• 한국지반공학회논문집
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• 제20권2호
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• pp.75-85
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• 2004

폐기물 매립장의 침출수를 차수하기 위한 목적으로 다양한 토목섬유들이 폭 넓게 사용되어지고 있다. 이런 토목섬유 사이의 접촉 전단강도는 매립장 바닥차수 시스템 및 종료 매립장 커버 시스템 설계 시 구조물의 안전에 중요한 영향을 주는 설계정수임이 틀림이 없다. 본 연구에서는 폐기물 매립장 설계 시 중요한 설계정수인 토목섬유(지오멤브레인과 지오텍스타일 또는 토목섬유 점토 차수재) 사이의 접촉 전단강도를 산정하기 위하여 대형 직접전단 시험을 수행하였다. 특히, 대부분의 토목섬유가 강우, 침출수 및 지하수에 쉽게 영향을 받기 때문에 토목섬유의 접촉 전단강도에 대한 함수비의 영향을 고려한 연구를 수행하였다.

• Structural Engineering and Mechanics
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• 제86권5호
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• pp.663-671
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• 2023

Freeze-thaw cycles induce strength loss at the frozen soil-concrete interface and deterioration of bonding, which causes construction engineering problems. To clarify the deterioration characteristics of the interface under the freeze-thaw cycle, a frozen soil-concrete sample was used as the research object, an interface scanning electron microscope test under the freeze-thaw cycle was carried out to identify the micro index information, and an interface shear test was carried out to explore the loss law of interface shear strength under the freeze-thaw cycle. The results showed that the integrity of the interface was destroyed, and the pore number and pore size of the interface increased significantly with the number of freeze-thaw cycles. The connection form gradually deteriorates from surface-to-surface contact to point-to-surface contact and point-to-point contact, and the interfacial shear strength decreases the most at 0-3 freeze-thaw cycles, with small decreases from to 3-8 cycles. After 12 freeze-thaw cycles, the interfacial shear strength tends to be stable, and shear the failure occurs internally in the soil.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 토목섬유 학술발표회 논문집
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• pp.57-68
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• 1999

This paper summarizes the results of a study which uses the recently developed Optical Profile Microscopy technique (Dove and Frost, 1996) as the basis for investigating the role of geomembrane surface roughness on the shear mechanism of geomembrane/geotextile interfaces. The alternative roughness parameters which consider the direction of shearing are described. These directional parameters are compared with the existing roughness parameters, and the relationship between these directional and non-directional parameters are investigated. Then, the relationship between interface shear strength and surface roughness quantified at the interface is investigated. The results show that interface friction can be quantitatively related to the surface roughness of the geomembrane. The peak and residual interface strengths increase dramatically through the use of textured geomembranes as opposed to smooth geomembranes. For the smooth geomembranes, the sliding of the geotextile is the main shear mechanism. For the textured geomembranes, the peak interface strength is mainly mobilized through the micro-texture of the geomembrane, however, the residual interface strength is primarily attributed to macro scale surface roughness which pulls out and breaks the filaments from the geotextile. The results of this study can be extended to the other interfaces such as joints in rock mass, and also can be used to provide a quantitative framework that can lead to a significantly improved basis for the selection and design of geotextiles and geomembranes in direct contact.

• Geomechanics and Engineering
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• 제23권1호
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• pp.39-50
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• 2020

In order to understand the shear mechanical properties of the interface between clay and structure and better serve the practical engineering projects, it is critical to conduct shear tests on the clay-structure interface. In this work, the direct shear test of clay-concrete slab with different joint roughness coefficient (JRC) of the interface and different normal stress is performed in the laboratory. Our experimental results show that (1) shear strength of the interface between clay and structure is greatly affected by the change of normal stress under the same condition of JRC and shear stress of the interface gradually increases with increasing normal stress; (2) there is a critical value JRC_cr in the roughness coefficient of the interface; (3) the relationship between shear strength and normal stress can be described by the Mohr Coulomb failure criterion, and the cohesion and friction angle of the interface under different roughness conditions can be calculated accordingly. We find that there also exists a critical value JRC_cr for cohesion and the cohesion of the interface increases first and then decreases as JRC increases. Moreover, the friction angle of the interface fluctuates with the change of JRC and it is always smaller than the internal friction angle of clay used in this experiment; (4) the failure type of the interface of the clay-concrete slab is type I sliding failure and does not change with varying JRC when the normal stress is small enough. When the normal stress increases to a certain extent, the failure type of the interface will gradually change from shear failure to type II sliding failure with the increment of JRC.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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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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• 제29권3호
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• pp.281-290
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• 2022

The direct shear test is commonly used to evaluate the shear behavior of frozen soil-structure interfaces under normal stress. However, failure criteria, such as the Mohr-Coulomb failure criterion, are needed to obtain the unconfined shear strength. Hence, the punch shear test, which is usually used to estimate the shear strength of rocks without confinement, was examined in this study to directly determine the adfreezing strength. It is measured as the shear strength of the frozen soil-structure interface under unconfined conditions. Different soils of silica sand, field sand, and field clay were prepared inside the steel and concrete ring structures. Soil and ring structures were frozen at the target temperature for more than 24 h. A punch shear test was then conducted. The test results show that the adfreezing strength increased with a decrease in the target temperature and increase in the initial water content, owing to the increase in ice content. The adfreezing strength of field clay was the smallest when compared with the other soil specimens because of the large amount of unfrozen water content. The field sand with the larger normalized roughness showed greater adfreezing strength than the silica sand with a lower normalized roughness. From the experiment and analysis, the applicability of the punch shear test was examined to measure the adfreezing strength of the frozen soil-structure interface. To find a proper sample dimension, supplementary experiments or numerical analysis will be needed in further research.

