• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.369-376
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• 2000

Parameters that represent the characteristic of consolidation have been determined by the oedometer tests. They are varied by the process of sampling and transportation, accuracy of apparatus, process of sample trimming and the skill of engineers. Also, it is difficult to grasp what factor exert a influence on the parameters. In this study, Slurry Rowe Cell Tests were peformed to evaluate the disturbance. Using the plot of e - log p which obtained from Rowe Cell test results, we compared the swelling indexes at the stress relief and the last loading stage. With that result, we tried to presume the disturbance of the 330 oedometer tests. The plot of compression-swelling index at the stress relief considerably scattered but at the last step of load shows a correlations between them. And the plot of depth-p$\sub$c/ shows a correlation with the different swelling indexes, but not in the LL-p$\sub$c/. Consequently, it is considered that the disturbance of the consolidation tests can be presumed by the comparison of the difference of swelling index.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.562-563
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• 2005

In case of aged porcelain, the failure in basic performance tests happened in cool-heat tests. Based on this characteristic, we studied the method predicting failure phenomena through more severe accelerated cool-heat ageing and accelerating thermal mechanical performance tests. Test results indicated that the thermal stress by temperature gradient was more severe parameter than thermal stress by quenching cycles within a category of standard or accelerating methods. And there is no the deterioration of statistic strength, but the deterioration of strength according to accelerating tests is serious.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.6
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• pp.615-626
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• 2019

In this study, the applicability of PHC pile jointing method using rectangular steel tubular was studied. PHC pile joints are welded and bolt assembly. The bolt assembly method is a method that improves the various problems of welded joints. Numerical analysis and tests were conducted to analyze the applicability of the PHC pile jointing method using a rectangular steel tubular. The tests were carried out to test the material properties of the rectangular steel tubular material and the bending test of the pile joints. The numerical analysis was interpreted in the same conditons as the tests conditions. As a result, the material strength of each rectangular steel tubular could be used as a joint material. In the bending test, it was evaluated as a sTable material above the allowable stress of piles. In the numerical analysis results under the same conditions as the tests, it was possible to apply the pile joint material without exceeding the allowable stress of the material.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.497-505
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• 2019

Biocementation based on the microbially induced calcite precipitation (MICP) process is a novel soil improvement method. Biocement can improve significantly the properties of soils by binding soil particles to increase the shear strength or filling in the pores to reduce the permeability of soil. In this paper, results of triaxial consolidated undrained (CU) tests and constant shear drained (CSD) tests on biocemented Ottawa sand are presented. In the CU tests, the biocemented sand had more dilative behaviour by showing a higher stress-strain curves and faster pore pressure reducing trends as compared with their untreated counterparts. In the CSD tests, the stress ratio q/p' at which biocemented sand became unstable was higher than that for untreated sands, implying that the biocementation will improve the stability of sand to water infiltration or liquefaction.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.151-160
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• 1999

A series of laboratory tests for the marine clay sampled under the sea of Kwangyang bay have been conducted. The main types of tests are the general index property tests, the oedometer tests and the triaxial compression tests in both undrained(CIU) and drained(CID) conditions. The clayey samples, classified as CL, CH with natural water content of 38.3~84.6% and liquidity index of 0.71~0.98, are in the normally consolidated state with O.C.R. of 1.0l~l.60. The undrained stress path from CIU tests can be normalized with isotropic consolidation pressure$(p_0)$ and equal shear strain contour is linear passing through the origin in the (q, p) plot. The undrained shear strain is found to be the only function of the stress ratio($\eta$) and linear with intercept in the ($\varepsilon/\eta,\eta$) plot. The built-up pore pressure normalized with pc is also linear with respect to $\eta$. and its slope is defined by ´C´ as a pore pressure parameter. Equations to predict the undrained stress path and the shear strain are proposed. It is proved that the proposed equations give better agreements to the measured values than the Cam-clay theories. The failure points of the stress path are located on the same C.S.L. in (q, p) plot during both CIU and CID tests, which justifies the concept of critical state theory.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.111-120
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• 2003

