• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.45-51
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• 2003

Grouting materials in rock is grouted as vein type along the fault surface by the other way for soil and allow a change of characteristics in rock faults as a result of that. Therefore the deformation characteristics of rock faults after grouting differ as a direction and characteristic of grouted fault and stress condition of field rock. Thereby it must be analyzed the effect for deformation of rock according to characteristics of rock faults and characteristics of grouting materials to accurately evaluate the reinforced effect by grouting. But grouting method used in field until present depends on experience of workers, and inspection for those effects are evaluated by measurement of elastic wave velocity, permeability tests and etc. in field. In this study, it was investigated that the effects for shear characteristics of maximum shear strength, residual shear strength and etc. by comparison and analysis of test results which were worked by direct shear tests of rock faults with changing a type of grouting materials and the grouting depth(t) for average width(a) of fault surface roughness when OPC(Ordinary Portland Cement) and Micro cement was grouted in fault surface of field rock to evaluate characteristicsof the shear deformation for rock fault surface of dam by grouting.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.65-73
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• 2008

In the current practice for slope stability problem in Japan, the shear strength, $\tau$, mobilized along the failure surface is usually estimated based on an empirical approximation in which the cohesion, c, is assumed to be equal to the soil thickness above the supposed slip surface, d(m). This approximation is advantageous in that the result of stability analysis is not influenced by the designers in charge. However, since the methodology has little theoretical background, the cohesion may often be grossly overestimated, and conversely the angle of shear resistance, $\phi$, is significantly underestimated, when the soil thickness above the supposed slip surface is quite large. In this paper, a case record of natural slope failure that took place in Hyogo Prefecture in 2007, is described in detail for the case in which the shear strength along the collapsed surface was carefully examined in a series of direct shear box (DSB) tests by considering the effects of in-situ shear stress along the slip surface. It is demonstrated that the factor of safety agrees with that of in-situ conditions when the shear strength from this kind of DSB test was employed for the back-analysis of the slope failure.

• Journal of the Korean Geosynthetics Society
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• v.5 no.3
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• pp.25-30
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• 2006

Large-scale direct shear tests were conducted in order to evaluate both the shear strength of soil itself and the interface shear strength between soil and woven geotextile. Two types of soil (sand and clay) with a woven geotextile were used in the experimental program. Total nine tests were conducted in this study. It has been found from the experimental results that the friction angle of sand itself were $30^{\circ}$. Interface friction angle between woven geotextile and sand showed $26^{\circ}$ indicating an efficiency of 87%. Similarly, interface friction angle between woven geotextile and clay showed $7.7^{\circ}$.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.25-35
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• 2012

For a member subjected to direct shear forces, forces are transferred across interface concrete area and resisted by shear transfer capacity. Shear-friction equations in recent concrete structural design provisions are derived from experimental test results where shear-friction capacity is defined as a function of steel reinforcement area contained in the interface. This empirical equation gave too conservative values for concrete members with large amounts of reinforcement. This paper presents a method to evaluate shear transfer strengths and to define ultimate conditions which result in crushing of concrete struts after yielding of longitudinal reinforcement perpendicular to the interface concrete. This method is based on the bi-axial stress field theory where different constitutive laws are applied in various means to gain accurate shear strengths by considering softening effects of concrete struts based on the modified compression-field theory and the softened truss model. The validity of the proposed method is examined by applying to some selected test specimens in literatures and results are compared with recent design code provisions. A general agreement is observed between predicted and measured values at ultimate loading stages in initially uncracked normal-strength concrete test.

• Tunnel and Underground Space
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• v.10 no.2
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• pp.173-179
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• 2000

The influence of the plastic flow rules on the elasto-plastic behaviour of a discrete joint element was investigated by performing the numerical direct shear tests under both constant normal displacement and normal displacement conditions. The finite interface elements obeying Plesha’s joint constitutive law was used to allow the relative motion of the rock blocks on the joint surface. Realistic results were obtained in the tests adopting the non-associated flow rule, while the associated flow rule overestimated the joint dilation. To overcome the computational drawbacks coming from the non-symmetric element stiffness matrix in the conventional non-associated plasticity, the symmetric formulation of the tangential stiffness matrix for a non-associated joint element was proposed. The symmetric elasto-plastic matrix it derived by assuming an imaginary equivalent joint with associated flow rule which shows the same plastic response as that of original Joint with non-associated flow rule. The validity of the formulation was confirmed through the numerical direct shear tests under constant normal stress condition.

