• Journal of the Korean Geotechnical Society
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• v.27 no.2
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• pp.43-52
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• 2011

The characteristics of shear zone in granular soils largely affect the stability of geo-structures. The goal of this study is to evaluate shear zone in a direct shear test using shear wave, electrical resistivity, and cone tip resistance. Bender elements and electrical resistivity probe are embedded into the wall of a direct shear box made of transparent acrylic material to estimate the shear wave velocities and the electrical resistivity at shear and non-shear zones. At the point of peak and residual strength, micro cone penetration test which can be available to measure tip resistance has been performed. Experimental results show that the shear wave velocities at upper shear zone increase during shearing while the values remain constant at bottom and lower shear zone. Also, resistivities at lower shear zone depend on relative density while resistivities at bottom remain constant. The results of cone penetration test demonstrate the correlation of the cone tip resistance and small strain shear modulus at shear zone. This study suggests that the application of the modified direct shear box including shear wave, electrical resistivity and the micro cone tip resistance may become effective tools for analyzing the characteristics of a shear zone.

• Steel and Composite Structures
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• v.18 no.2
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• pp.467-480
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• 2015

The steel-concrete composite decks have high fatigue durability and deformability in comparison with ordinary RC slabs. Withal, the steel-concrete composite deck is mostly heavier than the RC slabs. We have proposed herein a new type of steel-concrete composite deck which is lighter than the typical steel-concrete composite decks. This can be achieved by arranging hollow sectional members as shear connectors, namely, half-pipe or channel shear connectors. The present study aims to experimentally investigate mechanical characteristics of the half-pipe shear connectors under the direct shear force. The shear bond capacity and deformability of the half-pipe shear connectors are strongly affected by the thickness-to-diameter ratio. Additionally, the shear strengths of the hollow shear connectors (i.e. the half-pipe and the channel shear connectors) are compared. Furthermore, shear capacities of the hollow shear connectors equivalent to headed stud connectors are also discussed.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.813-820
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• 2003

The shear friction tests using large direct shear test units were performed to evaluate the friction properties of fiber-mixed soil. The used materials and test conditions were flowing. Soils : SM and ML; mixing fibers : three types of polypropylene fibers(net type 38mm and 60mm, and line type 60mm), reinforcement : geogrid; mixing ratio：0.2% and 0.3%; degree of compaction : 85% and 95%. In the test results, the reinforcing effect of fiber mixed soil was confirmed.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.366-369
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• 2006

Deformability of RC members in shear is controlled by governing failure modes and material strength. Shear strength of members in D-regions has been explained by a direct load path (direct strut or arch action) and indirect load path (fan action or truss action). Indirect load path including truss action and fan action rely on bond along tension ties. Generally, superposition of two actions results in total shear strength when shear failure modes control. The ultimate deformation depends on controlling failure modes and thereby, their force transfer patterns. Proposed models are capable of explaining of limited deformability of RC members in D-regions.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.261-264
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• 2006

Deformability of RC members in shear after flexural yielding is limited and controlled by governing failure modes and material strength. Shear strength of members in D-regions has been explained by a direct load path (direct strut or arch action) and indirect load path (fan action or truss action). Indirect load path including truss action and fan action rely on bond along tension ties. Generally, superposition of two actions results in total shear strength when shear failure modes control. The ultimate deformation depends on controlling failure modes and thereby, their force transfer patterns. Proposed models are capable of explaining of limited deformability of RC members in D-regions.

• Geomechanics and Engineering
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• v.25 no.2
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• pp.89-98
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• 2021

The paper presents an experimental study on the strength behaviour of a coral gravelly sand from Vietnam subjected to monotonic and cyclic loading. A series of direct shear tests were carried out to investigate the shear strength behaviour and the factors affecting the shear strength of the sand such as relative density, cyclic load, amplitude of the cyclic load and loading rate. The study results indicate that the shear strength parameters of the coral gravelly sand include not only internal friction angle but also apparent cohesion. These parameters vary with the relative density, cyclic load, the amplitude of the cyclic load and loading rate. The shear strength increases with the increase of the relative density. The shear strength increases after subjecting to cyclic loading. The amplitude of the cyclic load affects the shear strength of coral gravelly sand, the shear strength increases as the amplitude of the cyclic load increases. The loading rate has insignificantly effect on the shear strength of the coral gravelly sand.

