• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.356-363
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• 2004

In this research, the shear behavior of four different interfaces consisting of 4 types of geosynthetics was examined, and both static and dynamic tests for the geosynthetic interface were conducted. The monotonic shear experiments were performed by using an inclined board apparatus and large direct shear device. The interface shear strength obtained from the inclined board tests were compared with those calculated from large direct shear tests. The comparison results indicated that direct shear tests are likely to overestimate the shear strength in low normal stress range where direct shear tests were not performed. Curved failure envelopes were also obtained for interface cases where two static shear tests were conducted. By comparing the friction angles measured from three tests, i.e. direct shear, inclined board, and shaking table tests, it was found that the friction angle might be different depending on the test method and normal stresses applied in this research. Therefore, it was concluded that the testing method should be determined carefully by considering the type of loads and the normal stress expected in the field.

• Geomechanics and Engineering
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• v.11 no.3
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• pp.345-359
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• 2016

In order to investigate the influence of the interfacial angel on failure characteristics and mechanism of combined coal-rock mass, 35 uniaxial/biaxial compressive simulation tests with 5 different interfacial angels of combined coal-rock samples were conducted by PFC2D software. The following conclusions are drawn: (1) The compressive strength and cohesion decrease with the increase of interfacial angle, which is defined as the angle between structure plane and the exterior normal of maximum principal plane, while the changes of elastic modulus and internal friction angle are not obvious; (2) The impact energy index $K_E$ decreases with the increase of interfacial angle, and the slip failure of the interface can be predicted based on whether the number of acoustic emission (AE) hits has multiple peaks or not; (3) There are four typical failure patterns for combined coal-rock samples including I (V-shaped shear failure of coal), II (single-fracture shear failure of coal), III (shear failure of rock and coal), and IV (slip rupture of interface); and (4) A positive correlation between interfacial angle and interface effect is shown obviously, and the interfacial angle can be divided into weak-influencing scope ($0-15^{\circ}$), moderate-influencing scope ($15-45^{\circ}$), and strong-influencing scope (> $45^{\circ}$), respectively. However, the confining pressure has a certain constraint effect on the interface effect.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.513-518
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• 1998

In Half Precast Concrete Method, such as composite slab and composite wall, Interface between half PC plate and cast-in-place concrete is occurred. And this interface endure lastly in-plane shear which is occurred by external force. Therefore, test was executed to study in-plane shear strength of interface between half PC plate and cast-in-place concrete. In this test, Experimental parameters are finishing condition of the interface, cohesion of concrete, existence and nonexistence of re-bar truss, and angle and direction of lattice of re-bar truss. Comparing and analyzing experimental results, conclusions are obtained as follows. (1) In-plane shear strength of wide interface in composite plate is more affected by the roughness of interface than re-bar truss. And cohesion of concrete contribute to increasing in-plane shear strength. Therefore it seems that the interface should be roughen and kept clean to improve in-plane shear strength. (2) It seems that shear friction equation in ACI code can be sagely available for design of in-plane shear of composite plate.

• Geomechanics and Engineering
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• v.12 no.2
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• pp.211-221
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• 2017

A laboratory investigation into crude oil contaminated sand-concrete interface behavior is performed. The interface tests were carried out through a direct shear apparatus. Pure sand and sand-bentonite mixture with different crude oil contents and three concrete surfaces of different textures (smooth, semi-rough, and rough) were examined. The experimental results showed that the concrete surface texture is an effective factor in soil-concrete interface shear strength. The interface shear strength of the rough concrete surface was found higher than smooth and semi-rough concrete surfaces. In addition to the texture, the normal stress and the crude oil content also play important roles in interface shear strength. Moreover, the friction angle decreases with increasing crude oil content due to increase of oil concentration in soil and it increases with increasing interface roughness.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.285-298
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• 2003

