• Geomechanics and Engineering
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• v.22 no.1
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• pp.97-108
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• 2020

The time-consuming and less objectivity are the main problems of conventional micromechanical parameters calibration method of Particle Flow Code simulations. Thus this study aims to address these two limitation of the conventional "trial-and-error" method. A new calibration method for the linear parallel bond model (CM-LPBM) is proposed. First, numerical simulations are conducted based on the results of the uniaxial compression tests on limestone. The macroscopic response of the numerical model agrees well with the results of the uniaxial compression tests. To reduce the number of the independent micromechanical parameters, numerical simulations are then carried out. Based on the results of the orthogonal experiments and the multi-factor variance analysis, main micromechanical parameters affecting the macro parameters of rocks are proposed. The macro-micro parameter functions are ultimately established using multiple linear regression, and the iteration correction formulas of the micromechanical parameters are obtained. To further verify the validity of the proposed method, a case study is carried out. The error between the macro mechanical response and the numerical results is less than 5%. Hence the calibration method, i.e., the CM-LPBM, is reliable for obtaining the micromechanical parameters quickly and accurately, providing reference for the calibration of micromechanical parameters.

• Journal of Ocean Engineering and Technology
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• v.22 no.4
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• pp.51-58
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• 2008

The objective of this study was to investigate the mechanical characteristics of fiber-reinforced lightweight soil using waste fishing net or monofilament for recycling both dredged soils and bottom ash. Reinforced lightweight soil consists of dredged soil, cement, air foam, and bottom ash. Waste fishing net or monoiament was added the mixture in order to increase the shear strength of the lightweight soil. Test specimens were fabricated with various mixing conditions, including waste fishing net content and monofilament content. Several series of unconfined compression tests and direct shear tests were carried out. From the experimental results, it was found that the unconfined compressive strength, as well as the stress-strain behavior of reinforced lightweight soil was strongly influenced by mixing conditions. In this study, the maximum increase in shear strength was obtained with either a 0.5% content of monofilament or 0.25% waste fishing net. The unconfined compressive strength of reinforced lightweight soil with monofilament was greater than that of reinforced lightweight soil with waste fishing net.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1412-1419
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• 2005

Preventing the infiltration of rainwater into the landfill site is the main purpose of the final cover in landfill sites. Compacted clay layer or geomembrain have been used as a conventional landfill final cover. But they have several disadvantages when damages might occur due to puncturing, differential settlement and desiccation or freeze and thaw. For this reason, as an alternative method SRSL(Self Recovering Sustainable Liner) has been developed. Adopting the precipitation reaction of two chemical material, by forming precipitates that fill the pores, and lower the overall permeability of the liner. The advantage of this method is that when fracture of the liner occurs the remaining reactants of the two layers form precipitates that fill the fracture and recover the low permeability of the liner. In this study, the recovering ability of the SRSL with a crack due to the seasonal variation or differential settlements was investigated by permeability tests. And in order to estimate the durability of the SRSL after freeze/thaw and desiccation, uniaxial compression strength tests were performed.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.407-414
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• 2004

Interfacial properties between rock mass and shotcrete play a significant role in the transmission of loads from the ground to shotcrete. These properties have a major effect on the behaviours of rock mass and shotcrete. They, however, have merely been assumed in most of numerical analyses, and little care has been taken in identifying them. This paper aimed to identify interfacial properties including cohesion, tension, friction angle, shear stiffness, and normal stiffness, through direct shear tests as well as interface normal compression tests for shotcrete/rock cores obtained from a tunnel sidewall. Mechanical properties such as compression strength and elastic modulus were also measured to compare them with the time-dependent variation of interfacial properties. Based on experiments, interfacial properties between rock and shotcrete showed a significant time-dependent variation similar to those of its mechanical properties. In addition, the time-dependent behaviours of interfacial properties can be well regressed through exponential and logarithmic functions of time.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1229-1241
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• 1994

This study aims at investigating the undrained behavior of the normally consolidated clay foundation using single hardening constitutive model based on elasticity and plasticity theories. The specimen employed was sampled at Mooan near the down stream of Young San river and remolded into consolidation apparatus. 11 soil parameters for the model was determined from simple tests such as isotropic compression and consolidation undrained triaxial compression tests. FEM program to predict the undrained behavior of the foundation was developed and back analysis was performed to verify prediction ability of the FEM program. Finally plate load test on the 2-dimensional model foundation was carried out in order to compare numerical analysis and observed values on the foundation.

