• Journal of the Korean Geosynthetics Society
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• v.11 no.4
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• pp.71-77
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• 2012

In this study, data collected from geotechnical instrumentation, analyzers using Stochastic methods for evaluating the state of law and the automation program was developed. Is expected based data driven non-parametric methods modeling may be useful for evaluation of complex geotechnical instrumentation installed on the system from the measurements collected. Result of the verification of assessment techniques developed by the sensing data collected from the actual ground structures (reinforced retaining wall and tunnel), PCA analysis techniques applied to the present study was to determine the structural behavior and environmental factors.

• Land and Housing Review
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• v.8 no.1
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• pp.13-22
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• 2017

In this study, triggering mechanism of ground sinking was analyzed through groundwater flow analysis on the basis of a case of the ground sinking occurred in Yongsan in 2015. The results of geotechnical investigation performed before and after the ground sinking were analyzed for the accurate understanding of geological features in the study area. The numerical groundwater flow analysis was performed to evaluate the influence of the flow behavior from the surrounding area toward the excavated site using software of Visual MODFLOW. As a result, it was found from the geotechnical analysis that the strata of sedimentary layer along the sunken area in the vertical direction was mixed significantly after the ground sinking compared with the status of the soil condition before the ground sinking. Piping was occurred at the toe of cut-off wall in the sandy gravel layer, and this phenomenon was predicted by the numerical flow analysis. Sequential ground displacement scenario of the ground sinking was derived from the geotechnical in situ test and numerical flow analysis performed in this study.

• Geotechnical Engineering
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• v.12 no.4
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• pp.21-32
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• 1996

To predict the stress-strain behavior of the soil more approximately, the concept of the critical state soil mechanics was added to the plasticity increment theory in the bounding surface Plasticity model. This model was constituted with two ellipse and one hyperbola in older to describe the behaviour of the isotropically consolidated soil. Thus, this model is very complicate due to the various parameters used. Therefore, the accurate understanding and skill of the theory is required in order to apply this model to the practical geotechnical problems. In the present paper, the bounding surface shape paraiheter R and A, the mapping center parameter C among various parameters used were varied and the results were numerically analized. Finally, each sensitivity with respect to monotonic and cyclic loading was analized and the range of the value of the each parameter was proposed.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.514-527
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• 2007

Earth reinforcement techniques are used worldwide and offer proven solutions to a wide range of geotechnical engineering problems. Here in this paper, recent developments of three major reinforced soil retaining wall methods in Japan were introduced in order to show how the current situation of this technique in Japan is. And the statistical data for the volume of the use was also shown, such as the total volume of the use, the scales of the structures, layout of the earth reinforcement, fill materials, and foundation conditions. Some of the case histories were also introduced with photographs and figures. And then, as one of recent research activity by the author, the study on the application of X-ray CT for the problem of earth reinforcement method combined with other method such as piling and soil improvement was introduced. In this study, a series of model test for several reinforced ground with geogrids was conducted using a newly developed test apparatus. Then, the behavior in the soil box was scanned after settlement using X-ray CT scanner. Based on these test results, the reinforcing effect by the geogrids and the soil arching effect over the pile heads was discussed precisely and those are done in 3-D with nondestructive condition. Finally, the effectiveness of the use of X-ray CT scanner in geotechnical engineering was promised.

• Journal of Korean Society of Disaster and Security
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• v.10 no.1
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• pp.47-53
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• 2017

Accurate exploration of the risk factors of the ground subsidence is needed to predict and evaluate the subsidence of the surrounding ground due to the excavation of the ground. In this study, we analyzed the distribution of soil relaxation area by analyzing the behavior around the ground excavation site and simulated the GPR exploration under various conditions. As a result, Although there are some differences according to the water content, distribution of the strata and the distribution of the relaxation region were confirmed in the unsaturated soil, and it was found that there was a difficulty in the GPR exploration in the saturated soil.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.577-585
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• 2015

Contamination of soil due to an oil spill influences its subsequent behavior. An investigation was conducted to study the effect of oil viscosity on compaction characteristics, coefficient of permeability, and shear strength. Water permeability was also determined by using Kerosene, Engine oil, and Crude-oil as contaminants. The test results indicate that the compaction characteristics are influenced by oil contamination. Direct shear test was conducted to investigate the effect of oil in the pore space in sandy ground. angle of internal friction of sand (based on total stress condition) decreases due to presence of oil within the pore spaces in sand.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.57-64
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• 2007

Since matric suction of unsaturated soil was related to soil and ground water contaminations, it is very important to analyze its mechanism that was represented by shear characteristics. In three phases of soil, a little air makes the condition of unsaturated soil on contract or shrinkage surface between water and air. Capillarity and suction in pore of unsaturated soil cause surface tension and surface force so it makes negative pore water pressure and increases effective stress as a result. Therefore, negative pore water pressure in partially saturated soil affects the soil structure and degree of saturation and it is important to evaluate accurately unsaturate flow and behavior. In this study, the shear strength characteristics of the seven sandy soils were investigated using consolidated drained triaxial tests with special emphasis on the effects of the negative pore pressure and the matric suction. These tests involved shearing under either a constant net confining pressure and varying matric suction or under a constant matric suction and varying net normal stress.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.511-529
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• 2023

This paper aims to better understand the bonding behavior in Reinforced Concrete beams strengthened with an Ultra-High Performance Fiber Reinforced Concrete (RCUHPFRC) layer on the compression side using experimental tests and numerical analyses. The UHPFRC mix design was obtained through an optimization procedure, and the characterization of the materials included compression and slant shear tests. Flexural tests were carried out in RC beams and RC-UHPFRC beams. The tests demonstrated a debonding of the UHPFRC layer. In addition, 3D finite element analyses were carried out in the Abaqus CAE program, in which the interface is modeled considering a zero-thickness cohesive-contact approach. The cohesive parameters are investigated, aiming to calibrate the numerical models, and a sensitivity analysis is performed to check the reliability of the assumed cohesive parameters and the mesh size. Finally, the experimental and numerical values are compared, showing a good approximation for both the RC beams and the RC strengthened beams.

• Geomechanics and Engineering
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• v.37 no.1
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• pp.31-48
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• 2024

To stabilize the excavations in urban area, soil anchorage is among the very common methods in geotechnical engineering. A more efficient deformation analysis can potentially lead to cost-effective and safer designs. To this end, a total of 116 three-dimensional (3D) finite element (FE) models of a deep excavation supported by tie-back wall system were analyzed in this study. An initial validation was conducted through examination of the results against the Texas A&M excavation cases. After the validation step, an extensive parametric study was carried out to cover significant design parameters of tie-back wall system in deep excavations. The numerical results indicated that the maximum horizontal displacement values of the wall (δ_hm) and maximum surface settlement (δ_vm) increase by an increase in the value of ground anchors inclination relative to the horizon. Additionally, a change in the wall embedment depth was found to be contributing more to δ_vm than to δ_hm. Based on the 3D FE analysis results, two simple equations are proposed to estimate excavation deformations for different scenarios in which the geometric configuration parameters are taken into account. The model proposed in this study can help the engineers to have a better understanding of the behavior of such systems.

• Geotechnical Engineering
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• v.11 no.3
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• pp.27-36
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• 1995

Laboratory model tests to determine the permanent settlement of a surface strip foundati on supported by geogrid -reinforced saturated clay and subjected to a low -frequency cyclic load were performed. In conducting the test, the foundation was initially subjected to an allowable static load. The cyclic load was then super -imposed over the static load. The variation of the maximum permanent settlement with the intensity of the static load and the intensity of the amplitude of the cyclic load are also presented.