• Journal of Ocean Engineering and Technology
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• v.25 no.3
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• pp.34-39
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• 2011

This study investigated the shear and CBR characteristics of dredge soil-bottom ash-waste tire powder-mixed lightweight soil, which was developed to recycle dredged soil, bottom ash, and waste tire powder. Test specimens were prepared with various contents of waste tire powder ranging from 0 to 100% at 50% intervals by the weight of the dry dredged soil. Several series of triaxial compression tests and CBR tests were conducted. The shear strength characteristics of the lightweight soil were compared using two different shear tests (triaxial compression test and direct shear test). The experimental results indicated that the internal friction angle of the lightweight soil obtained by the direct shear tests was greater than that by the triaxial shear tests. However, the cohesion value obtained by the triaxial shear tests was greater than that by the direct shear tests. The CBR value of the lightweight soil decreased from 35% to 15% as waste tire powder content increased.

• Geomechanics and Engineering
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• v.28 no.2
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• pp.135-143
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• 2022

Soils are natural granular materials whose mechanical properties differ according to the size and composition of the particles, so soils exhibit an obvious scale effect. Traditional soil mechanics is based on continuum mechanics, which can not reflect the impact of particle size on soil mechanics. On that basis, a matrix-reinforcing-particle cell model is established in which the reinforcing particles are larger-diameter sand particles and the matrix comprises smaller-diameter bentonite particles. Since these two types of particles deform differently under shear stress, a new shear-strength theory under direct shear that considers the stress concentration and bypass phenomena of the matrix is established. In order to verify the rationality of this theory, a series of direct shear tests with different reinforcing particle diameter and volume fraction ratio are carried out. Theoretical analysis and experimental results showed that the interaction among particles of differing size and composition is the basic reason for the size effect of soils. Furthermore, the stress concentration and bypass phenomena of the matrix enhance the shear strength of a soil, and the volume ratio of reinforcing particles has an obvious impact on the shear strength. In addition, the newly proposed shear-strength theory agrees well with experimental values.

• Tunnel and Underground Space
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• v.5 no.2
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• pp.104-113
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• 1995

Shear strength of the discontinuity on which the pre-failure of rock slope was occurred during surface excavation was measured through the direct shear test using core samples obtained in-situ. Internal friction angle was increased as the roughness of discontinuity surface(JRC) was increased. Results of the tilt test using core samples of higher JRC also showed very similar trend as those of the direct shear test. When the samples replicated from natural cores were used int he tilt test, results of friction angles showed almost perfect continuation of the residual friction angles from the direct shear test. However, when the gouge material existed in the discontinuity the internal friction angle strongly depended upon the rate of filling thickness to the height of asperity irrespective of the JRC. Based on the results of both direct shear test and tilt test internal friction angle and cohesion of discontinuity, which reflect the in-situ conditions fo pre-sliding failure and also can be used for the optimum design of support system, were assessed. Two kinds of support measures which were expected to increase the stability of rock slope were considered; lowering of slope face angle and installation of rock cable. But, it was found that the first method might lead to more unstable conditions of rock slope when the cohesion of discontinuity plane was negligibly low and in that case the support systems of any kind which could exert actual resisting force were needed to ensure the permanent stability of rock slope.

• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.5-14
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• 2008

Shear characteristics of quarry blasted rocks were compared using large scale direct shear tests and triaxial tests. For comparison purpose, similar test conditions were simulated as much as possible and three types of relative density (50%, 70%, 90%) were employed for the test. Results indicate that stress-strain behavior shows the same trend for two tests, but the measured shear strengths differ for the different test ms and depends on the relative density. At low relative density, the internal friction angles from direct shear test are smaller than those from triaxial tests. However, at high relative density, this phenomenon is reversed.