• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.113-119
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• 2006

Recently, the ground injection method using water glasses as one of the main resources and the products of these constructions have basic problems in terms of the method of constructions for the permanent foundation reinforcement and stopping leakage of water because they have some serious problems such as durability, compressive strength, injectant eluviation and so forth even though they are still used to stop leakage of water in the temporary structures. The purpose of this study is to demonstrate the strength characteristic and environment friendliness of NDS method by unconfined compressive strenth test, permeability test, length change test, leaching test, and assessment of environmental impact in comparison water glass type material. The test results show that NDS method has significant improvement of strength, permeability, volume change, and leaching. An assessment of environmental impact also demonstrates that the NDS material is environmentally friendly.

• Journal of the Korean GEO-environmental Society
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• v.15 no.3
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• pp.5-13
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• 2014

This paper presents the results of a numerical investigation on applicability of Light-weighted Foam Soils (LWFS) consisted of dredged soils for soft ground improvement. The engineering properties of LWFS were comprehensively investigated based on the previous experimental tests. And three dimensional numerical models which reflect soft ground conditions were adopted to evaluate the applicability of LWFS compared to SCP and DCM. A number of cases were analyzed using a stress-pore pressure coupled model. The results indicated that LWFS method enables to reduce more settlement, lateral flow and heaving than SCP method and enable to reduce more residual settlement than DCM method. Also it was revealed that such effect depends on the properties of LWFS such as unit weight, unconfined compressive strength, deformation modulus and Poisson's ratio.

• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.21-28
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• 2013

This study proposed optimum lime contents for clayey soils consisting of representative clay minerals, Kaolinite and Na-Bentonite, according to optimum lime content method (ASTM C 977-22) by means of ground improvement method of clayey soils. As geotechnical properties, the variations of atterberg limits and unconfined compressive strength were analyzed and Ca-ion and micro-structure along elapsed time were observed for lime-added clayey specimens. The test results show that optimum lime content method provides an appropriate methodology for ground improvement of clayey soils and the variation of $Ca^{2+}$ might be a good index to predict the rate of ground improvement for clayey soils with lime addition.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.4
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• pp.303-310
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• 2000

This study is conducted in order to find more improved solidifying effects than the former converter slag solidification technology. The converter slag is used as a solidifying agent, and the quick lime and the gypsum are used as solidifying aids. Several tests are performed for the purpose of investigating the solidifying effects and the applicability of the solidified sludge as a daily or intermediate landfill cover. The unconfined uniaxial compressive strength, pH and leaching of heavy metal are investigated. In the case of using both quick lime and gypsum as solidifying aids, the compressive strength of specimen has significantly increased that of specimen which used quick lime only. The compressive strength of each specimen cured for 7 days which is mixed with quick lime and gypsum as mixing ratios 7:1, 5:1 and 3:1 are $0.59kg/cm^2$, $1.18kg/cm^2$, and $1.25kg/cm^2$, respectively. The results of all the leaching tests of specimen cured for 7 days show that the concentrations of leachate heavy metals(Cu, Pb, Cd and $Cr^{6+}$) are lower than the Korea toxic waste criteria. The microstructure analysis by SEM shows that needlelike crystals appear as the solidification proceed. The analysis of these crystals by EDS confirms that these main components are Ca. Si etc. Also, XRD analysis shows that the main solidification products are CSH and Ettringite; in addition, $Ca(OH)_2$ CAH are observed. When the added gypsum is used as a solidifying aid, more improved solidifying effects are obtained and the solidified sludge may be appropriately used as a daily or intermediate landfill cover.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.1
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• pp.102-111
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• 1997

