• Journal of the Society of Disaster Information
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• v.20 no.1
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• pp.169-176
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• 2024

Purpose: In this paper, an experimental study was conducted to analyze the difference in shear strength caused by the problem of excluding coarse particles due to the size of the test specimen in the direct shear test. Method: A large-scale direct shear test was conducted on three weathered soils containing coarse aggregates with a maximum diameter of 50mm. In addition, a small-scale direct shear test was performed using a sample with a maximum diameter of 5 mm, excluding coarse aggregates. Result: In the case of the small-scale direct shear test, compared to the results of the large-scale direct shear test containing large particles, the internal friction angle was about 2.3% smaller, and there was no significant difference. In terms of cohesion, compared to the large-scale direct shear test, the small-scale direct shear test derived about 80.3% smaller value, showing a relatively large difference. Conclusion: In the large-scale direct shear test, it was analyzed that the coarse particles had a greater impact on the cohesion than the internal friction angle. Therefore, granite weathered clay containing coarse particles is judged to have the same shear strength as the cohesive force that is not affected by vertical stress. In this study, it was analyzed that the small-scale direct shear test, which excludes the coarse particles that are commonly used, provides results on the safety side by excluding the effect of coarse particles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.7 s.250
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• pp.857-864
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• 2006

Various compressive specimens were fabricated using autoclave do-gassing moulding to find out the compressive characteristics of the carbon/epoxy plain weave fabric composites with respect to the bias and shear angles. The stacking angles of the bias specimens are $[0]_{10T,}\;[3]_{10T,}\;[6]_{10T,}\;[9]_{10T,}\;[12]_{10T,}\;[15]_{10T,}\;[30]_{10T,}\;[45]_{10T}$ and those of the sheared specimens are $[{\pm}37]_{10T,}\;[{\pm}32]_{10T,}\;[{\pm}28]_{10T,}\;[{\pm}22]_{10T,}$ respectively. In order to verify the effect of micro-tow structures on compressive strength and modulus of the composites, compressive test specimens of uni-directional carbon/epoxy composites with the same materials and the same stacking conditions were fabricated. The modulus and strength of both types of composite specimens were compared with the prediction results based on the CLPT and a proposed strength formula. The tow deformation and fracture modes were investigated by microscopic observation.

• Journal of the Korean Geotechnical Society
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• v.28 no.3
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• pp.15-23
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• 2012

An internal friction angle, which is one of strength parameters of granular soils, can be obtained from direct shear tests or triaxial tests. The result of traixial tests can be influenced by various experimental conditions such as confining pressure, shearing rate, specimen diameter and height, and end constraint. In this study, undrained and drained shearing behaviors of Nakdong River sand were investigated for loose (Dr = 40%) and dense (Dr = 80%) specimens with 5, 7, and 10 cm in diameter. Friction angles such as undrained total stress friction angle, undrained effective stress friction angle, and drained friction angle obtained from Mohr's stress circle slightly increased and then decreased as a diameter of a specimen increased from 5, 7 to 10 cm, regardless of relative densities. The difference between friction angles caused by different specimen size was at maximum 4.5 degrees for undrained total stress friction angle of dense specimen. In most cases, there was little difference between friction angles of large and small specimens, which was less than 2 degrees. The difference between an effective friction angle from undrained tests and a drained friction angle from drained tests was at maximum 7 degrees for loose samples but negligible for dense samples.

• The Journal of Engineering Geology
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• v.9 no.1
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• pp.69-82
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• 1999

Direct shear tests are perfromed for artifical joint models made of cement with 25 types of different strength and roughness. The tests consist of the multi-stage test which is a common test method for a single joint plane and the test method suggested by ISRM. Then, not only the differences of friction angles between the two test methods are compared, but is the effectiveness of the multi-stage test investigated. The average of friction angles measured from the multi-stage test is $6.4^{\circ}$ lower than that from the ISRM test. Although the strength and roughness of samples vary, the differences of friction angles between the two test methods are constant. The relationship between the shear stress and the normal stress measured from the multi-stage test is well correlate with the Patton's equation. Whereas, the Barton's equation is best fitted with those measured from ISRM test.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.65-73
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• 2012

