• Korean Journal of Soil Science and Fertilizer
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• v.38 no.4
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• pp.188-193
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• 2005

Pantoea agglomerans immobilized in alginate solubilized four different rock phosphates efficiently under in vitro conditions. The solubilization pattern differed according to the rock phosphate source, where maximum solubilization of Morocco and Tunisia rock phosphates (215.6 and $186.1mg\;P\;L^{-1}$) on 6 days, Israel rock phosphate ($60.98mg\;P\;L^{-1}$) and tricalcium phosphate ($132.3mg\;P\;L^{-1}$) on 10 days and China rock phosphate ($48.8mg\;P\;L^{-1}$) on 12 days after inoculation was observed. The shelf life of the immobilized bacteria immobilized beads stored in two different temperatures was studied for six months. Beads stored at both room temperature as well as cold storage ($4^{\circ}C$) were found equally good in supporting the bacterial population as well as phosphate solubilizing activity. P. agglomerans immobilized in alginate might be exploited for large scale biosolubilization of rock phosphates intended for fertilizer use.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.133-145
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• 2020

Soil in mine waste-rock fields, and at the pithead, sediments and farmlands around an abandoned mine in the Chungcheong Province of South Korea were investigated to assess the distribution of metallic elements and to understand the scope of the pollution. Reddening was observed from the mine up to a distance of 61 m. Losses of waste rock around the mine were assessed over a section of 1800 ㎥. Yellowish precipitates on the bottom of a stream were identified as ferrihydrite and goethite. For anions, a mean sulfate ion level over 773.6 mg/L was found during August in the river water samples. Mine drainage at the site was shown to have a pH of 4.9 and a sulfate concentration of 1557.8 mg/L during the August rainy season. A possible cause of the metallic element contamination in the mine is waste-rock loss, because mine waste-rock is located on the slope in this area. In conclusion, the total soil area to be treated, based on the amount that exceeded the recommended Korean soil pollution levels, was assessed to be 10,297 ㎡.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.147-155
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• 2010

A prediction model of resilient modulus($E_R$) was developed for recycled crushed-rock-soil mixtures. The evaluation of $E_R$, using the "orthodox" repeated loading tri-axial test, is not feasible for such a large-size gravelly material. An alternative method was proposed hereby using the subtle different modulus called nonlinear dynamic modulus. The prediction model was developed by utilizing in-situ measured shear modulus($G_{max}$) and its reduction curves of modeled materials using the large free-free resonant column test. A pilot evaluation of the model parameters was carried out for recycled crushed-rock-soil-mixture at a highway construction site near Gimcheon, Korea. The values of the model parameters($A_E,\;n_E,\;{\varepsilon}_r\;and\;{\alpha}$) were proposed as 9618, 0.47, 0.0135, and 0.8, respectively.

• Journal of the Korean Geotechnical Society
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• v.39 no.11
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• pp.23-31
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• 2023

The escalating settlements observed in concrete slab tracks pose a significant challenge in Korea, raising concerns about their adverse impact on the safe operation of high-speed railways and the substantial costs involved in restoration. A primary contributor to these settlements is identified as the utilization of rock materials sourced from tunnel construction, incorporated into the lower subgrade without the requisite soil mixing to achieve an appropriate particle size distribution. This study employs numerical analysis to evaluate the efficacy of partial reinforcement in reducing settlements in rock-filled lower subgrades. Column-shaped reinforcement areas strategically positioned at regular intervals in the lower subgrade induce soil arching in the upper subgrade, leading to a concentration of soil loads on the reinforced areas and consequent settlement reduction. The analysis employs finite element methods to investigate the influence of the size, stiffness, and spacing of the reinforced areas on settlement reduction in the lower subgrade. The numerical results guide the formulation of an optimal design approach, proposing a method to determine the minimum spacing required for reinforcements to effectively limit settlements within acceptable bounds. This research contributes valuable insights into addressing the challenges associated with settlement in concrete slab tracks, offering a basis for informed decision-making in railway infrastructure management.