• Geomechanics and Engineering
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• 제17권6호
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• pp.553-564
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• 2019

This paper presents experimental results of rock-concrete bi-material discs under cyclically diametrical compression. It was found that both specimens under cyclical and static loading failed in three typical modes: shear crack, tensile crack and a combined mode of shear and wing crack. The failure modes transited gradually from the shear crack to the tensile one by increasing the interface angle between the interface and the loading direction. The cycle number and peak load increased by increasing the interface angle. The number of cycles and peak load increased with the interface groove depth and groove width, however, decreased with increase in interface groove spacing. The concrete strength can contribute more to the cycle number and peak load for specimens with a higher interface angle. Compared with the discs under static loading, the cyclically loaded discs had a lower peak load but a larger deformation. Finally, the effects of interface angle, interface asperity and concrete strength on the fatigue strength were also discussed.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.255-262
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• 1999

This paper summarizes the results of a study which uses the recently developed Optical Profile Microscopy technique (Dove and Frost, 1996) as the basis for investigating the role of geomembrane surface roughness on the shear strength of goomembrane/geotextile interfaces. The results show that interface friction can be quantitatively related to the surface roughness of the geomembrane. The peak and residual interface strengths increase dramatically through the use of textured geomembranes as opposed to smooth geomembranes. For the smooth geomembranes, the sliding of the geotextile is the main shear mechanism. For the textured geomembranes, the peak interface strength is mainly mobilized through the micro-texture of the geomembrane, however, the residual interface strength is primarily attributed to macro scale surface roughness which pulls out and breaks the filaments from the geotextile. The results of this study can be extended to the other interfaces such as joints in rock mass, and also can be used to provide a quantitative framework that can lead to a significantly improved basis for the selection and design of geotextiles and geomembranes in direct contact.

• 한국지반공학회논문집
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• 제18권4호
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• pp.137-146
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• 2002

폐기물 매립지에는 침출수가 외부로 유출되는 것을 방지하기 위해 지오멤브레인, 점토차수재 및 토목섬유 점토 차수재(GCL) 등이 널리 사용된다. 매립지의 사면에 설치되는 GCL과 지오멤브레인 사이의 접촉(interface) 전단강도는 사면에 설치되는 차수 및 최종 덮개시설의 안전한 설계를 위해 꼭 필요한 물성치로서, 본 연구에서는 대형 직접전단 시험기를 사용하여 두 종류의 GCL과 지오멤브레인 사이의 접촉 전단강도를 측정하였다. 본 논문에서는 Mohr-Coulomb 파괴 포락선을 이용하여 전단강도를 평가하였으며, 연직하중, 수화 및 건조상태, 수화조건 등이 전단강도에 미치는 영향을 알아보았다. 분석 결과 연직하중이나 수화 상태가 전단 거동 및 전단 강도에 미치는 영향은 하중의 크기와 토목섬유의 종류에 따라 다르게 나타났다. 6kPa의 하중을 가한 상태에서 수화를 시킨 후 실시한 전단 시험 결과는 기존의 문헌에 제시된 결과와도 잘 일치하는 모습을 보였다. 마지막으로 연직하중 및 수화조건에 따른 마찰각을 제시하여 유사한 토목섬유가 적용되는 현장의 설계시 참고자료로 활용할 수 있도록 하였다.

• 한국지반공학회논문집
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• 제23권10호
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• pp.65-72
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• 2007

본 연구에서는 효율의 관점에서 흙 자체의 전단강도 및 흙/토목섬유 상호간의 접촉면 마찰특성을 조사하기 위하여 대형직접전단시험을 수행하였다. 모래와 쇄석, 3종류의 지오텍스타일(즉, 2종류의 부직포와 1종류의 직포)을 시험에 사용하였다. 접촉면에서의 전단강도를 산정하는데 고려한 접촉면은 모래/모래, 쇄석/쇄석, 모래/직포, 쇄석/직포, 쇄석/부직포-A 그리고 쇄석/부직포-B 등이다. 연구결과, 모래/직포의 접촉면에서는 모래자체의 전단강도(즉, 모래/모래 접촉면)와 비교하여 84%의 효율을 얻었다. 쇄석/부직포-A, 쇄석/부직포-B, 쇄석/직포의 접촉면에서는 쇄석자체의 전단강도(즉, 쇄석/쇄석 접촉면)와 비교하여 각각 74%, 83%, 72%의 효율을 얻었다.