• Geomechanics and Engineering
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• v.2 no.1
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• pp.19-28
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• 2010

This paper describes the compaction and strength behavior of black cotton soil (BC soil) reinforced with coir fibers. Coir used in this study is processed fiber from the husk of coconuts. BC soil reinforced with coir fiber shows only marginal increase in the strength of soil, inhibiting its use for ground improvement. In order to further increase the strength of the soil-coir fiber combination, optimum percentage of 4% of lime is added. The effect of aspect ratio, percentage fiber on the behavior of the composite soil specimen with curing is isolated and studied. It is found that strength properties of optimum combination of BC soil-lime specimens reinforced with coir fibers is appreciably better than untreated BC soil or BC soil alone with coir fiber. Lime treatment in BC soil improves strength but it imparts brittleness in soil specimen. BC soil treated with 4% lime and reinforced with coir fiber shows ductility behavior before and after failure. An optimum fiber content of 1% (by weight) with aspect ratio of 20 for fiber was recommended for strengthening BC soil.

• Composites Research
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• v.31 no.1
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• pp.23-29
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• 2018

The RFI process can be applied to very thick structures without limiting the resin viscosity. When the proper thickness of the resin film cannot be set, the resin film creates either the non-impregnated section or the excessive resin contents and this leads to the deterioration of mechanical properties. Therefore, this study proposed a method for setting the resin film thickness in the RFI process. The fiber compaction behavior test was proposed by setting the proper resin film thickness and the properties of composites were evaluated through short beam shear strength test, compression test and porosity measurement to verify the proposed method. The evaluation of physical properties of composites was conducted and an appropriate level of resin film thickness was found based on the results of fiber compaction behavior test.

• Geomechanics and Engineering
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• v.12 no.1
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• pp.71-83
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• 2017

Collapsible soil presents a porous unsaturated structure, its sudden settlement after humidification, without supplementary charge, can be of a big nuisance for the foundations and therefore for the constructions built on it. To improve its structure and limit its instability, samples of laboratory reconstituted soil, with different percentages of water contents and compacted at different compaction energies, were treated with glass-fiber. The study of the mechanical behavior was performed by oedometer tests. The microstructure was explored by the Scanning Electron Microscope (SEM). The results obtained show clearly the efficiency of the treatment with glass fiber on reducing the collapsibility of such soil.

• Earthquakes and Structures
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• v.20 no.4
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• pp.365-375
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• 2021

Rammed earth (RE) buildings have existed all over the world for thousands of years, and have gained increasing attention because of its sustainable advantages, however, the shrinkage cracks reduce its bearing capacity and seriously affect its durability and applicability. In this study, the shrinkage cracks test was carried out to investigate the effects of initial water content, proportion of sand and gravel, compaction degree, thickness and the additives (polypropylene fiber, cement and sodium silicate) of shrinkage cracks in RE buildings, ten groups of RE samples were prepared and dried outdoors to crack. Four quantitative parameters of geometrical structure of crack patterns were used to evaluate the development of cracks. The results show that the specimens cracking behavior and the geometrical structure of crack patterns are significantly influenced by these considered factors. The formation of crack can be accelerated with the increase of initial water content and thickness of specimen, while restricted with the increase of the compaction degree and the proportion of sand and gravel. Moreover, the addition of 1% polypropylene fiber, 10% cement and 0.5 volume ratio sodium silicate can significantly restrain the form and development of cracks. In RE construction, these factors should be considered comprehensively to prevent the harm caused by shrinkage cracks. Further works should be carried out to obtain the optimum dosage of the additives, which can benefit the construction of RE buildings in future.

