• Journal of the Korean Geotechnical Society
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• v.35 no.8
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• pp.5-15
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• 2019

This study was conducted to propose a reasonable requirement regulation of cutoff barriers composed of bottom layer and vertical barrier of offshore landfill for the prevention of contaminant leakage. The bottom layer was composed of impermeable clay layer; vertical walls were composed of double walls; outer wall was composed of steel sheet pile which registed against outer force; cutoff vertical barrier took the role of inner wall. Seepage-advection-dispersion numerical analysis was conducted using SEEP/W and CTRAN/W programs under steady and unsteady flows. The results showed that the values calculated under steady flow showed higher migration of pollutant than those of unsteady flow. The values calculated under steady flow are more valid from a design point of view. Under steady flow and the bottom clay layer and when the vertical barrier are homogeneous and completely well installed, respectively, the minimum required cutoff regulations for hydraulic conductivity, thickness, and embedded depth of the bottom clay layer and vertical barrier were suggested.

• Journal of the Korean Geotechnical Society
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• v.35 no.2
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• pp.5-17
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• 2019

Dynamic centrifuge model test was conducted to evaluate the dynamic stability of the pile-supported slab track method during dynamic railway loading and earthquake loading. The centrifuge tests were carried out for various condition of embankment height and soft ground depth. Based on test results, we found that the bending moment was increased with embankment height and decreased with soft ground depth. In addition, it was confirmed that the pile-supported slab track system could have dynamic stability for short-period seismic loading. However, in case of long-period seismic loading, such as Hachinohe earthquake, the observed maximum bending moment reached to pile cracking moment at the return period of 2,400 year earthquake. The criterion of ratio between embankment height and soft ground depth was suggested for dynamic stability of pile-supported slab track system.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.17-25
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• 2020

The artificial ground freezing method is a ground amelioration technology that does not have a permanent effect on the ground. One of the key factors that determine the efficiency and design criteria of the artificial ground freezing is the groundwater flow. Therefore, in order to accurately evaluate the behavior of the artificial ground freezing, studies on the effect of water flow on the formation of ice walls must be preceded. In this paper, experimental and numerical analyses were conducted using only pure water to maximize the effect of water flow on the formation of ice walls. A hydro-thermal coupled model for freezing behavior was proposed and the accuracy of the model was verified. Through the numerical and experimental studies, the flow rate dominates not only the formation time but also the shape of the ice wall. In addition, this study proposes a method to indirectly predict the ice wall formation time, which is expected to be highly useful for a practical application where it is difficult to visually identify ice walls.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.87-97
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• 2020

Recently, interest in Tie-cell wave-dissipating blocks that can compensate for the disadvantages of block-type breakwaters and provide economically effective design is increasing. Tie-cell wave-dissipating block has high activity resistance due to its structure in which each block is held together by a pile. In this study, through the laboratory model experiments, it was possible to confirm the increase in lateral resistance of the Tie-cell wave-dissipating blocks due to the penetration of the piles. The lateral resistance of the piles appeared almost constant regardless of the overburden load of the blocks. The lateral resistance shared by the piles changed depending on the increase or decrease in the lateral resistance of the friction between blocks. In the experiment in which two piles were penetrated, the overall lateral resistance was larger than the case a single pile was used, but the resistance behavior of the piles was different.

• Journal of the Korean Geotechnical Society
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• v.37 no.7
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• pp.25-34
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• 2021

Since the dredging reclaimed land consisting of soft ground is very weak in support, the difficult and complex factors should be considered in the design to calculate accurate bearing capacity of soft ground. Recently, various reinforcement construction methods of soft ground have been designed for dredged landfills, but the stabilities are predicted by calculating conventional Meyerhof (1974) equation for trafficability in soft ground. Conventional equations increase economic costs by underestimating bearing capacity of weak ground in order to ensure constructive safety, so a modified equation has been proposed from the literature. The paper attempts to experiment and compute important factors, such as stitching fiber and seam tensile strength of geotextiles, that are not theoretically considered and can be identified in the field. In addition, The evaluation of the bearing capacity of the modified equation is verified to be stable for trafficability through the plate bearing test performed on site.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.17-27
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• 2022

