• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.569-576
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• 2000

This study performs a series of Triaxial Compression Test for clay-sand composite specimens changing area replacement ratio. Purpose of the test is to conform the propriety of weighted average method in estimating shear strength of the composite ground. The test results show that measured values of shear strength of composite specimens are larger by 20∼30% than those from estimation using the current weighted average method. It is thought that the differences are from pseudo-overconsolidation behavior of composite specimens.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.02a
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• pp.71-78
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• 2000

SHANSEP method involves the consolidation to stresses in excess of the preconsolidation pressure in order to overcome sample disturbance effect. The concept of SHANSEP is based on an approach to laboratory test which attempts to reproduce the in-situ conditions more closely than is possible in routine tests and evaluates normalized strength parameters for the soil as a function of OCR. But SHANSEP method can be applied only to fairly uniform clay deposits, and is unsuitable for a random deposit. In this study, CK/sub o/U triaxial compression test and incremental loading consolidation test were performed for the application of SHANSEP method on Yangsan clay. During the K/sub o/-consolidation, triaxial specimens were consolidated to stress equal to two times the in-situ vertical effective stress. And for overconsolidated condition, the specimens were swelled to a known vertical effective stress in order to have the desired OCR. With the results of CK/sub o/U triaxial compression test using the block samples, the relationship between c/sub u//σ/sub vc/' and OCR on Yangsan clay was established. For evaluating the undrained shear strength of Yangsan clay with depth, CK/sub o/U triaxial compression test was performed using the piston samples taken from Yangsan site. And also undrained shear strength was analyzed from the in-situ test such as Cone Penetration Test(CPT), Dilatometer Test(DMT), and Field Vane Test(FVT) and was compared with that of CK/sub o/U triaxial compression test.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.2
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• pp.226-232
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• 2011

In this study, an optimized design of a triaxial load cell has been developed by the use of finite element analysis, design of experiment and response surface method. The developed optimal design was further validated by both stress-strain analysis and natural vibration analysis under an applied load of 30 kgf. When vertical, horizontal, and axial loads of 30 kgf were applied to the load cell with the optimal design, the calculated strains were satisfied with the required strain range of $500{\times}10^{-6}{\pm}10%$. The natural vibration analysis exhibited that the fundamental natural frequency of the optimally designed load cell was 5.56 kHz and higher enough than a maximum frequency of 0.17 kHz which can be applied to the load cell for wind-tunnel tests. The satisfactory sensitivity in all triaxial directions also suggests that the currently proposed design of the triaxial load cell enables accurate measurements of the multi-axial forces in wind-tunnel tests.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.852-855
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• 2010

Numerical simulations for large scale triaxial tests with large diameter rockfill materials are conducted using distinct element method. For generation of compacted assembly with specific grain size distribution and initial material porosity, the clump logic method and expansion of generated particles are adapted. With micro parameters which are chosen by calibration process, discrete particle modelling of triaxial test in case of other confining stress and cyclic loading condition were conducted. Also numerical simulations of fluid injection into particulate materials were conducted to observe cavity initiation and propagation using distinct element method. The fluid scheme solves the continuity and Navior-Stokes equations numerically, then derives pressure and velocity vectors for fixed grid by considering the existence of particles within the fluid cell.

• Geomechanics and Engineering
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• v.25 no.3
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• pp.253-266
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• 2021

In this paper, we discuss a mathematical method for determining the return energy of the wave from the sample and comparing it with the mechanical energy consumed to change the dimension of the sample in the triaxial test of the rock. We represent a method to determine the mechanical energy and then we provide how to calculate the return energy of the wave. However, the static energy and pulse return energy will show higher amounts with axial pressure increase. Three types of clastic sedimentary rocks including sandstone, pyroclastic rock, and argillitic tuff were selected. The sandstone showed the highest strength, Young's modulus and ultrasonic P and S waves' velocities versus others in the triaxial test. Also, from the received P wavelet, the calculated pulse wave returning energy indicated the best correlation between axial stress compared to wave velocities in all specimens. The fact that the return energy decreases or increases is related to increasing lateral stress and depends on the geological characteristics of the rock. This method can be used to determine the stresses on the rock as well as its in-situ modulus in projects that are located at high depths of the earth.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.431-438
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• 1999

An assessment of liquefaction potential is made in principle by comparing the shear stress induced by earthquake to the liquefaction strength of the soil. In this study, a modified method based on Seed and Idriss theory is developed for evaluating liquefaction potential. The shear stress in the ground can be evaluated with seismic response analysis and the liquefaction strength of the soil can be investigated by using cyclic triaxial tests. The cyclic triaxial tests are conducted in two different conditions in order to investigate the factors affecting liquefaction strength such as cyclic shear stress amplitude and relative density. And performance of the modified method in practical examples is demonstrated by applying it to liquefaction analysis of artificial zones with dimensions and material properties similar to those in a typical field. From the result, the modified method for assessing liquefaction potential can successfully evaluate the safety factor under moderate magnitude(M=6.5) of earthquake.

• Journal of the Korean GEO-environmental Society
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• v.22 no.4
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• pp.15-23
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• 2021

Various micropiles have been developed through research related to micropiles, which have been carried out with the increased use of micropiles. Among the micropile construction methods being developed, the triaxial micropile (tmp), which is recently developed for the purpose of increasing the horizontal bearing capacity (seismic resistance), is representative. The three-axis micropile has the advantage of a method that can resist horizontal load more effectively because three micropiles installed inclined on each axis resist horizontal load. However, there is a problem in effectively using this pile method due to insufficient research on the support characteristics of the triaxial group micropile. In order to effectively utilize the triaxial group micropile (tmp), it is required to evaluate the bearing capacity for the factors that affect the horizontal bearing capacity of the pile. Therefore, in this study, field horizontal loading Tests were performed for each load direction, field loading Tests were verified through three-dimensional finite element analysis, behavioral characteristics of triaxial micropiles were evaluated, and appropriate horizontal bearing capacity was analyzed in consideration of horizontal load directions.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.189-196
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• 2002

According to the Korean Design Code for port and harbor facilaties, bearing capacity of rubble mound under eccentric and inclined load is calculated by the simplified Bishop method, and strength parameters are recommended to be c=0.2kg/$\textrm{cm}^2$ and ø=35$^{\circ}$for standard rubble if the compressive strength of parent rock is greater than 300kg/$\textrm{cm}^2$, quoting from research results by Jun-ichi Mizukami(1991), But this facts have never been certified in Korea because there was not large-scale triaxial test apparatus until 2000 in Korea. Firstly in Korea, the large-scale triaxial test (sample diameter, 30cm and height, 60cm) on the rubble originated from porous basalt rock in North-Cheju was accomplished. Then strength parameters for basalt rubble produced in North-Cheju are recommended to be c=0.3kg/$\textrm{cm}^2$ and ø=36$^{\circ}$if the compressive strength of parent rock is greater than 400kg/$\textrm{cm}^2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1156-1163
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• 2014

In this work by measuring transfer impedance of communication cables using EN50289 its Shielding effect is analyzed. transfer impedance measurement triaxial method using EN50289 is defined in CENELEC, it is unlike triaxial method prescribed in IEC Standard 96-1, can be measured regardless of diameter of coaxial cable and outer conductor. in this paper, transfer impedance measurement device of coaxial cable is designed and made according to EN50289 standard, The analysis determines the reliable working frequency range of coaxial cable and examined the impact of different shielding methods on coaxial cable. The transfer impedance measurements show considerable variations in results with various shielding methods. also the measurement procedure is verified through comparison of calculated and measured transfer impedance of RG-58 cable.

• 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.