• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.10
• /
• pp.393-405
• /
• 2020

Various geotechnical information is required to evaluate the stability of the ground and a foundation once liquefaction occurs due to earthquakes, such as the soil strength and groundwater level. The results of the Standard Penetration Test (SPT) conducted in Korea are registered in the National Geotechnical Information Portal System. If geotechnical information for a non-drilled area is needed, geostatistics can be applied. This paper is about the feasibility of obtaining ground information by the Empirical Bayesian Kriging (EBK) method and the Inverse Distance Weighting Method (IDWM). Esri's ArcGIS Pro program was used to estimate these techniques. The soil strength parameter of the drilling area and the level of groundwater obtained from the standard penetration test were cross-validated with the results of the analysis technique. In addition, Multichannel Analysis of Surface Waves (MASW) was conducted to verify the techniques used in the analysis. The Buk-gu area of Pohang was divided into 1.0 km×1.0 km and 110 zones. The cross-validation for the SPT N value and groundwater level through EBK and IDWM showed that both techniques were suitable. MASW presented an approximate section area, making it difficult to clearly grasp the distribution pattern and groundwater level of the SPT N value.

• Journal of the Korean GEO-environmental Society
• /
• v.7 no.6
• /
• pp.121-131
• /
• 2006

This study is performed to examine the ground reinforcement effect and the environmental impact of LW injection, which is widely used during the excavation of high-rise apartment buildings. In addition, it proved that by conducting field exploration and laboratory test the engineering ground reinforcement effect of LW injection in the ground has low coefficient of permeability. The environmentally friendly aspect was evaluated through an assessment of environmental impact. The results of laboratory test shows that LW coagulating material with SC type soil structure has significant improvement of uniaxial compressive strength, increasing by three times and the shear strength increasing by twice, coefficient of permeability decreasing six to seven times. And the result of environmental impact tests show that from 6 hour after where the pH increases until 7.96 to initially it diminished, it started and to 80 hour after it recovered a pH 7.25 initially with 7.30. The chemical composition analysis test result that unpolluted water and polluted water hydrogen ion concentration (pH) show that the unpolluted water pH 7.36, polluted water pH 7.85, which is inside the Ministry of Environment standard of drinking water (the pH 5.8~8.5). The assessment of environmental impact and chemical analysis test also demonstrate that the LW coagulating material is environmentally friendly. In the $Cr^{6+}$ and the salinity detection test, it was proven that the salinity is slight and the $Cr^{6+}$ is not detected.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.2
• /
• pp.19-32
• /
• 2018

During the process of gas hydrate extraction in the deep seabed, fine diatom particle migration occurs, which causes the seabed slope failure and the productivity deterioration of the gas hydrate. Therefore, a study related with the changes of the ground characteristics due to the fine particle migration is required. The objective of this study is to investigate the change of hydraulic properties of sand due to the migration of fine diatom particle in sandy soils. In order to simulate the sediments of the Ulleung basin gas hydrate in the East Sea, fifteen sand-diatom mixtures that have different diatom volume fractions (DVF) are prepared. During the falling head permeability tests, the coefficients of permeability are measured according to the DVF. In addition, for the simulation of the fine diatom particle migration, constant head permeability tests are conducted by applying the hydraulic pressures of 3 kPa, 6kPa, and 9 kPa on a specimen composed of two layers: a specimen with 50% DVF in upper layer and a specimen with 0% DVF in lower layer. Furthermore, the coefficient of permeability and the electrical resistivity of the migration zone are measured during the constant head permeability test. The falling head permeability tests show that the coefficient of permeability decreases as the DVF of the specimen increases. In addition, the gradient of the coefficient of permeability curve decreases in the DVF range of 10%~50% compared with that of 0%~10%, and increases above 50% in DVF. The result of constant head permeability tests shows that the coefficient of permeability decreases and electrical resistivity increases in the migration zone due to the fine diatom particle migration. This study demonstrates that fine diatom particle migration reduces the permeability of the soils and the behavior of the migration zone due to the fine diatom particle migration may be estimated based on the reversal relationship between the coefficient of permeability and the electrical resistivity.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.18 no.3
• /
• pp.305-318
• /
• 2016

This study is to evaluate the uncertainty of the soil parameters associated with the Gap parameter during shield TBM tunnel excavation of ${\bigcirc}{\bigcirc}$ International Airport Terminal 2 connecting railway construction basic design. And This study is to evaluate the adequacy of the shield TBM design by performing a reliability analysis of the Surface settlement. In addition, By analyzing the reliability indices of the design constants and Sensitivity probability of failure to be used in designing an integer parameter Gap, and By evaluating the design constants of a great influence on the surface subsidence, it was to provide a basis for carrying out an optimum design.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.7
• /
• pp.57-63
• /
• 2010

The necessity of effective and economical improvement for soft ground is required more and more as mountains form 70% of country. The soft ground improvement methods for ocean development are sand compaction pile method, displacement method are applied to the soft ground improvement from ocean development pre-loading method, air pressure method, well point method, pack drain method, quicklime pile method etc. Among them, the sand compaction pile method, has many problems such as the economical problem on importing materials due to the lack of sand and destroying the nature while collecting sand. To replace the sand with other alternative materials, a study on the bottom ash compaction pile method because the bottom ash has the similar engineering properties with sand. Therefore, in this study, after compose the complex soil with a replacement rate of 10~80% and a large direct shear test, shear test, consolidation test with replacement rates of bottom ash are performed to estimate whether its shear and consolidation characteristics are suitable for the alternative material of compaction pile method. As a result of test, Shear Strength Parameters tend to be increased in accordance with the increase of replacement ratio of bottom compaction pile, and Settlement Reduction Factor and $t_{90}$ tend to be decreased.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.4
• /
• pp.295-307
• /
• 2002