To characterize the dynamic properties of Gimhae Plains sediments, we calculated natural frequencies using microtremor horizontal-to-vertical spectral ratios and derived shear wave velocity profiles by inversion of Rayleigh-wave dispersion curves obtained by the high frequency-wavenumber and modified spatial autocorrelation methods. Our results suggest that in this region, strong amplification of ground motion is expected in the vibration frequency (f ≥ 1 Hz). Additionally, obtained velocity profiles show that shear wave velocities are ~200 and 400 m/s for the shallow marine and old fluvial sediments, respectively. Bedrock is possibly encountered at depths of 60-100 m at most sites. We developed a simplified shear wave velocity model of shallow sediments based on the obtained profiles. Our results suggest that a large area in the Gimhae Plains could be categorized as an S6 site based on the Korean seismic design code (KDS 17 10 00).

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.39-52
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• 2022

Multilayer perceptron neural network was trained to determine the factor of safety and slip surface of the slope. Slope geometry is a simple slope based on Korean design standards, and the case of dry and existing groundwater levels are both considered, and the properties of the soil composing the slope are considered to be sandy soil including fine particles. When curating the data required for model training, slope stability analysis was performed in 42,000 cases using the limit equilibrium method. Steady-state seepage analysis of groundwater was also performed, and the results generated were applied to slope stability analysis. Results show that the multilayer perceptron model can predict the factor of safety and failure arc with high performance when the slope's physical properties data are input. A method for quantitative validation of the model performance is presented.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.29-37
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• 2022

A three-dimensional analysis is required to interpret the drainage behavior of an improved ground with vertical drains, and the macroelement method enables efficient interpretation considering the three-dimensional drainage effect of vertical drains under two-dimensional plane strain condition. In this study, a novel finite element analysis program was developed by applying the macroelement method to the vacuum consolidation method used in ground improvement practice. The conventional macroelement method was used to calculate the amount of drainage from the vertical drain by setting the excess porewater pressure in the drainage material to zero; however, the program developed in this study was improved to consider negative excess porewater pressure as an actual vacuum consolidation condition. To verify the performance of the program, because of a comparison with the measurement values at the site where the vacuum consolidation method was applied, results predicted by the program and field measurement data showed similar settlement behavior.

• Journal of the Korean Geotechnical Society
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• v.39 no.9
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• pp.25-33
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• 2023

To effectively improve soft soils, it is necessary to perform ground behavior characteristics and stability management through measurement activities when embankment of structures on soft soils is conducted. However, there are many differences between the actual ground behavior and the initial design plan. To address this issue, this study analyzed the measured settlement in the Yeongam-Haenam areas using the Hyperbolic method to predict the settlement based on the measurement data. From the completion time of the embankment in the target area, the final settlement was predicted through the change in the degree of consolidation by the measurement period. Furthermore, the final settlement according to the change in degree of consolidation was compared and analyzed through finite element analysis and field measurement.

• Journal of the Korean Geotechnical Society
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• v.39 no.4
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• pp.5-17
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• 2023

The advancement in large-scale underground excavation in urban areas necessitates monitoring and predicting technologies that can pre-emptively mitigate risk factors at construction sites. Traditionally, two methods predict the deformation of retaining walls induced by excavation: empirical and numerical analysis. Recent progress in artificial intelligence technology has led to the development of a predictive model using machine learning techniques. This study developed a model for predicting the deformation of a retaining wall under construction using a boosting-based algorithm and an ensemble model with outstanding predictive power and efficiency. A database was established using the data from the design-construction-maintenance process of the underground retaining wall project in a manifold manner. Based on these data, a learning model was created, and the performance was evaluated. The boosting and ensemble models demonstrated that wall deformation could be accurately predicted. In addition, it was confirmed that prediction results with the characteristics of the actual construction process can be presented using data collected from ground measurements. The predictive model developed in this study is expected to be used to evaluate and monitor the stability of retaining walls under construction.