Gye-Chun Cho

Bio: Gye-Chun Cho is an academic researcher from KAIST. The author has contributed to research in topics: Rock mass classification & Abrasive. The author has an hindex of 33, co-authored 222 publications receiving 4754 citations. Previous affiliations of Gye-Chun Cho include University of New South Wales & Georgia Institute of Technology.

Particle Shape Effects on Packing Density, Stiffness, and Strength: Natural and Crushed Sands

Abstract: The size and shape of soil particles reflect the formation history of the grains. In turn, the macroscale behavior of the soil mass results from particle level interactions which are affected by particle shape. Sphericity, roundness, and smoothness characterize different scales associated with particle shape. New experimental data and results from published studies are gathered into two databases to explore the effects of particle shape on packing density and on the small-to-large strain mechanical properties of sandy soils. In agreement with previous studies, these data confirm that increased angularity or eccentricity produces an increase in emax and emin. Furthermore, the data show that increasing particle irregularity causes a decrease in stiffness yet heightened sensitivity to the state of stress; an increase in compressibility under zero-lateral strain loading; an increase in the critical state friction angle cs; and an increase in the intercept of the critical state line there is a weak effect on the slope . Therefore, particle shape emerges as a significant soil index property that needs to be properly characterized and documented, particularly in clean sands and gravels. The systematic assessment of particle shape will lead to a better understanding of sand behavior.

Soil behaviour: The role of particle shape

Abstract: This manuscript reviews particle shape, its development in fine-grained soils (particle size D ~100μm), shape characterization, and the role of particle shape on fabric formation and macroscale soil properties. Shape-dependent microscale mechanisms are hypothesized to explain previously published studies as well as new soil behaviour data. Particle shape emerges as a significant parameter that needs to be properly characterized and documented.

Unsaturated particulate materials--particle-level studies

Abstract: Analyses and experiments are performed to gain further insight into the behavior of unsaturated particulate materials, with emphasis on the pendular stage. First, interparticle forces are computed based on Laplace's equation; soil particles are ideally considered spherical or flat to facilitate the identification of the most relevant factors that affect unsaturated soil behavior. Second, the small strain stiffness is continuously measured on specimens subjected to drying, and changes in stiffness are related to changes in interparticle forces; data show important differences with previously published trends based on remolded specimens. Third, microscale experiments are performed to assess the strain at menisci failure in multiple deformation modes; results indicate that the lower the water content, the lower the strain required to eliminate the effects of capillarity, therefore, while capillary forces affect small strain stiffness, they may not contribute to large strain stiffness or strength. Finally, the rate of menisci regeneration is studied after a perturbation; stiffness recovery decreases with decreasing water content, and full recovery may not be reached when the degree of saturation is low. Several phenomena associated with the evolution of capillary forces during drying are identified.

Introduction of Microbial Biopolymers in Soil Treatment for Future Environmentally-Friendly and Sustainable Geotechnical Engineering

Abstract: Soil treatment and improvement is commonly performed in the field of geotechnical engineering. Methods and materials to achieve this such as soil stabilization and mixing with cementitious binders have been utilized in engineered soil applications since the beginning of human civilization. Demand for environment-friendly and sustainable alternatives is currently rising. Since cement, the most commonly applied and effective soil treatment material, is responsible for heavy greenhouse gas emissions, alternatives such as geosynthetics, chemical polymers, geopolymers, microbial induction, and biopolymers are being actively studied. This study provides an overall review of the recent applications of biopolymers in geotechnical engineering. Biopolymers are microbially induced polymers that are high-tensile, innocuous, and eco-friendly. Soil–biopolymer interactions and related soil strengthening mechanisms are discussed in the context of recent experimental and microscopic studies. In addition, the economic feasibility of biopolymer implementation in the field is analyzed in comparison to ordinary cement, from environmental perspectives. Findings from this study demonstrate that biopolymers have strong potential to replace cement as a soil treatment material within the context of environment-friendly construction and development. Moreover, continuing research is suggested to ensure performance in terms of practical implementation, reliability, and durability of in situ biopolymer applications for geotechnical engineering purposes.

Particle Shape Effects on Packing Density, Stiffness, and Strength: Natural and Crushed Sands

Abstract: The size and shape of soil particles reflect the formation history of the grains. In turn, the macroscale behavior of the soil mass results from particle level interactions which are affected by particle shape. Sphericity, roundness, and smoothness characterize different scales associated with particle shape. New experimental data and results from published studies are gathered into two databases to explore the effects of particle shape on packing density and on the small-to-large strain mechanical properties of sandy soils. In agreement with previous studies, these data confirm that increased angularity or eccentricity produces an increase in emax and emin. Furthermore, the data show that increasing particle irregularity causes a decrease in stiffness yet heightened sensitivity to the state of stress; an increase in compressibility under zero-lateral strain loading; an increase in the critical state friction angle cs; and an increase in the intercept of the critical state line there is a weak effect on the slope . Therefore, particle shape emerges as a significant soil index property that needs to be properly characterized and documented, particularly in clean sands and gravels. The systematic assessment of particle shape will lead to a better understanding of sand behavior.

Physical properties of hydrate-bearing sediments

Abstract: [1] Methane gas hydrates, crystalline inclusion compounds formed from methane and water, are found in marine continental margin and permafrost sediments worldwide. This article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments. Formation phenomena include pore-scale habit, solubility, spatial variability, and host sediment aggregate properties. Physical properties include thermal properties, permeability, electrical conductivity and permittivity, small-strain elastic P and S wave velocities, shear strength, and volume changes resulting from hydrate dissociation. The magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate-bearing sediments to changes in mechanical, thermal, or chemical boundary conditions. These predictions are vital for mitigating borehole, local, and regional slope stability hazards; optimizing recovery techniques for extracting methane from hydrate-bearing sediments or sequestering carbon dioxide in gas hydrate; and evaluating the role of gas hydrate in the global carbon cycle.

Applications of soil physics.

Abstract: Keywords: Mecanique des sols ; Drainage ; Ecoulement souterrain Reference Record created on 2004-09-07, modified on 2016-08-08

Suction Stress Characteristic Curve for Unsaturated Soil

Abstract: The concept of the suction stress characteristic curve (SSCC) for unsaturated soil is presented. Particle-scale equilibrium analyses are employed to distinguish three types of interparticle forces: (1) active forces transmitted through the soil grains; (2) active forces at or near interparticle contacts; and (3) passive, or counterbalancing, forces at or near interparticle contacts. It is proposed that the second type of force, which includes physicochemical forces, cementation forces, surface tension forces, and the force arising from negative pore-water pressure, may be conceptually combined into a macroscopic stress called suction stress. Suction stress characteristically depends on degree of saturation, water content, or matric suction through the SSCC, thus paralleling well-established concepts of the soil–water characteristic curve and hydraulic conductivity function for unsaturated soils. The existence and behavior of the SSCC are experimentally validated by considering unsaturated shear strength data for a variety of soil types in the literature. Its characteristic nature and a methodology for its determination are demonstrated. The experimental evidence shows that both Mohr–Coulomb failure and critical state failure can be well represented by the SSCC concept. The SSCC provides a potentially simple and practical way to describe the state of stress in unsaturated soil.