• Tunnel and Underground Space
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• v.14 no.3
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• pp.215-228
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• 2004

Rock mass contains discontinuities such as faults and joints, and their mechanical properties and spatial distribution dominate the stability of rock mass. Because the deformation of rock mass occurs discontinuities in many cases. However in the case of poor quality rock mass under high stresses, the deformation along intact rock can also influence the structure's stability. In this study, two dimensional finite element program was developed with a rheological model to analyze the stability of the structure excavated in jointed rock mass. The “equivalent material” approach was used assuming intact rock, joints and rock bolts as visco-plastic materials. The program was verified by analysing an intact rock model, a jointed rock mass model and a reinforced jointed rock mass model. The displacement was examined in each model with changing the intact rock behaviour as elastic and visco-plastic. In the case of poor quality rock mass under high stresses, e assumption of visco-plastic behaviour of intact rock resulted in larger displacement than when assuming elastic behaviour for intact rock. Therefore it is recommended to add intact rock's visco-plastic behaviour to the existing model, which only assumes visco-plastic behaviour of joints and rock bolts.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1050-1059
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• 2019

The self diffusion, hole volume, and flow thermodynamic parameters of polyamide fibers were calculated from rheological parameters and crystallite size in order to study of flow segments in amorphous region. The stress relaxation of polyamide filament fibers were carried out in air and various solvents at various temperatures using the tensile tester with the solvent chamber. The rheological parameters were obtained by applying the experimental stress relaxation curves to the theoretical equation of the Ree-Eyring and Maxwell non-Newtonian model. It was observed that the rheological parameters of these polyamide filament fibers are directly related to the relaxation spectra, self diffusion, viscosities, and activation energies of flow segments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.3
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• pp.75-84
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• 1991

When we construct the earth structures such as embankments, on soft ground which are consisted of thick marine silty clay, the foundations deform due to consolidation and creep. For the stabilization of the earth structures constructed on soft foundations, we usually uses the mattress and they play an important role in increasing an ultimate bearing capacity by the dispersion of load of embankment. The purpose of this paper was to predict rationally a long term deformation of earth structures and to contribute to embankment design and maintenance. We determined a rheological model of marine clay from experimental data, and developed a computer program using the chosen model and found out the long term behavior of embankment. The results of this paper are as follows: 1. The developed program can analyze simultaneously consolidation and creep. 2. From the results of creep test, the rheological model of marine silty clay can be represented by the Vyalov model. 3. The displacement of embankment on reinforced foundation were smaller than those of the unreinforced foundation in showing the effects of geotextiles on foundation deformations.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.196-202
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• 2006

The self diffusion distributions of viscoelastic molten polyurethanes were determined from the relationship between the relaxation spectra and the distribution of self diffusion. The relaxation spectra of ester, PCL and PCL dyed type molten polyurethanes were obtained by applying the experimental stress relaxation curves to the theoretical equation of the Ree-Eyring and Maxwell non-Newtonian model(REM model) from computer calculation. The experiments were carried out at various temperatures using the physica rheometer with the temperature controller. The self diffusion and hole distance of amorphous region of polyurethane samples were investigated by experiments of stress relaxation. The diffusion coefficients and hole volumes were calculated from rheological parameters and crystallite size in order to study the diffusion of flow segments in amorphous region. It was observed that the relaxation spectra and self diffusions of these polymer samples are directly related to the distribution of molecular weights, viscosities, hole volumes and activation energies of flow segments.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.300-303
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• 2010

The present study investigates the flow characteristics of simulant gel propellant(carbopol 0.5%wt) in a variety of injectors. Rheological data for gel propellant has been measured and injector flow characteristics for plain-orifice, chamfered-orifice and venturi type injector have been numerically analyzed. The apparent viscosity of plain-orifice and chamfered-orifice have tendency to increase along axial direction, whereas for venturi type injector, low viscosity has been achieved in the injector flow. This phenomenon was clearly pronounced as Reynolds number is increased.