• Journal of the Korean Geosynthetics Society
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• v.17 no.2
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• pp.1-7
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• 2018

The number of construction of roads and railroads in soft ground such as coastal areas and wetlands is getting increased. For this reason cases that soft ground improvement is applied are increasing. In general, many ground improvement methods consider only the working conditions at the time or only economy. But if the working condition and economy are taken into consideration together, the number of applicable construction method gets limited. In such a case, a ground improvement method using both the surface layer portion and the deep layer portion is applied. But the basic research on this is still insufficient in practice. Therefore, in this study the reinforcement effect of geogrid was investigated by carrying out the model test realizing the case in which soft surface ground improvement and depth improvement are simultaneously applied. And it was intened to understand the effect of the thickness of surface layer, the diameter and length of the improvement body on the reinforcement effect of geogrid. The result showed that the effect of the surface layer thickness is greater than the effect of the deep layer diameter. Moreover, when the surface layer is reinforced with a geogrid, the strength of the surface layer part is enhanced and this effect of a geogrid reinforcement caused the reduction of surface settlement.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.157-165
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• 2000

The applicability and performance of HMS-25 as the railroad roadbed materials were evaluated through the model and laboratory tests. The uniaxial compression test of HMS-25, model soil box test, and combined resonant column and torsional shear test were performed for static and dynamic analysis of railroad roadbed. The uniaxial compression test result of HMS-25 shows steady increase in strength due to hardening chemical reaction between HMS-25 and water. The result of model soil box test reveals that railroad roadbed of HMS-25 is better than that of soil in several aspects such as bearing capacity and settlement. The combined resonant column and torsional that shear test result indicates that shear modulus of HMS-25 increases with the power of 0.5 to the confining pressure and that shear modulus increases with the increase of curing period.

• Journal of the Korean Geotechnical Society
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• v.22 no.7
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• pp.37-44
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• 2006

This paper investigates strength characteristics and stress-strain behaviors of geogrid mixing reinforced lightweight soil. The lightweight soil was reinforced with geogrid in order to increase its compressive strength. Test specimens were fabricated by various mixing conditions including cement content, initial water content, air content and geogrid layer and then unconfined compression tests were carried out. From the experimental results, it was found that unconfined compressive strength as well as stress-strain behavior of lightweight soil was strongly influenced by mixing conditions. The more cement content that is added to the mixture, the greater its unconfined compressive strength. However, the more initial water content or the more air foam content, the less its unconfined compressive strength. It was observed that the compressive strength of reinforced lightweight soil increased reinforcing effect by the geogrid for most cases. Stress-strain relation of geogrid mixing reinforced lightweight soil showed a ductile behavior rather than a brittle behavior. In reinforced lightweight soil, secant modulus ($E_{50}$) also increased as its compressive strength increased due to the inclusion of geogrid.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.29-36
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• 2016

Backfill materials of rail abutment were commonly composed with cement treated aggregate, general aggregate and soil. The friction angle of cement treated aggregate increased up to $40^{\circ}$ or more due to strength enhancement. However, $30^{\circ}{\sim}35^{\circ}$ of friction angle was typically applied for in-situ condition. This phenomenon could cause over-designing, therefore, it is essential to determine reasonable material properties of cemented treated aggregate. In this study, a series of CBR tests and circular model tests have been conducted for cement treated aggregate, while changing cement mixing ratio. Based on test results, characteristics of settlement and strength have been analyzed quantitatively. The settlement of cement treated aggregate decreased with the number of cyclic loading and aging period. In addition, The strength increment ratio in CBR test increased up to 13~16 times at 28 days aging.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2C
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• pp.99-108
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• 2006

In this study a series of bench scale test are conducted to increase the undrained shear strength of clayey soils using by Electro-kinetic injection stabilization method. The sodium silicate was injected in anode reservoir and its concentration was changed with 500, 1000, 1500, 2000, 2500mM for configuration of applicability of Electro-kinetic injection stabilization method. Also, the treatment time and electric gradient was changed to acquire the optical influence factors. For increasing the shear strength to maximum values, the calcium chloride and aluminium hydroxide, which concentration was changed with 50, 250, 500, 750, 1000mM, were added at anode reservoir for 5 days after the treatment of sodium silicate in 5 days as the 2nd additives. The test of results in determination of sodium silicate concentration show that the undrained shear strength at each point had a tendency to converge into a constant value when the concentration of sodium silicate came to 1000mM and above. The maximum shear strength increasement was 800% compared with initial value. After a series of test, the electric gradient and treatment time for application of electric fielld were 1V/cm and 6 days. In case of 2nd additives test, the concentration for maximum shear strength is 250mM in all additives and the effects of shear strength improvement was developed approximately 20~30% in comparison to addition of single injection material.

