• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.59-64
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• 2005

Although high pressure discharge method is widely used for improving soft ground, it has various problems including lack of strength increase and the possibility of water pollution and soil contamination. MJM(Morta Jet Method) uses sand in addition to cement as the injection material. MJM uses triple rods with a built-in nozzle that allows easier discharge of the slime, resulting in higher replacement area ratio and more uniform formation of pillar hydrates, and thus results in significant increase in strength. MJM is expected to perform especially well as piles in marine clays. This study investigates the field applicability of the MJM through extensive laboratory and field tests.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1712-1716
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• 2008

Performance of ground improvement project using prefabricated vertical drains of condition, in which approximately 10m dredged fill overlies original soft foundation layer in the coastal area has been conducted. From field monitoring results, excessive ground settlement compared to predicted settlement in design stage developed during the following one year. In order to predict the final consolidation behavior, recalculation of consolidation settlements and back analysis using observed settlements were conducted. Field monitoring results of surface settlements were evaluated, and then corrected because large shear deformation was occurred by construction events in the early stages of consolidation. To predict the consolidation behavior, material functions and in-situ conditions from laboratory consolidation test were re-analyzed. Using these results, height of additional embankment is estimated to satisfy residual settlement limit and maintain an adequate ground elevation. The recalculated time-settlement curve has been compared to field monitoring results after additional surcharge was applied.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.87-94
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• 1999

Sand drain as a vertical drainage is widely used in soft ground improvement. Recently, sand, the principal source of sand drain, is running out. A laboratory model test was carried out to utilize gravel as a substitute for sand. Though which the characteristics of gravel are compared to those of sand for engineering purpose. Two cylindrical containers for the model test were filled with marine clayey soil from the west coast of Korea with a column in the center, one with sand, the other with gravel. Vibrating wire type piezometers were installed at the distance of 1.0D, 1.5D and 2.0D from the center of the column. D is the diameter of the column. The transient process of pore water pressure with loading and the characteristics of consolidation were studied with the data gained from the measuring instrument place on the surface of the container. The parameter study was performed for the marine clayey soil before and after the test in order to check the effectiveness of the improvement. The clogging effect was checked at various depth in gravel column after the test. According to the test, the settlement was found to be smaller in gravel drain than in sand drain. The increase in bearing capacity by gravel pile explains the result. The clogging effect was not found in gravel column. As a result, it is assumed that gravel is relatively acceptable as a drainage material.

• Journal of the Korean GEO-environmental Society
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• v.13 no.10
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• pp.77-83
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• 2012

Recently, excavations using propped walls were popularized in downtown due to reduced settlement of nearby structures. These excavations is induced strain to propped walls or settlement in near ground. In this study, the ground reinforcing effect was proven using NDS, which is an inorganic injection material. Injection tests were performed to compute optimum injection pressure and volume. Next, calibration chamber tests were performed by using computed injection pressure and volume, and wall behaviour was examined for overburden pressures of 50kPa and 150kPa. Ground reinforcing effect was shown when the material behind the propped wall was grouted. From test results, optimum injection pressure was 350kPa and the optimum volume was 10L considering economics. Calibration chamber test results show that after the material was grouted, the maximum settlement was reduced to 19% of the non-grouted condition. For overburden pressures of 50kPa and 150kPa behind the wall, the settlement of the wall increased by 58% and 57% when compared to the case of no overburden pressure.

• International Journal of Aerospace System Engineering
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• v.6 no.1
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• pp.1-7
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• 2019

In the present study, structural safety and stability on the main wing and tail planes of the 1.2 ton WIG(Wing in Ground Effect) flight vehicle, which will be a high speed maritime transportation system for the next generation, was performed. The carbon-epoxy composite material was used in design of wing structure. The skin-spar with skin-stressed structural type was adopted for improvement of lightness and structural stability. As a design procedure for this study, the design load was estimated with maximum flight load. From static strength analysis results using finite element method of the commercial codes. From the stress analysis results of the main wing, it was confirmed that the upper skin structure between the second rib and the third rib was unstable for the buckling load. Therefore in order to solve this problem, three stiffeners at the buckled region were added. After design modification, even though the weight of the wing was a little bit heavier than the target weight, the structural safety and stability was satisfied for design requirements.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.51-61
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• 2016

