• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.3
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• pp.70-81
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• 1996

Solutions of geotechnical engineering problems require predictions of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such predictions even for complicated problems. To get accurate results, realistic stress-strain relationships of soils are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. Isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress path for Baekma river sand were performed to investigate stress-strain and volume change characteristics of Lade's single work hardening model dependant on the stress path. In order to predicted of stress-strain and volumetric strain behavior were determined the values of parameters for the mode by the computer program based on the regression analysis. Predicted stress-strain behavior of triaxial compression tests and optional stress path tests for increasing confining pressure with parameters obtained conventional triaxial compression tests agreed with several test results but the prediction results for decreasing confining pressure reduced triaxial compression tests make a little difference with test results.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.2
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• pp.70-79
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• 1999

The lower ground of structure, in which the strip loads, such as earth dams and embankments , are signiificantly working on , is required to be interpreted as a state of plane strain where the strain of intermediated principal stress direction is put '0' . The plane strain state is frquently observed in actural soil engineering case. For those case, drained stress-strain and strength behavior of Iksan weathered granite soil prepared in cubical specimens with cross-anisotropic fabric was studied by conventional triaxial compression, plane strain and cubial triaxial tests with independent control of the three principal stress. All specimens were loaded under conditions of principl stress directions fixed and aligned with the directions of the material axes. As a result of research , when a ground condition is analyzed under plane strain state, the shear strength obtained from the conventional triaxial compression test can be understimated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.10 s.253
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• pp.1242-1248
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• 2006

Densification behavior of nanocrystalline titania powder was investigated under cold compaction. Experimental data were obtained under triaxial compression with various loading conditions. Lee and Kim proposed the Cap model by developing the parameters involved in the yield function of general Cap model and volumetric strain evolution under cold isostatic pressing. The parameters in the Drucker/Prager Cap model and the proposed model were obtained from experimental data under triaxial compression. Finite element results from the models were compared with experimental data for densification behavior of nanocystalline ceramic powder under cold isostatic pressing and die compaction. The proposed model agreed well with experimental data under cold compaction, but the Drucker/Prager Cap model underestimated at the low density range. Finite element results, also, show the relative density distribution of nanocystalline ceramic powder compacts is severe compared to conventional micron powder compacts with the same averaged relative density.

• Geomechanics and Engineering
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• v.23 no.3
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• pp.189-206
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• 2020

The accurate modeling of boundary conditions is important in simulations of the discrete element method (DEM) and can affect the numerical results significantly. In conventional triaxial compression (CTC) tests, the specimens are wrapped by flexible membranes allowing to deform freely. To accurately model the boundary conditions of CTC, new flexible boundary algorithms for 2D and 3D DEM simulations are proposed. The new algorithms are computationally efficient and easy to implement. Moreover, both horizontal and vertical component of confining pressure are considered in the 2D and 3D algorithms, which can ensure that the directions of confining pressure are always perpendicular to the specimen surfaces. Furthermore, the boundaries are continuous and closed in the new algorithms, which can prevent the escape of particles from the specimens. The effectiveness of the proposed algorithms is validated by biaxial and triaxial simulations of granular materials. The results show that the algorithms allow the boundaries to deform non-uniformly on the premise of maintaining high control accuracy of confining pressure. Meanwhile, the influences of different lateral boundary conditions on the numerical results are discussed. It is indicated that the flexible boundary is more appropriate for the models with large strain or significant localization than rigid boundary.

• Geomechanics and Engineering
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• v.28 no.2
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• pp.181-195
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• 2022

Roughness and joint inclination angle are the important factors that affect the strength and deformation characteristics of jointed rock mass. In this paper, 3D printer has been employed to make molds firstly, and casting the jointed specimens with different joint roughness coefficient (JRC), and different joint inclination angle (α). Conventional triaxial compression tests were carried out on the jointed specimens, and the influence of JRC on the strength and deformation parameters was analyzed. At the same time, acoustic emission (AE) testing system has been adopted to reveal the AE characteristic of the jointed specimens in the process of triaxial compression. Finally, the morphological of the joint surface was observed by digital three-dimensional video microscopy system, and the relationship between the peak strength and JRC under different confining pressures has been discussed. The results indicate that the existence of joint results in a significant reduction in the strength of the joint specimen, JRC also has great influence on the morphology, quantity and spatial distribution characteristics of cracks. With the increase of JRC, the triaxial compressive strength increase, and the specimen will change from brittle failure to ductile failure.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.644-655
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• 2008