• Journal of the Korean Geotechnical Society
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• v.26 no.6
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• pp.29-38
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• 2010

Micro-piles have been used to increase the bearing capacity or to restrain settlement of existing shallow foundation. Recently, micro-piles are used to support the shallow foundation, to stabilize the slope and to resist the sliding of retaining wall. Using the micro-piles in geotechnical engineering, some investigators have studied the effective installing method by model test or field test. But most of previous studies are chiefly focused on the micro-piles in sand or clay layer. If a rock layer exists in soil, the installing length of micro-piles may be determined by the depth of rock layer. In this case, the stiffness of pile may be changed by the installing length of pile, and so the installing method has to be altered by the changed stiffness of pile. Model tests have been conducted to study the installation method of micro-pile in soil with rock layer. As a result, when the ratio of length of pile is below 50 ($L/d{\leq}50$), installing of micro-piles in vertical position is effective regardless of the depth of rock layer. If the depth of rock layer is deeper than soil failure zone and the ratio of the length of pile exceeds 50 (L/d>50), installing of the micro-piles in sloped position is effective.

• Journal of the Korean Geotechnical Society
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• v.38 no.6
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• pp.29-39
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• 2022

This study investigates the behavior of a circular vertical shaft wall in the absence and presence of a groundwater table. The effects of wall deflection, backfill settlement, and earth pressure distribution around the circular vertical shaft caused by sequential excavations were quantified. The vertical shaft was numerically simulated for different excavation depths of the bearing layer (weathered soil, weathered rock, soft rock) and transient and steady-state flows in the absence of a groundwater table. The backfill settlements and influential area were much larger under transient flow conditions than in steady-state flow. On the contrary, the horizontal wall deflection was much larger in steady state than in the transient state. Moreover, less settlement was induced as the excavation depth increased from weathered soil to weathered rock to the soft rock layer. Finally, the horizontal stresses under steady- and transient-state flow conditions were found to exceed Rankine's earth pressure. This effect was stronger in the deeper rock layers than in the shallow soil layers.

• Korean Journal of Soil Science and Fertilizer
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• v.6 no.4
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• pp.253-255
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• 1973

Microscopic method was compared with X-ray diflraction analysis for the identification of rockforming minerals using 11 main rock samples in Korea. 1. There was no difference between X-ray diffraction analysis and microscopic one in major minerals, but some accessary minerals. 2. The rock-forming minerals of main rocks presented in this study occured almost in crystalline state so that they could be easily identified by X-ray analysis alone.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.89-92
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• 2001

This study aims at investigating the relationship between dispersion coefficient ratio to molecular diffusion coefficient (D$_{l}$ /D$_{m}$) and Peclet number (Pe) for multi-solute system in non-Darcian flow regime. Existing understanding on solute dispersion is primarily derived from one-solute system in Darcian flow regime. We found that solute dispersion in rock fractures can be characterized by the mechanism of both macrodispersion and Taylor dispersion, even for non-Darcian f]ow domain. For the Darcian flow regime even different solutes lead to the same D$_{l}$ /D$_{m}$ at same Pe. However, as the flow becomes non-Darcian, solute with a higher molecular diffusion coefficient result in higher D$_{l}$ /D$_{m}$ at tile same Pe than that with a lower diffusion coefficient.cient.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.505-510
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• 2007

Concrete track will be constructed in Gyungbu High Speed Railway II(GHSR II) stage construction site from Daegu to Busan. Concrete track is supported by substructure consisting of the original ground and embankment and does not allow the settlement of track because of its structural type. The embankment is composed of rock and soil mixture and settlement is feasible. So management of settlement of embankment is key point in successful construction of the concrete track. Compaction management of mixed fill materials is important in minimizing the settlement of embankment. In this study, in order to assess the compaction characteristics of mixed fill materials, large laboratory compaction tests were conducted. Mixed fill materials were obtained from two construction sites in GHSR II construction site. Modeled mixed fill materials having different rock type, fine content, maximum particle diameter, and moisture contents were prepared. From the test results, compaction characteristics of mixed fill materials were analysed.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.373-376
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• 2004

To investigate the vertical petrological and hydrological characteristics of fractured rock, geophysical and chemical logging were executed at 5 boreholes installed in the study area. The geophysical and hydrochemical logging data were analysed by using principal components analysis (PCA). Three main variables from PCA explained 86.4% of total variance of geophysical log data. The PCA results showed that PCl is closely related to groundwater properties and PC2 and PC3 are influenced by rock and fracture properties. Hydrochemical analysis indicated the presence of highly fractrued zone at the depth of 60m.