• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.13-21
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• 2002

A new method called S-SRICOS is proposed to predict the local scour depth around bridge piers. The S-SRICOS method is a simplified version of the SRICOS method which was developed to predict the scour depth versus time curve around bridge piers. The SRICOS method which considers the time effect based on the soil properties and the hydraulic parameters can handle a multi-flood hydrograph and multi-layer soil systems with the SRICOS program. An attempt was made to simplify the method to the point where only hand calculations would be required. The concept of the equivalent time was developed leer this purpose. The S-SROICOS method requires only 4 parameters such as pier width, design bridge life, design velocity corresponding to the design bridge life, and initial scour rate of the soil. The S-SRICOS method was verified against 55 cases of the scour depth results using the SRICOS method.

• Geomechanics and Engineering
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• v.23 no.1
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• pp.1-13
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• 2020

To give a solution for seismic stability of tunnel faces subjected to earthquake ground shakings, the pseudo-dynamic approach is originally introduced to analyze tunnel face stability in this study. In the light of the upper-bound theorem of limit analysis, an advanced three-dimensional mechanism combined with pseudo-dynamic approach is proposed. Based on this mechanism, the required support pressure on tunnel face can be obtained by equaling external work rates to the internal energy dissipation and implementing an optimization searching procedure related to time. Both time and space feature of seismic waves are properly accounted for in the proposed mechanism. For this reason, the proposed mechanism can better represent the actual influence of seismic motion and has a remarkable advantage in evaluating the effects of vertical seismic acceleration, soil amplification factor, seismic wave period and initial phase difference on tunnel face stability. Furthermore, the pseudo-dynamic approach is compared with the pseudo-static approach. The difference between them is illustrated from a new but understandable perspective. The comparison demonstrates that the pseudo-static approach is a conservative method but still could provide precise enough results as the pseudo-dynamic approach if the value of seismic wavelengths is large or the height of soil structures is small.

• Journal of the Korean Geotechnical Society
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• v.32 no.3
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• pp.49-60
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• 2016

Soil failure is initiated and preceded by forming and progressing of shear band, defined as the localization of deformation into thin zones of soil mass. To understand the failure mechanism of normally consolidated cohesive soil, the spatial distribution and evolution of deformation within the entire specimen need to be evaluated. In this study, vertical compression tests under plane strain condition were performed on reconstituted kaolinite specimens, while capturing digital images of the specimen at regular intervals during shearing. Overall stress-strain behavior from initial to post peak has been analyzed together with spatial distributions of deformations and shear band characteristics from digital images at 4 stages.

• Geomechanics and Engineering
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• v.22 no.3
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• pp.245-254
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• 2020

The interaction between the frozen soil and building structures deteriorates with the increasing temperature. A nuclear magnetic resonance (NMR) stratification test was conducted with respect to the unfrozen water content on the interface and a shear test was conducted on the frozen soil-structure interface to explore the shear characteristics of the frozen soil-structure interface and its failure mechanism during the thawing process. The test results showed that the unfrozen water at the interface during the thawing process can be clearly distributed in three stages, i.e., freezing, phase transition, and thawing, and that the shear strength of the interface decreases as the unfrozen water content increases. The internal friction angle and cohesive force display a change law of "as one falls, the other rises," and the minimum internal friction angle and maximum cohesive force can be observed at -1℃. In addition, the change characteristics of the interface strength parameters during the freezing process were compared, and the differences between the interface shear characteristics and failure mechanisms during the frozen soil-structure interface freezing-thawing process were discussed. The shear strength parameters of the interface was subjected to different changes during the freezing-thawing process because of the different interaction mechanisms of the molecular structures of ice and water in case of the ice-water phase transition of the test sample during the freezing-thawing process.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.41-53
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• 2014