• Geomechanics and Engineering
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• v.10 no.2
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• pp.155-174
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• 2016

A total of 104 laboratory model tests on a square footing subjected to eccentrically inclined loads supported by sand reinforced with randomly distributed polypropylene fibers were conducted in order to compare the results with those obtained from unreinforced sand and with each other. For conducting the model tests, uniform sand was compacted in a test box at one particular relative density of compaction. The effect of percentage of reinforcement used, thickness of the reinforced layer, angle of inclination of load to vertical and eccentricity of load applied on various prominent factors such as ultimate load, vertical settlement, horizontal deformation and tilt were investigated. An improvement in ultimate load, vertical settlement, horizontal deformation and tilt of foundation was observed with an increase in the percentage of fibers used and thickness of reinforced sand layer under different inclinations and eccentricities of load. A statistical model using non-linear regression analysis based on present experimental data for predicting the vertical settlement ($s_p$), horizontal deformation ($hd_p$) and tilt ($t_p$) of square footing on reinforced sand at any load applied was done where the dependent variable was predicted settlement ($s_p$), horizontal deformation ($hd_p$) and tilt ($t_p$) respectively.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.250-253
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• 2004

Emphasis has been placed on thin plate fabrication of plain woven carbon fabric reinforced Al matrix composites using liquid pressing process. The composite has potential applications for PDP rear plate. The process is to use the low pressure for infiltration of Al melt into plain woven carbon fabric as the Al melt is pressurized directly. The minimum pressure required for the infiltration was calculated from force balance equation, permeability measurements and compaction behavior of carbon fiber. Also, the melting temperature and the holding time have been optimized. In order to measure coefficient of thermal expansion (CTE) of the composites, the thermal strain measurement using strain gage was performed and the thermal conductivity of the composites was measured using laser flash method. The constituent materials of the composite are PAN type carbon fibers as reinforcements and 6061 Al alloys as matrices.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.133-144
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• 2009

Incheon Bridge, 18.4 km long sea-crossing bridge, will be opened to the traffic in October 2009 and this will be the new landmark of the gearing up north-east Asia as well as the largest & longest bridge of Korea. Incheon Bridge is the integrated set of several special featured bridges including a magnificent cable-stayed girder bridge which has a main span of 800 m width to cross the navigation channel in and out of the Port of Incheon. Incheon Bridge is making an epoch of long-span bridge designs thanks to the fully application of the AASHTO LRFD (load & resistance factor design) to both the superstructures and the substructures. A state-of-the-art of the geotechnologies which were applied to the Incheon Bridge construction project is introduced. The most Large-diameter drilled shafts were penetrated into the bedrock to support the colossal superstructures. The bearing capacity and deformational characteristics of the foundations were verified through the world's largest static pile load test. 8 full-scale pilot piles were tested in both offshore site and onshore area prior to the commencement of constructions. Compressible load beyond 30,000 tonf pressed a single 3 m diameter foundation pile by means of bi-directional loading method including the Osterberg cell techniques. Detailed site investigation to characterize the subsurface properties had been carried out. Geotextile tubes, tied sheet pile walls, and trestles were utilized to overcome the very large tidal difference between ebb and flow at the foreshore site. 44 circular-cell type dolphins surround the piers near the navigation channel to protect the bridge against the collision with aberrant vessels. Each dolphin structure consists of the flat sheet piled wall and infilled aggregates to absorb the collision impact. Geo-centrifugal tests were performed to evaluate the behavior of the dolphin in the seabed and to verify the numerical model for the design. Rip-rap embankments on the seabed are expected to prevent the scouring of the foundation. Prefabricated vertical drains, sand compaction piles, deep cement mixings, horizontal natural-fiber drains, and other subsidiary methods were used to improve the soft ground for the site of abutments, toll plazas, and access roads. Light-weight backfill using EPS blocks helps to reduce the earth pressure behind the abutment on the soft ground. Some kinds of reinforced earth like as MSE using geosynthetics were utilized for the ring wall of the abutment. Soil steel bridges made of corrugated steel plates and engineered backfills were constructed for the open-cut tunnel and the culvert. Diverse experiences of advanced designs and constructions from the Incheon Bridge project have been propagated by relevant engineers and it is strongly expected that significant achievements in geotechnical engineering through this project will contribute to the national development of the longspan bridge technologies remarkably.