• Journal of the Korean Geotechnical Society
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• v.38 no.2
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• pp.29-38
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• 2022

The friction anisotropy of shear resistance can be selectively used in geo-structures. For example, larger axially loaded deep foundation, soil nails, and tiebacks increase load carrying capacity due to induced large shear resistance while pile penetration and soil sampling produce minimal shear resistance. Previous studies confirmed direction-dependent shear resistance induced by interface between soil and surface asperity of plate inspired by geometrical shape of snake scale. The aim of this paper is to quantitatively evaluate interface friction angle with different surface asperities. Using the modified direct shear test, a total of 51 cases, which sand are prepared at the relative density of 40%, are conduced including 9 plates, two shear direction (shearing direction against the height of surface asperity is increased or decreased during shearing test), and three initial vertical stress (100 kPa, 200 kPa, 300 kPa). Experimental results show that shear stress is increased with higher height of surface asperity, shorter length of surface asperity, and the shearing direction that the height of surface asperity increases. Also, interface friction angle is decreased with larger surface asperity ratio, and shearing direction with increasing height of surface asperity produces larger interface friction angle regardless of the surface asperity ratio.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.181-194
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• 1999

Both the chemical components and the physical and mechanical properties of the compacted and undisturbed weathered granite soils were estimated to investigate the influences of the degree of weathering and saturation on the shear strength. The weathered granite soils used in this study were taken from six different sites in Korea. The results showed that the shear strength of weathered granite soil decreased with increasing the degree of weathering and saturation. Under the normal stresses less that 40kPa, the shape of Mohr-Coulomb failure envelope followed curved or hyperbolic relationship and a half of cohesion value obtained by the common shear test was observed. Using the Sueoka's method, the values of CWI were ranged from 21.5 to 31.26 which can be characterized as a completely weathered granite soil. Large decrease in shear strength and remarkable variation in dilatancy were observed in saturated granite soil compared to unsaturated soil. It was also found that the shear strength of undisturbed weathered granite soil of Pungam site can be expressed approximately by the equation of ${(\tau)_{sat}= 1.0(\tau)_{unsat}-12.48}$ and this equation can be extended to the other sites considered in this study.

• Geotechnical Engineering
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• v.12 no.6
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• pp.21-36
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• 1996

The stress transfer mechanism between soil and grid reinforcements involves two basic mechanism : frictional soil resistance and passive soil resistance. However the mechanism of the passive soil resistance is very complex to understand. To study the failure mechanism of ribbed reinforcement, the direct shear tests which are dominated by passive soil resistance are analyzed by using the finite element method. The finite element method is used to examine the effects of ribs on this passive soil resistance development and the met hanism of failure. The calculated behavior of the ribbed reinforcement is compared with the measured behavi or. Comparisons between the measured and the simulated strain pat terns, failure modes and load displacement relationship are presented. The behavior of the ribbed reinforcements in a cohesive soil is predicted on the basis of a good agreement between the measured and the Predicted behavior of the Ottawa sand.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.143-149
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• 2016

This study evaluated the shear behavior of geogrid reinforced ballast material using a large scale direct shear test and discrete element method (DEM) based on PFC 3D program. The direct shear test was conducted on ballast materials that have different particle size distributions. Whereas the test results revealed that the shear strength generally increased with the larger particle size of ballast material without geogrid reinforcement, the shear behavior of ballast material was found to change pertaining to the relationship between particle size distribution and geogrid rib size. Generally, it is deemed the effectiveness of reinforcement can be achieved when the rib size is two times greater than average particle size. A numerical analysis based on DEM was conducted to verify the test results. The geogrid modeling was successfully completed by calibration process along with sensitivity analysis to have actual tensile strength provided by manufacturer. With a given geogrid model, the parametric evaluation was further carried out to examine the interactive behavior between geogrid and ballast material. Consequently, it was found that the effectiveness zone of geogrid reinforcement generated within a specific depth.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4C
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• pp.139-147
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• 2012

In this study, various laboratory tests using bottom ash, which has similar engineering properties with sand, were conducted in order to solve the problem of clogging in granular compaction pile and to address sand supply and demand. In particular, testing was performed to help reduce clogging and minimize voids in a crushed stone compaction pile constructed in soft ground. Based on compaction tests and large diameter direct shear tests, an optimum mixing ratio was determined to be 80:20 (crushed stone to bottom ash) because an 80:20 mixing ratio showed the highest shear strength. Test results showed that as the bottom ash content increased above 20%, internal friction angle decreased. Another test method showed freezing and thawing had little effect when the replacement ratio was over 40%. Therefore, bottom ash mixed compaction piles in soft ground are most economical at a 40% replacement ratio.