• Journal of the Korean Geosynthetics Society
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• v.22 no.2
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• pp.13-21
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• 2023

Mean sea level has recently been rising due to global warming causing coastal erosion. As Korea is peninsula, the land loss due to coastal erosion is critical. An approach in this study is cementing the coastal area using bacteria, which is called microbially induced carbonate precipitation (MICP). This study tried to see how fresh water and sea water work with MICP as a solvent. Ureolytic activity during the MICP reaction was measured with deionized and sea water. A soil column was prepared to evaluate the strength of MICP-treated sand. Sands were treated by MICP with surface percolation method. As the treatmen t style was different with other conventional methods, several methods were proposed to properly evaluate the MICP-treated sand surface. A micro-scale evaluation was performed to assess the mineral structure treated by different solvents. As results, sea water rendered the ureolytic reaction slower. A needle penetrometer worked well to evaluate the MICP-treated sand surface. This study confirmed the utilization of sea water is feasible as the solvent of MICP.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.221-230
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• 2017

We developed a polymer pouch using PVP that is water soluble in the precedent study. Yet melt viscosity was so low that it was not possible to produce hemispheric type which is essential for mass production, therefore we used another material to make the polymer pouch. It enabled to figure out a water-soluble transition and mechanic physical property of PEG that is newly chosen, and to blend the PEG with LLDPE and TALC followed by result. So, we could implement an evaluating property on blended proportion. It is important to find out a proper blending ratio throughout an experiment since its property is different or varied followed by each proportion as a water soluble character is conflict to a solid character. With the blending technique we were able to produce the polymer pouch enhanced for a tensile force and an impact intensity maintaining a water soluble character. We could identify a ground solidity effect of the polymer pouch as a result of a direct shear test using the product developed.

• Journal of the Korean GEO-environmental Society
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• v.22 no.12
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• pp.59-63
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• 2021

This study presented the characteristics and additive effects of the grout with mixing ratio for developing of high-efficiency grouting technology under high depth conditions. The laboratory investigation were conducted with Portland cement (OPC) and micro cement (S8000-E) including viscosity experiments, particle size analysis experiments, Gel-Time experiments and uniaxial compressive strength experiments. As a result of the viscosity experiment, it was shown that OPC is advantageous in terms of viscosity, but S8000-E is suitable when considering the passage of rock joint intervals through particle size analysis. The Gel-Time experiment shows that it is not that difficult with injection as a grout material even when silica fume (SF) was applied. The strength of the cured material is improved as increase in the content of silica fium (SF). Within the range of the study, the optimal mixing ratio obtained through various experiments is S8000-E, w/c=70%, silica fium (SF)=6%, and 7 days.

• Journal of the Korean Geotechnical Society
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• v.37 no.4
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• pp.39-47
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• 2021

Recently, the enzyme-induced carbonate precipitation (EICP) technique has been considered as one of the alternatives to the cement-based soil reinforcing method. However, the problem with the emission of ammonium ion has not been solved. In this study, an experimental study on the EICP without releasing an environmental contaminant (Ze-EICP) is performed using calcium-exchanged zeolite. The results show that the Ze-EICP using calcium-exchanged zeolite reduced the amount of ammonium ions by 96.96% and precipitated almost the same amount of calcium carbonate, compared to the EICP using calcium chloride. In addition, the Ze-EICP shows higher strength improvement rate than the EICP due to densification of zeolite and cementation of calcium carbonate.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.13-20
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• 2017

In this study, laboratory tests were performed to evaluate for new filling materials (ZA-Soil) for bored pile that were developed using by high calcium ash. As a result of laboratory test, the uniaxial compression strength of 2 types of ZA-Soil are shown 68.0% and 64.6% compared to ordinary portland cement. And it have a suitable flowability and environmental stability. Also, after 28days, uniaxial compression strength of material mixed with soil and high strength filling material (ZA-Soil) for bored pile is 1.10-1.23 times bigger than material mixed with ordinary portland cement.