Shear properies of geosynthetic/geosynthetic and geosynthetic/soil interfaces which are widely met in landfill sites were evaluated from the inclined board tests. The inclined board testing apparatus is known to reproduce the shear behavior on the low normal stress most accurately. In this study, the friction angle of each interface was estimated and the tensile force mobilized at the geosynthetic was measured as well. The test results showed that the friction angle of each interface and the tensile force of the geosynthetics depended on the amount of normal stress, the type of the geosynthetics used, and the combinations of geosynthetics and soils. In addition, the sand/geotextile/geomembrane interface system was simulated in this study, and it was observed that the tensile force developed at the geomembrane decreased due to the protection effect of the geotextile located above the geomembrane. The test results of this research was compared with those of direct shear tests published, too. Finally, by comparing the measured tensile force of the geosynthetics when the initial displacement of the box occurs, when the slope is called as the critical slope, with suggested analytic solution, the accuracy of analytic solution and the applicability to design were identified.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.141-144
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• 2000

The slope stability of waste landfill has been a problem in domestic and foreign countries. Waste landfills are being constructed in a reclaimed land or mountainous area. But most of these places are consisted of steep slope and hence it is necessary to use the geosynthetic liners in there. The large size direct shear test(30cm x 30cm) equipment was used to determine the interface friction angles between CCLs and soil & geomembranes. The centrifuge model tests were performed to investigate the slope stability with considering various geosynthetic liners conditions and degree of slope. The results of centrifuge model test indicate that the degree of saturation of GCL, roughness of geomembrane, and slope of landfill have greatly influenced on the slope stability of solid waste landfill.

• Structural Engineering and Mechanics
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• v.2 no.1
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• pp.63-80
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• 1994

A cable is considered as a system of helical wires and a core with distributed dry friction forces at their interfaces. Deformations of the cable subjected to a uniform bending are analyzed. It is shown that there is a critical bending curvature when a slip at the wire-core interface occurs. It originates at the neutral axis of the cross section of the cable and then spreads symmetrically over the cross section with the increase of bending. The effect of slippage on the cable stiffness is investigated. This model is also used to analyze a cable under the quasi-static cyclic bending. Explicit expression for the hysteretic losses per cycle of bending is derived. Numerical examples are given to show the influence of dry friction and helix angle on the bending stiffness and hysteretic losses in the cable.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.61-69
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• 2022

In this study, a large-scale direct shear test was performed to evaluate the shear characteristics of the pile-soil interface according to the fines content and confining pressure conditions as a reasonable evaluation method of the pullout resistance performance of pile considering the soil conditions. It was found that the shear stress was greatly generated under the conditions of high normal stress and low fines content. In addition, the maximum shear stress was found to be rather large under the conditions of the same normal stress and fines content, when pile surface had high roughness. The internal friction angle decreased at the pile-soil interface, when the fines content in the ground increased. On the other hand, the cohesion decreased under the condition of high fines content. And the internal friction angle and cohesion were large regardless of the fines content in the model ground, when the roughness of the pile surface was high.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.496-503
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• 2000

The friction between soils and the geosynthetics varies depending upon the types and characteristics of the involved materials. Many engineers have studied the frictional characteristics between the two materials in may way but the results obtained so far is not satisfactory. In this study the frictional characteristics between the soil and the geogrid were examined through laboratory direct shear test and pull-out test. Tests were conducted on two different types of geogrid: Polyester grids(PET) which are currently used and newly developed fiber-glass grids(FG). Result showed that FG grid yielded smaller displacements and uniform displacement distribution mainly due to much higher stiffness. Therefore, it is expected that more efficientbfl support and displacement control can be achieved by the FG grid.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.265-275
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• 2003

In this study, shaking table tests were conducted to estimate dynamic interface properties between geosynthetics such as geomembrane, geotextile and geosynthetic clay liner. Accelerations of both shaking table and upper box, and relative displacements between geosynthetics under dynamic loading were measured. Also, the influence of normal stress, frequency of excitation and dry/wet conditions were investigated through the analyses of test results. from the test results, it was found that there is a limited acceleration below which dynamic farce can be transmitted between geosynthetics without the loss of horizontal acceleration. Dynamic interface friction angle between geosynthetics could be calculated through the limited acceleration. Relative displacements induced along geosynthetic interfaces under dynamic loading were not consistent depending on the type of interface and test conditions. The maximum slip displacements between geosynthetics are normalized and normalized slip equations were developed for each interface. By using the normalized slip equation, maximum slip displacements for the geosynthetic interface could be predicted for the given base acceleration and frequency of excitation.