Experiments both in laboratory and field were performed to compare and analyze the characteristics of alluvial clay. The alluvial clay was sampled in test site in which large-scaled tests for the part of the site are under process to suggest the rational method for alluvial clay and the criterion for ground settlement monitoring system. The followings were observed through the experiments : 1. Natural water content, plastic limit, and liquid limit of alluvial clay composed of highly fine grains were 40~80%, 10~20%, and 30~55%, respectively. The values of these properties were relatively small at the ground surface, while the values showed maximum at G.L.- l0m and gradually decreased below the level. 2. Shear strength of alluvial clay was proportionally increased to the depth. Unconfined and triaxial compressive strengths were 0.2~0.6kgf/$cm^2$ and 0.1~0.3kgf/$cm^2$, respectively. 3. Compression index and secondary compression index showed maximum values at G.L.-l0m and gradually decreased below the level. The value of consolidation coefficient was relatively large at the ground surface, constant with decreasing the depth, and incresed when G.L. was below -20m. 4. Piezocone test appeared that alluvial clay with N value of 2~4 was uniformly distributed with 20~ 30m thickness from the ground surface, sand seam was nonuniformly distributed, and penetration pore pressure was 0.8 ~ 1 times of the hydrostatic pressure. Undrained shear strength and consolidation coefficient were 0.04 ~ 0.76kgf / $cm^2$ and $2.88{\times} 10{^-4}~1.3{\times} 10{^-2} cm^2/s$ respectively.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.1
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• pp.29-37
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• 1984

This study was made to find several significant relations among various physical and mechanical properties including cone penetration resistance. The alluvial clay samples were taken at the Daebul Reclaimed Tideland in Samhomyeon, Yeongamgun, Jeonranamdo. The results of the study are summarized as follows; 1.Most samples belong to medium or high plastic, inorganic, silty clay(clay contents;32-64%, silt contents; 36-68%, sand contents; 0-3%). The specific gravities range from 2.70 to 2.73, the unit weights from 1.45 to 1. 75g/cm$^3$, the natural moisture contents from 45 to 77%, the liquid limits from 32 to 56%. It is certain that the foundation is weak because the natural moisture contents are much higher than the liquid limits. 2.It is known from the shear tests that the unconfined compression strenghs vary from 0.09 to 0. 38kg/cm2, the cohesions from 0.05 to 0. 21kg/cm2, the internal friction angles from 0 to 3˚. 3.The consolidation tests show that the initial void ratios range from 1.25 to 2.28, the compression indeices from 0.43 to 0.84, the preconsolidation loads from 0.21 to 0.74kg/cm$^2$. 4.Cone penetration resistances are usually less than 5kg/cm$^2$ from ground surface to the depth of about 8m, and from S to l0kg/cm$^2$ in the layer below about 8m to hard layer. 5.The cohesion and cone penetration resistance are in proportion to the depth of soil layer. 6.The correlations between various physical and mechanical properties including cone penetration resistance for the alluvial clay samples are as follows; a) Wn=0.944C+ l2.733 (r=0.829) b) LL=0. 728Cy+6. 991 (r=0. 873) c) PI=0.659Cy-8.168 (r=0.860) d) rt=0. 0077(272-Wn) =2.092-0. 0077Wn (r=0. 859) e) 60=0. 035wn-0 447 (r=0. 893) f) C=0.380qw+0.031 (r=0.816) g) qu=0.0707qc+0.029 (r=0.810) h) C=0.018Z+0.055 (r=O.802) I) qc=0. 415Z+1, 438 (r=0. 943)

• Environmental Engineering Research
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• v.21 no.1
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• pp.15-21
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• 2016