This study examined the magnitude and distribution of the earth pressure on the support system in a jointed rock mass by considering different joint shear strength, rock type, and joint inclination angle. The study particularly focused on the effect of joint cohesive strength for a certain condition. Based on a physical model test (Son and Park, 2014), extended parametric studies were conducted considering rock-structure interactions based on the discrete element method, which can consider the rock and joint characteristics of rock mass. The results showed the earth pressure was strongly affected by the joint cohesive strength as well as the rock type and joint inclination angle. The study indicated that the effect of joint cohesive strength was particularly significant when a rock mass was under the condition of joint sliding. This paper investigates the magnitude of joint cohesive strength to prevent a joint sliding for each different condition. The test results were also compared with Peck's earth pressure, which has been frequently used for soil ground. The comparison indicated that the earth pressure in a jointed rock mass can be significantly different from that in soil ground. This study is expected to provide a better understanding of the earth pressure on the support system in a jointed rock mass.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.1
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• pp.45-52
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• 1982

A theoretical equation is presented to estimate lateral earth pressures acting on piles in a row in cohesive soil. Then. a series of model tests are carried out for various conditions of the piles and the soil to check the validity of the theoretical equation. As a result of the model tests, the validity of an assumption on the plastic state of soil made in the theoretical derivation and the significance of the theoretical values are clarified. And. the experimental and theoretical values give very good agreements for various kinds of soil strength, pile diameters and intervals between piles. Consequently, the theoretical equation can be used to estimate the lateral earth pressures acting on piles in a row when the soil just around piles become a plastic state.

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.13-22
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• 2011

In this study, features of correlation between S-velocity and N value are derived from 9 suspension PS layers in Chungcheong Buk-do. S-velocity to be measured on Chungcheong Buk-do is classified into 5 as conditions of stratum that are ; cohesive soil layer, sandy soil layer, gravel layer, weathering soil layer, weathered rock layer. Each correlation formulas between N value by SPT and S-velocity is proposed from these classifications. And correlation formula for whole soil body except weathered rock layer also is proposed for reference. Corelation formulas developed this study formed square expression considering existing formulas produced internationally. Strength parameter converted to linear if N value is more than 50. Features of proposed formula which came up with comparative analysis of international result of cohesive soil layer and sandy soil layer and gravel layer show similar to existing ones. But there is deference that result of correlation formula for weathered rock layer is a little smaller than domestic formula's one. Because correlations of weathered rock layer above the N value of 50 is converted into a linear formation.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.185-197
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• 2007

Limit analysis of upper and lower bound solutions has been well developed to provide the stability numbers for shallow tunnels in cohesive soil ($c_u$ material), cohesive-frictional soil (c'-$\phi$' material) and cohesionless soil ($\phi$'material). However, an extension of these methods to relatively deep circular tunnels in the cohesionless soil has been explored rarely to date. For this reason, the closed-form analytical solutions including lower bound solution based on the stress discontinuity concept and upper bound solution based on the kinematically admissible failure mechanism were proposed for assessing tunnel collapse load in this study. Consequently, the tunnel collapse load from those solutions was compared with both the finite element analysis and the previous analytical bound solutions and shown to be in good agreement with the FE results, in particular with the FE soil elements located on the horizontal tunnel axis.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.1
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• pp.82-90
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• 2007

In order to analyse the strength problems for an unsaturated soil, it is required to examine closely the characteristics of the parameters of shear strength which was changed with the metric suction and void ratio. To this ends, a triaxial compression test was conducted on the three samples-granular soil, cohesive soil and silty soil. The specimen was made by pressing the static pressure on the mold filled soil and was controled the void ratio with the different compaction ratio. And the test was performed by using the modified apparatus of the triaxial compression tester. The range of matric suction was 0-90 kPa.The measured results for the deviator stress and parameters of shear strength were analysed with the void ratio and the compaction ratio, and they were examined closely the characteristics of the strength for an unsaturated soil.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.4
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• pp.35-41
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• 2005

In order to analyse the flow problems for an unsaturated soil, it is required to examine closely the characteristics of the coefficient of permeability which is changing with the matric suction. To this ends, a permeability test was conducted on the three samples;granular soil, cohesive soil and silty soil. The specimen was made by pressing the static pressure on the mold filled with soil and the void ratio was controled with the different compaction ratio. And the test was performed by using the modified apparatus of the steady state method which was proposed by flute (1972). The range of matric suction was 0-90 kPa. The measured results for the coefficients of permeability were analysed with the void ratio and the compaction ratio, and it was examined closely the characteristics of the permeability for an unsaturated soil.