• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1109-1114
• /
• 2008

To investigate the effect of sample size on coefficient of consolidation of non-homogeneous soil, the result of a large size consolidation test using a huge undisturbed sample with $1200mm(D){\times}2000mm(H)$ in dimension is compared with that of oedometer test using undisturbed small sample. In addition, test results are compared with those of same test using remold sample. Experimental results show that, due to the lump of sand/silt was mixed in sample, the coefficient of consolidation of undisturbed samples have a difference for each tests. Whereas, the difference of coefficient of consolidation between remolded large and small samples is not found. Because sample size affects the test results, sample must be carefully selected for non-homogeneous soil.

• Journal of the Korean Society of Safety
• /
• v.25 no.2
• /
• pp.55-64
• /
• 2010

Since various weathered soils are encountered in many domestic construction sites, it is necessary to estimate characteristics of natural weathered soils. However, the remolded sample of weathered soils are commonly used to estimate their characteristics because it is very difficult to sample weathered soils in undisturbed states. However, it is well known that the behavior of remolded sample is different from that of the undisturbed sample particularly in the dynamic response, because the particle structure of undisturbed sample maintains its original structure from the mother rock. Thus, to evaluate the influence of sampling method and preparation method on stress-strain behavior, the resonant column tests were performed on the block, tube samples, remolded samples with static compression and remolded samples with tamping of the weathered granite soils. The shear modulus of the remolded sample with tamping is larger than the other samples presumably due to the high tamping pressure enough to induce particle breakage. The tube samples show larger damping ratios than other samples. Furthermore, one-dimensional ground response analysis was performed to compare the results qualitatively.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2003.03a
• /
• pp.725-732
• /
• 2003

It was achieved that Rowecell test for this undisturbed sample was picked by Block sampler($\phi$:250mm, L:500mm) and hydraulic piston sampler($\phi$:76mm, L:850mm) in the marine clay of YONGYUDO and YEONGJONGDO in this research. Ratio of coefficient of consolidation was analyzed through comparison with C$\_$h/ by CPTu and C$\_$v/ and C$\_$h/ by existent consolidation test. According to analysis, coefficient of consolidation of block sample is fairly greater than coefficient of consolidation of piston sample. And the bigger diameter of undisturbed sample, sample disturbance could know decreasing. Coefficient of consolidation by Rowecell test measured more greatly than coefficient of consolidation by existent consolidation test. Rowecell test could know decreasing consolidation rate because of smear effect by Mandrel injection. Also, C$\_$h/ by CPTu shows deviation by each analysis method, selection of suitable analysis method judged by important leading in the coefficient of consolidation.

• Journal of the Korean Geotechnical Society
• /
• v.37 no.12
• /
• pp.107-116
• /
• 2021

In this study, a set of laboratory liquefaction test has been conducted using undisturbed samples collected from Songlim-park, Pohang where liquefaction phenomenon had been observed in 2017. Soil samples were frozen right after tube sampling to minimize the disturbances during transport, storage, and test preparation. Cyclic triaxial test has been carried out to evaluate the liquefaction resistance ratio of undisturbed soil samples. As a result, the liquefaction resistance ratio of samples collected from 8.0~8.8 m and 11.0~11.8 m were almost similar, and these values were approximately 0.04~0.07 larger than values estimated by simplified assessment method using field test results. It is expected that the application of undisturbed sample for the evaluation of liquefaction resistance could contribute to the economical design of geotechnical structures.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.11a
• /
• pp.353-360
• /
• 2000

We developed large diameter sampler (we called KICT type large diameter sampler) to obtain undisturbed clay and sand samples. In-situ test carried out in the In-Chon international airport and Kim-Hae. Also we obtained undisturbed sample with a hydraulic piston sampler in the nearly site and carried out unconfined compression test, consolidation test and triaxial test. The result, unconfined compression strength, secant modules, preconsolidation pressure and undrained shear strength of samples to obtain KICT type large diameter sampler are larger than that of samples to obtain hydraulic piston sampler. But failure strains and volume changes at the consolidation of samples to obtain KICT type large diameter sampler are smaller than that of samples to obtain hydraulic piston sampler

• Journal of the Earthquake Engineering Society of Korea
• /
• v.28 no.1
• /
• pp.67-75
• /
• 2024

In the case of the Pohang earthquake, which had a magnitude of 5.4 in 2017, geotechnical damages such as liquefaction and ground settlement occurred. The need for countermeasures has emerged, and experimental research in the Pohang area has continued. This study collected undisturbed samples from damaged fine-grained soil areas where ground settlement occurred in Pohang. Cyclic tri-axial tests for identifying the dynamic characteristics of soils were performed on the undisturbed samples, and the results were analyzed to determine the cause of ground settlement. As a result of the study, it was determined that in the case of fine-grained soils, ground settlement occurred because the seismic load as an external force was relatively more significant than the shear resistance of the very soft fine-grained soils, rather than due to an increase in excess pore water pressure.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1997.10a
• /
• pp.49-56
• /
• 1997

• Journal of the Korean Geotechnical Society
• /
• v.15 no.5
• /
• pp.125-139
• /
• 1999

It is difficult to evaluate the shear strength of weathered residual soils because of the difficulties of undisturbed sampling. In this study, a sampling device, direct shear box with shoe, was developed in order to get undisturbed samples easily for direct shear tests, and undisturbed samples could be successfully obtained. Through direct shear tests on undisturbed samples, the shear strength was evaluated with the variation of saturated conditions. In order to consider the effect of disturbance on the shear strength, a static compaction device was developed, and then it was found that undisturbed samples show greater shear strengths than the disturbed ones under natural water contents and similar strengths to the ones under soaked conditions. Further, the shear strength evaluated from direct shear tests was compared with the result of triaxial tests on undisturbed samples, and soaked strengths of the former were similar to the latter. As the result of stability analyses on an actual failed slope, it was found that the shear strength can be evaluated reasonably using direct shear box with shoe.

• Journal of the Korean Geotechnical Society
• /
• v.40 no.3
• /
• pp.7-18
• /
• 2024

In this study, slope stability was evaluated in consideration of unsaturated soil behavior to predict landslides. Samples were collected from a landslide site due to heavy rainfall during Typhoon Hinnamnoh. Soil moisture characteristic tests were performed based on the evaporation method using a swelling undisturbed sample and a remolded sample. Based on the hydraulic-mechanical behavior, two-dimensional infiltration and stability analyses were performed. As a result, from the two sample types, it is found that both behaviors exhibited clear differences in the results, and the behavior of the swelling undisturbed sample was able to predict the actual slope failure appropriately.

• Journal of the Korean GEO-environmental Society
• /
• v.6 no.3
• /
• pp.5-15
• /
• 2005

A large diameter sampler that can take undisturbed samples from soft ground was developed by KICT. In order to compare the quality of samples taken by the sampler with those of the traditional piston sampler, a series of laboratory tests were performed. Samples were taken at different sites such as Incheon, Gimhae, Yangsan and Busan. The results showed that the values of unconfined compression strength, secant modulus, pre-consolidation pressure, undrained shear strength, and shear modulus exhibited higher in samples taken by the large scale sampler. Strains at shear failure and volumetric strains were low for the new sampler. It was proved from the comparison that better quality samples could be obtained by the KICT sampler.