volume 28, Issue 5 - May 2012
Volume 28, Issue 4 - Apr 2012
Volume 28, Issue 3 - Mar 2012
Volume 28, Issue 2 - Feb 2012
Volume 28, Issue 1 - Jan 2012
Selecting the target year
Local Uncertainty of the Depth to Weathered Soil at Incheon Songdo New City
Kim, Dong-Hee ; Ko, Sung-Kwon ; Lee, Woo-Jin ;
Journal of the Korean Geotechnical Society, volume 28, issue 11, 2012, Pages 5~16
DOI : 10.7843/kgs.2012.28.11.5
Since geologic data are often sampled at sparse locations, it is important not only to predict attribute values at unsampled locations, but also to assess the uncertainty attached to the prediction. In this paper, the assessment of the local uncertainty of prediction for the depth to weathered soil was performed by using the indicator kriging. A conditional cumulative distribution function (ccdf) was first modeled, and then E-type estimate was computed for the spatial distribution of the depth to the weathered soil. Also, optimal estimate of spatial distribution for the depth to weathered soil was determined by using ccdf and loss function. The design procedure and method considering the minimum expected loss presented in this paper can be used in the decision-making process for geotechnical engineering design.
Analytical Solution for Transient Groundwater Flow in Vertical Cutoff Walls : Application of Slug Test and Evaluation of Hydraulic Conductivity
Lim, Jee-Hee ; Lee, Dong-Seop ; Nguyen, The Bao ; Choi, Hang-Seok ;
Journal of the Korean Geotechnical Society, volume 28, issue 11, 2012, Pages 17~31
DOI : 10.7843/kgs.2012.28.11.17
No analytical solution exists for evaluating in-situ hydraulic conductivity of vertical cutoff walls by analyzing slug test results with consideration of transient flow. There is an analytical solution proposed to interpret a slug test performed in a partially penetrated well within an aquifer. However, this analytical solution cannot be directly applied to the cutoff wall because the solution has been developed exclusively for an infinite aquifer instead of a narrow cutoff wall. To consider the cutoff wall boundary conditions (i.e, constant head boundary and no flux boundary condition), the analytical solution has been modified in this study to take into account the narrow boundaries by introducing the imaginary well theory. Type curves are constructed from the currently derived analytical solution and compared with those of a partially penetrated well within an aquifer. The constant head boundary condition provides faster hydraulic head recovery curve than the aquifer case. On the other hand, no flux boundary condition leads to slower hydraulic head recovery. The bigger the shape factor and deviation of the well and the smaller the width of the vertical cutoff wall are, the more effect of boundary condition was observed. The type curves obtained from the analytical solution for a cutoff wall are similar to those made by the numerical method in the literature.
Load Sharing Analysis of Piled Rafts Based on Non-linear Load-Settlement Characteristics
Choi, Kyu-Jin ; Park, Dong-Gyu ; Lee, Jun-Hwan ;
Journal of the Korean Geotechnical Society, volume 28, issue 11, 2012, Pages 33~40
DOI : 10.7843/kgs.2012.28.11.33
The design of Piled Raft foundations considering the load sharing between raft and piles provides a more economical solution than the conventional design approach based on bearing capacity of piles only. Generally, numerical methods are used to analyze the behavior of Piled Rafts due to its complexity and load sharing ratio is also estimated by numerical methods about some limited cases under specific load level and soil conditions. In this study, a method to estimate the load sharing between the raft and piles was developed which is based on load-settlement characteristics of foundation elements. Normalized load-settlement curves of the raft and pile groups were derived individually, and the relationship between load sharing ratio and foundation settlement was proposed by using these curves. For each load-settlement curves, hyperbolic type was adopted in order to describe the non-linear behavior of foundations. Centrifuge test results were compared with the results from proposed method, and the trends of variation of load sharing ratio with settlement presented from both were similar.
The Consolidation Characteristics of Soft Clay by Stepped Vacuum Pressure in Individual Vacuum Method
Han, Sang-Jae ; Kim, Jong-Seok ; Kim, Byung-Il ; Kim, Do-Hyung ;
Journal of the Korean Geotechnical Society, volume 28, issue 11, 2012, Pages 41~52
DOI : 10.7843/kgs.2012.28.11.41
Suction drain method can directly apply vacuum pressure to the soft ground through vertical drains so it can make hardening zones around them. These hardening zones make steeply lower the discharge efficiency of the pore water with decreasing permeability. This paper considered a stepped vacuum pressure to minimize a hardening zone which is one of the important parameters that can decrease discharge efficiency. A series of laboratory tests were conducted in order to examine the effect of the hardening zones and to evaluate their effects to the ground improvements with varying durations which applied stepped vacuum pressures(-20kPa, -40kPa, -60kPa and -80kPa) with Busan marine clay. According to strength(CPT), water content test and theoretical investigation indicate a size of the hardening zone within 7cm and the decreasing ratio of permeability about 2.0~4.0. Also, the total settlements are larger for the stepped vacuum pressure than the instant vacuum loading. The application time with vacuum pressure is determined considering the geotechnical properties of the interested clays. Results of numerical analysis show that consolidation behavior is appropriate to measurement for considering hardening zones.