In the Nakdong River plain a very thick clayey soils are covered widely. Since the early 1990's, some huge reclamation projects have been performed for the development of industrial and residential complexes and so on. Despite a large number of soil investigations have been carried out for the projects, the geotechnical properties have never been elucidated well, so that the settlements of the ground due to the mischaracterized properties were greatly underestimated. Therefore, it has been needed to evaluate definitely the characteristics of the clayey soils, particularly for the compressibility characteristics to help understand the settlement behavior. For the compressibility characteristics of the Pusan clays, physical index and consolidation tests were conducted on the reconstituted and undisturbed samples. Using the result of physical index, the Pusan clays could be divided into two different units, which have different depositional environments. According to the concepts of Burland (1990) and Nagaraj et. al. (1990), the intrinsic state line and field compression curve of the Pusan clays could be established. It could be found from their concepts that the Pusan clays are under the cemented and young normally consolidated state and largely consisted of two units. The cementation of the clays was as well identified by compression index ratio (Tsuchida et. al.,1991) and sensitivity (Leroueil et. al.,1983).

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.1
• /
• pp.56-62
• /
• 2018

In this study, an artificially formed Gap graded soil, designed to increase its shear strength, was analyzed to determine the strength parameters through direct shear tests. Uniform and fine grain size samples were compared to the Gap graded soil to investigate the increase in the shear strength. Plate loading tests were conducted using 13mm and 19mm aggregates to confirm the reproducibility of the strength enhanced samples for site application. This test confirmed that the particle size ratio and the internal friction angle are correlated to the shear strength, and the shear resistance angle significantly increased in the specific particle size ratio range. The calculation of the ultimate bearing capacity by the plate load test demonstrated that the grain size adjustment method greatly influences the strength increase rate. Therefore, the findings were verified and it was confirmed that a high shear strength is achievable despite the existence of a poor particle size distribution.

• Tunnel and Underground Space
• /
• v.16 no.6 s.65
• /
• pp.506-525
• /
• 2006

For the design of large scale rock slope which has complex formations and geological structures, generally, insufficiency of geotechnical investigations and laboratory tests are the main factors of slope failures doling construction. In such case, remedial measures to stabilize slope should be selected and applied through reliable investigations and analysis considering the geotechnical characteristics. The rock slope of this study, one of the largest cut slopes in Korea with a length of 520.0 m and maximum height of 122.0 m consists of metasedimentary rocks. And a case study on the causes of large-scale rock slope failure was carried out by analysis of landslides history and site investigations during construction. When the slope with the original design slope of 0.7: 1.0 (H:V) was partially constructed, the slope failure was occurred due to the factors such as poor conditions of rocks (weathered zone, coaly shale and fault shear zone), various discontinuities (joints, foliations and faults), severe rain storm and so on. The types of failures were rockfall, circular failure, wedge failure and the combination of these types. So, the design of slope was changed three times to ensure long-term slope stability. This paper is intended to be a useful reference for analyzing and estimating the stability of rock slopes whose site conditions are similar to those of this study site such as geological structures and geotechnical properties.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.4
• /
• pp.319-324
• /
• 2016

Soils with various particle sizes generally show good shear strength. Some soils have a relatively strong resistance to shear failure in spite of narrow particle distribution, such as gap grading. Based on this example, it can be inferred that appropriate arrangements of particle size in soils might result in an increase in shear strength. This study investigates the strength variation of soils with respect to the particle size distribution. Gap, well, and uniform graded soils were prepared with a desired ratio, and a wide range of direct shear tests were done using the prepared samples. The test results show that there is a strong relationship between the particle size ratio and internal frictional angle. Gap graded soil has a greater frictional angle than a well-graded sample, even when specimens have the same maximum particle size, which is also the case for the uniform grade specimen. The results have potential for developing a methodology for stronger soils through a simple manipulation of particle size distribution.

• Journal of the Korean GEO-environmental Society
• /
• v.10 no.6
• /
• pp.19-25
• /
• 2009

The current study developed light-weighted mixed soil that can solve problems related with soft soil such as ground subsidence, sliding and lateral displacement of ground. By reducing weight of reclaimed soil through mixing phosphogypsum and recycled EPS beads with the weathered granite soil. A series of geotechnical laboratory tests including physical index test, compaction test, CBR test, and direct shear test were performed and engineering properties were reviewed in order to assess applicability of the light-weighted mixed soil for roads and abutment and various back-filling materials at the reclamation area. Based on the laboratory test results, it was found that the maximum dry unit weight of the light-weighted soil ranges $14.32{\sim}15.79kN/m^3$ and the optimum water content ranges 21.91~24.23%, which means there is 11~19.3% weight decrease effect when comparing with general weathered granite soil. Also it was found that the corrected CBR value ranges 10.4~18.4% satisfying the domestic regulations on road subgrade and back-filling material. In addition, as for shear strength parameter, cohesion ranges 10.79~18.64 kPa and internal frictional angle ranges $35.4{\sim}37.2^{\circ}$, which are similar with those of general construction soil and back-filling material used in Korea. So it can be concluded that light-weighted mixed soil with phosphogypsum can be used effectively for soft reclamation ground as actual filling material and back-filling material. From the current study, it was found that light-weighted mixed soil with phosphogypsum has not only weight reduction effect, but also has no special problems in shear strength and bearing capacity. Therefore, it is expected that phosphogypsum can be recycled in bulk as road subgrade and back-filling material at the reclamation area.