• Steel and Composite Structures
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• v.16 no.4
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• pp.437-454
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• 2014

The influence of spacers on the behaviour and ultimate capacity of intermediate length CFS open section columns under axial compression is investigated in this paper. The focus of the research lies in the cross- section predominantly, failed by distortional buckling. This paper made an attempt to either delay or eliminate the distortional buckling mode by the introduction of transverse elements referred herein as spacers. The cross-sections investigated have been selected by performing the elastic buckling analysis using CUFSM software. The test program considered three different columns having slenderness ratios of 35, 50 & 60. The test program consisted of 14 pure axial compression tests under hinged-hinged end condition. Models have been analysed using finite element simulations and the obtained results are compared with the experimental tests. The finite element package ABAQUS has been used to carry out non-linear analyses of the columns. The finite element model incorporates material, geometric non-linearities and initial geometric imperfection of the specimens. The work involves a wide parametric study in the column with spacers of varying depth and number of spacers. The results obtained from the study shows that the depth and number of spacers have significant influence on the behaviour and strength of the columns. Based on the nonlinear regression analysis the design equation is proposed for the selected section.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.185-195
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• 2010

This paper presents the experiment results for a CFT column confined by carbon fiber sheets(CFSs) under an axial load. Nine specimens were constructed and axial compression tests were conducted. The main experiment parameters were diameter-thickness ratio(D/t), reinforcing CFSa, and the attachment of a cushion gap between surface of steel tube and CFSs. The load-displacement curves of the specimens were obtained from the compression tests. Finally, it was concluded that the CFT column with a gap had grater ductility capacity improvement that the CFT column confined by CFSs.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.5-13
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• 2004

Strength and compressibility characteristics of Light-Weighted Foam Soil (LWFS) are experimentally investigated in the paper. LWFS is composed of the dredged soils, cement and air foam to reduce unit-weight and to increase compressive strength. For these purposes, both unconfined compression tests and triaxial compression tests are carried out fer artficially prepared specimens of LWFS with various initial water contents, cement contents, mixing ratio of silty dredged soils and different confining stresses. The experimental results of LWFS indicate that the stress-strain relationship and the compressive strength are strongly influenced by cement contents rather than intial water contents of the edged soils. In this paper, the normalizing scheme considering the ratio of initial water contents, cement contents, and air foam contents has been proposed to evaluate the relationship between compressive strength of LWFS and a normalized factor.

• Journal of the Korean Geosynthetics Society
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• v.10 no.3
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• pp.9-18
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• 2011

This paper presents shear characteristics of a ground improved by sand piles. The sand piles have different length and diameter depending on the depth of a clayey layer. A series of CU triaxial compression tests are carried out on specimens covered with/without soft material which is similar to geotextile. The results show that the shear strength and stress ration increase as the length and the diameter of the sand pile increase. In addition, covering the specimen with the soft material appears to affect those characteristics as well. The increase of cohesion seems to be more remarkable compared to internal frictional angle.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.183-189
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• 1999

A numerical analysis was performed to predict flow curves and dynamic recrystallization behaviors of Al-5wt%Mg alloy on the basis of results of hot compression tests. The hot compression tests were carred out in the ranges of 350 ~ 500 ${^\circ}C$ and 5 ${\times}{10^-3}$ ~ 3 ${\times}{10^0}$/sec to obtain the Zener-Hollomon parameter Z. The modelling equation for flow stress was a function of strain, strain rate, temperature. The influence of these variables was quantifield using the Zener-Hollomon parameter. In the modelling equation, the effects of strain hardening and dynamic recrystallization were taken into consideration. Therefore, the modelling stress-strain curves of Al-5wt%Mg alloy were in good agreement with experimental results. Finally, the dynamic recrystallization kinetics were illustrated through the inspection of microstructure after deformation.