New building methods are needed to aid increased inner-city redevelopment and industrial construction. A particular area of improvement is the efficient use of cut slopes, with the minimization of associated problems. A retaining wall of precast panels can resist the horizontal earth pressure by increasing the shear strength of the ground and reinforcing it through contact with the panels. Precast panels allow quick construction and avoid the problem of concrete deterioration. Other problems to be solved include the digging of borrow pits, the disposal of material cut from the slope, and degradation of the landscape caused by the exposed concrete retaining wall.This study suggest the methods of improvement of an existing precast panel wall system by changing the appearance of the panels to that of natural rock and improving the process of adhering the panel to a vertical slope. The panels were tested in the laboratory and in the field. The laboratory test verified their specific strength and behavior, and the field test assessed the panels' ground adherence at a vertical cutting. Reinforcement of the cutting slope was also measured and compared with the results of 3D numerical analysis. The results of laboratory test, identified that the shear bar increase the punching resistance of panel. And as a results of test construction, identified the construct ability and field applicability of the panel wall system adhered to in-situ ground. In addition to that, extended measurement and numerical analysis, identified the long-term stability of panel wall system adhered to in-situ ground.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.5-15
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• 2008

The purpose of this study is to examine the validity of recycled aggregates (RAs) as a substitute for Sand-Mat material for soft ground improvement in the housing site development. To evaluate the possibility of RAs as a substitute for sand mat material, first of all, the criteria and regulations related with the quality of lateral drain layer were collected and checked. Secondly, both of the properties of RAs were compared with the properties of natural sand for the lateral drain layer. The material properties related to coefficient of permeability, pressure at-rest state and so on satisfied most standards. On the basis of the test results, RAs were used to the construction site as lateral drain layer. Accordingly, if the quality of RAs can be managed well, the application of these RAs as lateral drain layer to replace natural sand was highly effective. Also, based on cost analysis of two materials, RAs are proved to be very competitive.

• Geomechanics and Engineering
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• v.4 no.3
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• pp.191-208
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• 2012

Due to rapid industrialisation, large scale infrastructure development is taking place worldwide. This includes railways, high speed highways, elevated roads etc. To meet the demands of society and industry, many innovative techniques and materials are being developed. In developed nations like USA, Japan etc. for railways applications, new material like geocells, geogrids are being used successfully to enable fast movement of vehicles. The present research work was aimed to develop design methodologies for improvement of grounds subjected to cyclic loads caused by moving vehicles on roads, rail tracks etc. Deformation behavior of ballast under static and cyclic load tests was studied based on square footing test. The paper presents a study of the effect of geo-synthetic reinforcement on the (cumulative) plastic settlement, of point loaded square footing on a thick layer of granular base overlying different compressible bases. The research findings showed that inclusion of geo-synthetics significantly improves the performance of ballasted tracks and reduces the foundation area. If the area is kept same, higher speed trains can be allowed to pass through the same track with insertion of geosynthetics. Similarly, area of machine foundation may also be reduced where geosynthetics is provided in foundation. The model tests results have been validated by numerical modeling, using $FLAC^{3D}$.

• Composites Research
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• v.36 no.4
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• pp.264-269
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• 2023

Spent coffee grounds (SCG) are a ubiquitous byproduct of coffee consumption, representing a significant waste management challenge, as well as an untapped resource for economic development and sustainability. Improper disposal of SCG can result in environmental problems such as methane emissions and leachate production. This study aims to investigate the physicochemical properties of SCG and their potential as a reinforcement material in polypropylene (PP) to fabricate an eco-friendly composite via extrusion and injection molding, with SCG filler ratios ranging from 5-20%. To evaluate the effect of SCG on the morphological and mechanical properties of the bio- composite, thermogravimetric analysis, SEM, tensile, flexural, and impact tests were conducted. The results demonstrated that the addition of SCG lead to a slight increase in brittleness of the composite but did not significantly affect its mechanical properties. Impressively, the presence of a significant organic component in SCG contributed to the enhanced thermal performance of PP/SCG composites. This improvement was evident in terms of increased thermal stability, delayed onset of degradation, and higher maximum degradation temperature as compared to pure PP. These findings suggest that SCG has potential as a filler material for PP composites, with the ability to enhance the material's properties without compromising overall performance.

• Journal of the Korean Geotechnical Society
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• v.24 no.9
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• pp.33-40
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• 2008

This paper describes the performance of ground improvement project using prefabricated vertical drains of condition, in which approximately 10m dredged fill overlies original soft foundation layer in the coastal area composed of soft marine clay with high water content and high compressibility. From field monitoring results, excessive ground settlement compared with predicted settlement in design stage developed during the following one year. In order to predict the final consolidation behavior, recalculation of consolidation settlements and back analysis using observed settlements were conducted. Field monitoring results of surface settlements were evaluated, and then corrected because large shear deformation occurred by construction events in the early stages of consolidation. To predict the consolidation behavior, material functions and in-situ conditions from laboratory consolidation test were re-analyzed. Using these results, height of additional embankment is estimated to satisfy residual settlement limit and maintain an adequate ground elevation. The recalculated time-settlement curve has been compared with field monitoring results after additional surcharge was applied. It might be used for verification of recalculated results.