A new stress path test method, which is more suitable f3r evaluating settlements of clay deposits, was introduced. This new method is basically based on back pressure equalization concept and makes it possible to estimate deformations corresponding to all points on a specific stress path by only one test. As a result, deformation characteristics of a clay deposit can be predicted by a few tests and the more practical application of stress path method can be realized. In addition, anisotropic deformation behaviors following arbitrary stress paths also can be experimentally measured by this test method. Experimental applicability of the proposed method was confirmed by performing various stress path tests on remolded kaolinite samples and the actual process to evaluate overall deformation characteristics and settlements was also presented.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.137-146
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• 2006

Shear wave velocity of uncemented soil can be expressed as the function of effective stresses when capillary phenomenons are negligible. However, the terms of effective stresses are divided to the direction of wave propagation and polarization because stress states are generally anisotropy. The shear wave velocities are affected by parameters and exponents that are experimentally determined. The exponents are controlled contact effects of particulate materials(sizes, shapes, and structures of particles) and the parameters are changed contact behaviors between particles, material properties of particles, and type of packing(i.e., void ratio and coordination number). In this study, consolidation tests are performed by using clay, mica and sand specimens. Shear wave velocities are measured during consolidation tests to investigate the stress-induced and inherent anisotropies through bender elements. Results show the shear wave velocities depends on the stress-induced anisotropy for round particles. Furthermore the shear wave velocity is dependent on particle alignment under the constant effective stress. This study suggests that the shear wave velocity and the shear modulus should be carefully calculated and used for the design and construction of geotechnical structures.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.123-128
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• 2001

The creep constants which are used to the reference stress equations of creep damage were obtained to type 316LN stainless steel, and their determining methods were described in detail. Typical Kachanov and Rabotnov(K-R) creep damage model was modified into the damage equations with reference stress concepts, and the modified equations were applied practically to type 316LN stainless steel. In order to determine the reference stress value, a series of high-temperature tensile tests and creep tests were accomplished at $550^{\circ}C$ and $600^{\circ}C$. By using the experimental creep data, the creep constants used in reference stress equations could be obtained to type 316LN stainless steel, and a creep curve on rupture strain was predicted. The reference stress concept on creep damage can be utilized easily as a design tool to predict creep life because the process, which is quantified by the measurement of voids or micro cracks during creep, is omitted.

• Geotechnical Engineering
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• v.9 no.4
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• pp.83-92
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• 1993

A series of drained triaxial tests on sand was performed using the cubical triaxial appaiatus, in which three principal stress could be loaded independently. The test results indicated that the intermediate principal stress influenced on both stress strain behavior and strength of sand. The axial strain at failure decreased and volumetric strain increased with an increase of the intermediate stress under constant minor principal stress. The internal friction angle of sand increased in general with increase of the deviator stress ratio b(=(G.:-c, )1(G, -G, )) except slight decrease of the internal friction angle as b value approached to 1. Finally Lade's failure criterion presented good coincidence with the exper imental strengttL while Mohr Coulomb failure criterion underestimated the experimental strength.

• Korean Journal of Materials Research
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• v.31 no.3
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• pp.172-180
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• 2021

In this study, using the plasma spray method, tensile and compression fatigue tests are performed in saline solution to examine the effect of Ti undercoat on corrosion fatigue behavior of alumina-coated specimens. The alumina-coated material using Ti in the undercoat shows better corrosion fatigue strength than the base material in the entire stress amplitude range. Fatigue cracking of UT specimens occurs in the recess formed by grit-blasting treatment and progresses toward the base metal. Subsequently, the undercoat is destroyed at a stage where the deformation of the undercoat cannot follow the crack opening displacement. The residual stress of the UT specimen has a tensile residual stress up to about 100 ㎛ below the surface of the base material; however, when the depth exceeds 100 ㎛, the residual stress becomes a compressive residual stress. In addition, the inside of the spray coating film is compressive residual stress, which contributes to improving the fatigue strength characteristics. A hardened layer due to grit-blasting treatment is formed near the surface of the UT specimen, contributing to the improvement of the fatigue strength characteristics. Since the natural potential of Ti spray coating film is slightly higher than that of the base material, it exhibits excellent corrosion resistance; however, when physiological saline intrudes, a galvanic battery is formed and the base material corrodes preferentially.