Conventional hyperbolic model does not satisfactorily predict the overall stress-strain behaviors of various geomaterials. Tatsuoka and Shibuya(1992) suggest the generalized hyperbolic equation(GHE) considering strain dependency and calculated performance is in good agreement with precise triaxial compression test results of stress-strain relations over wide range of strains before peak stress condition in some cases, but GHE model also does not satisfactorily predict stress-strain relations as strain goes on state of peak stress in most cases. For improve a weak point of the GHE, in this study, modified form of generalized hyperbolic equation (MGHE model) is proposed which can predict highly nonlinear stress-strain behavior for various geomaterials from small strain to peak stress condition.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.679-686
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• 2010

Mechanical characteristics of bottom ash produced in coal-fired power plant are investigated to utilize as light-weight fill materials. Triaxial compression test, water retention test, and unsaturated direct shear test were conducted for weathered soil (WS), reclaimed bottom ash (RBA), and screened bottom ash (BA). RBA had larger frictional angle and lower effective cohesion than those of WS. Water retention charactersitics of RBA and BA existed within distributions of soil-water characteristic curves for domestic weathered soils. Unsaturated shear strength of RBA was similar to that of WS at matric suctions of 50 kPa and 100 kPa. As a conclusion, bottom ash can be used as fill materials to replace the conventional construction materials by.

• Geomechanics and Engineering
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• v.18 no.5
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• pp.459-469
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• 2019

It is important to estimate the shear strength of shallow compacted soils as a construction material. A series of constant water content triaxial compression (CWCC) tests under low confining state in this study were performed on compacted geomaterials. For establishing a relationship of the shear strengths between saturated and unsaturated states on compacted geomaterials, the suction stresses were derived by two methods: the conventional suction-measured method and the Suction stress-SWRC Method (SSM). Considering the suction stress as an equivalent confining stress component in the (${\sigma}_{net}$, ${\tau}$) plane, it was found that the peak deviator stress states agree well with the failure line of the saturated state from the triaxial compression test when the SSM is applied to obtain the suction stress. On the other hand, the cavitation phenomenon on the measurement of suction affected the results of the conventional suction-measured method. These results mean that the SSM is distinctly favorable for obtaining the suction value in the CWCC test because the SSM is not restricted by the cavitation phenomenon. It is expected that the application of the SSM would reduce the time required, and the projected cost with the additional equipment such as a pore water measuring device in the CWCC test.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.597-610
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• 2022

Knowledge of the failure behavior of friction materials considering their intermediate principal stress is related to an understanding of situations where these materials might be used: for example, the stability of deep-seated boreholes and fault slip analysis. This study designed equipment for physically implementing true triaxial compression and used it to assess specimens of plaster, a friction material. The material's mechanical behaviors are discussed based on the results. The applicability of the 3D failure criteria are also reviewed. The tested specimens were molded cuboids of width, length, and height 52, 52, and 104 mm, respectively. A total of 24 true triaxial compression tests were performed under various combinations of 𝜎₃ and 𝜎₂ conditions. Conventional uniaxial and triaxial compression tests were employed to estimate the mechanical properties of the plaster for use as parameters for 3D failure criteria. Examining the stress-strain relations of the plaster materials showed that a large difference between the intermediate principal stress and the minimum principal stress indicated strong brittle behavior. The mechanical behavior of the plaster used here reflects the change of intermediate principal stress. Nonlinear multiple regression analysis on the test data in the principal space showed that the modified Wiebols-Cook failure criterion and the modified Lade failure criterion were the most suitable 3D failure criteria for the tested plaster.

• Geotechnical Engineering
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• v.9 no.2
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• pp.27-40
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• 1993

This paper proposes a new procedure carrying out a series of consolidated-undrained triaxial tests with a specimen. In this procedure high confining pressure applied to the specimen keeps constant during the test and each stage of consolidation can be controlled by partial drainage. With this procedure the test time is remarkably reduced by performing a series of triaxial tests with a single specimen. In order to verify the appliesbility of the procedure, standard triaxial compression tests and conventional multi -stage triaxial testy are performed for both undisturbed and disturbed samples and the results are compared with those of the proposed procedure. The comparison shows that strength parameters determined by the proposed procedure are well agreed with those of the other tests and thus it can be said that the procedure is very effective and practical in determining strength parameters.