Soil-rock interface, mainly founded in Granite region of Korea, is known as one of the important factor of the slope failure at the rainfall due to smaller shear strength than soil itself. However, research of the effect on slope stability by soil-rock interfaces is insufficient. Therefore, a series of direct shear tests were performed in order to investigate the effect of soil-rock interface on slope stability. The method of tests is to get sand itself and sand-artificial rock interface shear strength from different grain size of sands and artificial rock samples. The results of tests show that the friction angle of interface depends primarily on particle size and surface roughness. Interface friction angle ratio ${\mu}(={\delta}/{\Phi})$ is in the range of 0.75 ~ 0.96, this results indicate that interface friction angle is smaller than sand itself.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.269-270
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• 2010

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.43-53
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• 2004

The current Korean Concrete Design Code(KCI Code) requires the minimum and maximum content of shear s in order to prevent brittle and noneconomic design. However, the required content of the steel reinforcement In KCI Code is quite different to those of the other design codes such as fib-code, Canadian Code, and Japanese Code. Furthermore, since the evaluation equations of the minimum and maximum shear reinforcement for the current KCI Code were based on the experimental results, the equations can not be used for the RC members beyond the experimental application limits. The concrete tensile strength, shear stress, crack inclination, strain perpendicular to the crack, and shear span ratio are strongly related to the lower and upper limits of shear reinforcement. In this research, an evaluation equation for the minimum content of shear reinforcement is theoretical proposed from the Wavier's three principals of the mechanics of materials.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.357-366
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• 2021

Shear behavior dependent on the shape and roughness of rock joints can greatly influence the stability of the ground and rock structures. The efficient design of rock structures requires understanding of the shear behavior due to joints and accurate calculation of the shear strength. This work reports numerical shear tests using PFC2D on No. 1 (JCR-1), with smooth joints, and No. 7 (JRC-7) and No. 9 (JRC-9), with relatively rough joints, for the 10 shapes of standard joint profiles proposed by Barton and Choubey (1977). The aim was to investigate the shear behavior of rock joints with respect to their roughness. The results show the maximum shear stress to be about 3.2 to 5.0 times greater in the rougher JRC-7 and JRC-9 joints than in smoother JRC-1. The maximum shear displacement was approximately 4.1 to 5.8 times greater at the first normal stress than at the second. The rougher joints showed friction angles of the rock joints that were approximately 1.8 to 3.9 times greater than that in the smooth joint. Overall, increasing the rock joint roughness increased the maximum shear stress and friction angle.

• Composites Research
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• v.18 no.2
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• pp.13-19
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• 2005

In this paper deformation of micro-mechanical parameters such as tow interval, tow thickness and change in tow amplitude are investigated by using dry fabrics (Five-harness satin weave) under shear deformation. To evaluate the observation results according to the generated in-plane forces in the material, bias extension, biaxial test results are compared with. It was found that a picture frame test with a misaligned fibre orientation angle shows large differences in deformation between tensile and compressive tow directions.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.909-914
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• 2008

미세-점착성 퇴적물로 구성되는 퇴적저면의 침식특성을 해석하기 위해, 고령토 퇴적저면에 대한 침식실험이 환형수조를 이용하여 수행되었다. 현재, 퇴적저면의 침식특성 연구에 대한 국내사례는 전무한 실정으로, 본 연구는 퇴적저면에 대한 침식실험 방법 및 결과의 타당성 검증을 목적으로 한다. 이를 위하여, 본 연구에서는 압밀시간 조건에 따라 4가지의 서로 다른 퇴적저면이 조성되었고, 각 저면별로 저면깊이에 따른 저면밀도의 변화가 우선적으로 정밀 측정되었다. 각 퇴적저면별 침식실험으로부터는, 바닥전단응력(${\tau}_b$)의 변화에 따른 저면 침식깊이(즉, 수층 부유사 농도)의 변화 측정을 통하여, 저면깊이에 따른 저면전단강도(즉, 침식한계전단응력, ${\tau}_S$)의 변화 값들이 정량적으로 분석되었으며, 최종적으로 잉여전단응력(${\tau}_b-{\tau}_S$)과 침식률 간의 관계식이 산정되었다. 퇴적저면 침식특성에 관한 과거 해외 연구 결과와의 비교 검토를 통하여, 본 연구에서 사용 혹은 적용된 실험장치, 실험 방법 및 실험결과가 타당성이 있음이 확인되었다.