Seepage Analysis of Large-Scale Embankment Model by Revised TDR Sensor
Park, Min-Cheol ; Lee, Jong-Wook ; Kim, You-Seok ; Han, Heui-Soo ;
Journal of the Korean Geotechnical Society, volume 28, issue 11, 2012, Pages 53~67
DOI : 10.7843/kgs.2012.28.11.53
In this research, stainless steel and heat-shrinkage tube were used for new TDR sensing line to solve the problems of ordinary TDR system. The new TDR line improved the sensitivity of water content and endurance, and reduced the data noise. The saturation degree test and acryl model test were done by revised TDR sensor. From the results, without additional data filtering and quantitative analysis, the raw data were separated into 3 zones; saturated, unsaturated and dried zones easily. In addition, the revised TDR sensor was installed in large-scale embankment model to perform the seepage test. The raw data of the model tests showed the distributed seepage behaviors and separated zones clearly, which were almost the same tendencies as the lab test results.
Hydro-mechanical Behavior of Partially Saturated Soil Slopes under Rainfall
Kim, Jae-Hong ; Im, Jae-Seong ; Park, Seong-Wan ;
Journal of the Korean Geotechnical Society, volume 28, issue 11, 2012, Pages 69~78
DOI : 10.7843/kgs.2012.28.11.69
Conventional numerical analysis for rainfall-induced slope stability has been estimated by separating seepage and stress-strain behavior, respectively. Many researchers` models from commercial softwares and literatures define that partially saturated permeability is the only function of degree of saturation (or matrix suction) and then they do not consider hydraulic-mechanical characteristics for the analysis. However, in practice, the water flow processes in a deformable soil are influenced by soil skeleton movement and the pore water pressure changed due to seepage will lead to changes in stress and to deformation of a soil. The relationship between seepage and soil behavior causes a change of partially saturated permeability as well as saturated permeability with the lapse of time. Instability of partially saturated soil slopes due to infiltration would be analyzed from reduction of negative pore water pressure calculating the process of water flow based on predicted partially saturated permeability. Therefore, partially saturated permeability should be defined by the function of degree of saturation (or matric suction) and porosity. The paper presents the comparison between staggered and monolithic coupled analysis regarding seepage and stress deformation problems. As a result, the decrease in matric suction on soil slope from monolithic analysis is slower than that from staggered analysis.
A Study on Durability Test of Cemented Soils
Park, Sung-Sik ; Hwang, Se-Hoon ;
Journal of the Korean Geotechnical Society, volume 28, issue 11, 2012, Pages 79~86
DOI : 10.7843/kgs.2012.28.11.79
Cemented soils have been used for subbase or base materials of roads, backfill materials of retaining walls and cofferdam. Such cemented soils can be degraded due to repeated wetting and drying or various weathering actions. Unlike rocks, a standard method was not defined for evaluating the durability of cemented soils. In this study, a slaking durability test and an ultrasound cleaner were used for developing a new durability test method for cemented soils. For durability tests, cemented sands with different cement ratios (4, 6, 8, and 12%) with cylindrical specimens were prepared and then air cured or under-water cured for three days. Three-day-cured specimens were dried for one day and then submerged for one day before testing. The weight loss after the slake durability test or ultrasonic cleaner operation for 10 or 20 min was measured and used for assessing durability. When a cement ratio was 4%, the weight loss from ultrasonic cleaner test was 7-25% but that from slake durability test was as much as 30-60%. For specimens with cement ratio of more than 8%, the weight loss was less than 10% from both tests. A durability index increased with increasing a cement ratio. The durability index of under-water cured specimen was higher than that of air cured specimen. The ultrasonic cleaner test was found to be an effective tool for durability assessment of cemented sands rather than the slake durability test.
A Study on Decreasing Behavior of Strength ＆ Elastic Parameters due to Water Infiltration in Rock Cores (II)
Cho, Hong-Je ; Jeong, Il-Soo ; Moon, Jong-Kyu ;
Journal of the Korean Geotechnical Society, volume 28, issue 11, 2012, Pages 87~99
DOI : 10.7843/kgs.2012.28.11.87
Targeting 9 types of rocks, which have high frequency of excavation, the researcher has analyzed decreasing behaviors of elastic modulus due to water content. The elastic modulus decreasing behaviors have been classified into 5 steps by uniaxial compressive strength. The results indicate that all of 5 sedimentary rocks and andesite show single decreasing behavior and granite, rhyolite, and gneiss demonstrate another decreasing behavior. Moreover, sensitivity of water content in granite, rhyolite, gneiss is almost twice as fast as that of the other rocks and their residual value of elastic modulus is very low.