Magnesium potassium phosphate cement (MKPC) is an effective agent for solidification/stabilization (S/S) technology. To further explore the mechanism of the S/S by MKPC, two kinds of Cd including $Cd(NO_3)_2$ solution (L-Cd) and municipal solid waste incineration fly ash (MSWI FA) adsorbed Cd (S-Cd), were used to compare the effects of the form of heavy metal on S/S. The results showed that all the MKPC pastes had a high unconfined compressive strength (UCS) above 11 MPa. For L-Cd pastes, Cd leaching concentration increased with the increase of Cd content, and decreased with the increase of curing time. With the percentage of MSWI FA below 20%, S-Cd pastes exhibited similar Cd leaching concentrations as those of L-Cd pastes, while when the content of MSWI FA come up to 30%, the Cd leaching concentration increased significantly. To meet the standard GB5085.3-2007, the highest addition of S-Cd was 30% MSWI FA (6% Cd contained), with the Cd leaching concentration of 0.817 mg/L. The S/S of L-Cd is mainly due to chemical fixation, and the hydration compound of Cd was $NaCdPO_4$, while the S/S of S-Cd is due to physical encapsulation, which is dependent on the pore/crack size and porosity of the MKPC pastes.

• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.65-71
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• 2005

Recently, difficulties in soft ground improvement that caused by effectiveness of the ground improvement, the durability and environmentally friendliness of the injection material come to the fore. This paper studies the field applicability of the SCM in reinforcement and seepage cutoff of the back of an existing continuous wall. SCM uses double rod which imposes heavy pressure($10-100kgf/cm^2$) to disturbed, cut, discharge, and mix the ground. It is observed that a bulb is formed by using cement paste and environmentally friendly injection materials with minimal alkali leaching. Unconfined compression test and fish poison tests are performed. Test results indicate that the method results in higher durability, less leaching through use of the environmentally friendly injection material, and faster mobilization of the strength. In addition, field tests confirm the formation of the bulb and the seepage cutoff wall.

• Journal of the Korean GEO-environmental Society
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• v.9 no.3
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• pp.29-34
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• 2008

A large diameter sampler was developed to take undisturbed samples from not only soft ground but also sandy and weathered ground. The large diameter sampler which was developed in Korea Institute of Construction Technology(KICT-type large diameter sampler) was manufactured based on the principle of triple core barrel sampling. A specially designed cutting device was used to cut and contain various kinds of samples in the sampler during a sampling and retrieval procedure. By adjusting the stiffness of the spring located at the top of the sampler, the distance between the cutting shoe and auger can be controlled in accordance with the ground condition. In order to investigate the applicability of the developed sampler and compare the quality of the samples taken by the sampler with that by the traditional thin-walled tube sampler, samples were taken at various sites according to the ground condition. And a series of laboratory tests such as the unconfined compress ion test, triaxial compression test, oedometer test, large diameter Rowe cell consolidation test (D: 150 mm) were performed. The test results showed that the samples by the KICT-type large diameter sampler show higher quality than the samples by the thin-walled tube sampler. And the validity and applicability of the developed KICT-type large diameter sampler was confirmed accordingly.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.135-149
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• 2017

The prediction of the actual ultimate capacity of confined concrete columns requires partial confinement utilization under eccentric loading. This is attributed to the reduction in compression zone compared to columns under pure axial compression. Modern codes and standards are introducing the need to perform extreme event analysis under static loads. There has been a number of studies that focused on the analysis and testing of concentric columns. On the other hand, the augmentation of compressive strength due to partial confinement has not been treated before. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength of concrete. Accordingly, the ultimate eccentric confined strength is gradually reduced from the fully confined value $f_{cc}$ (at zero eccentricity) to the unconfined value $f^{\prime}_c$ (at infinite eccentricity) as a function of the ratio of compression area to total area of each eccentricity. This approach is used to implement an adaptive Mander model for analyzing eccentrically loaded columns. Generalization of the 3D moment of area approach is implemented based on proportional loading, fiber model and the secant stiffness approach, in an incremental-iterative numerical procedure to achieve the equilibrium path of $P-{\varepsilon}$ and $M-{\varphi}$ response up to failure. This numerical analysis is adapted to assess the confining effect in rectangular columns confined with conventional lateral steel. This analysis is validated against experimental data found in the literature showing good correlation to the partial confinement model while rendering the full confinement treatment unsafe.