• 한국지반환경공학회 논문집
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• 제13권11호
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• pp.51-60
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• 2012

동토지반의 기초구조물을 설계하는데 있어 기초의 안정성을 지배하는 설계정수인 동결토의 전단강도 및 동착강도를 측정하기 위하여 지난 50여 년 동안 많은 연구가 수행되어 오고 있다. 하지만, 아직까지 동결토의 전단강도 특성에 관한 많은 연구들은 토사 종류, 수직구속응력, 동결온도조건 등 여러 가지 영향인자 중 제한된 영향인자의 변화를 통해 수행되어 왔다. 동결토는 일반 토질과는 달리 토립자, 물, 공기뿐만 아니라 얼음을 포함한 4상으로 구성되어 있으며, 동토의 역학적인 성질의 변화는 일반적으로 온도, 수직구속응력, 동토의 구성물질에 따라 영향을 받는다. 이와 같은 동결토의 전단강도 특성을 측정하기 위하여 영하 30도의 저온환경에서도 동작이 가능하도록 설계된 동결토 직접전단시험기를 활용하였으며, 동토지역의 저온환경을 모사하기 위하여 대형 냉동챔버 내에 직접전단시험기를 설치하였다. 동결토의 전단강도 특성을 측정하기 위하여 비교적 균질한 입경분포를 지닌 주문진표준사 및 실리카모래와 입도분포가 좋은 화강풍화토를 활용하였다. 각각 세가지 시료에 대하여 전단시험은 세가지 동결온도 조건 및 수직구속응력 조건에서 수행되었으며, 그 결과를 바탕으로 동결온도조건 및 수직구속응력이 동결토의 전단강도에 미치는 영향을 분석하였다. 전반적으로 동결토의 전단강도는 동결온도가 낮아질수록 증가하는 경향을 보였으나, 수직구속응력에 의한 영향은 미미한 것으로 나타났다.

• 한국농공학회지
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• 제44권4호
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• pp.123-128
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• 2002

This study was performed to use fiber mixed soil which has clayey soil or sandy soil with fibrillated fiber or monofilament fiber on purpose of construction materials, filling materials, and back filling materials. In addition, this study was conducted to analyze strength properties and fiber reinforcing effect with fiber mixed soil by direct-shear test. In case of fibrillated fiber mixed soil, the more quantity of fiber was in both cohesive soil and sandy soil, the larger shear stress was in respective step of normal load. The respective mixed soil at 0.5% and 0.1% mixing ratio of monofilament fiber mixed soil showed maximum shear stress. According to unconfined compression or direct-shear test, making specimen of the monofilament fiber mixed soil, it is required to be careful and stable mixing method, while it is expected that monofilament fiber mixed soil doesn't increase strength.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1065-1078
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• 2009

The shear strength has been managed as an important factor in soil mechanics. The shear strength estimation model was developed to evaluate the shear strength using only a few soil properties by the linear regression analysis model which is one of the statistical methods. The shear strength is divided into two part; one is the internal friction angle ($\Phi$) and the other is the cohesion (c). Therefore, some valid soil factors among the results of soil tests are selected through the correlation analysis using SPSS and then the model are formulated by the linear regression analysis based on the relationship between factors. Also, the developed model is compared with the result of direct shear test to prove the rationality of model. As the results of analysis about relationship between soil properties and shear strength, the internal friction angle is highly influenced by the void ratio and the dry unit weight and the cohesion is mainly influenced by the void ratio, the dry unit weight and the plastic index. Meanwhile, the shear strength estimated by the developed model is similar with that of the direct shear test. Therefore, the developed model may be used to estimate the shear strength of soils in the same condition of study area.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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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.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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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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• 제28권2호
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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.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
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• pp.86-87
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• 2015

An active study on UHPC, which has been recently used in high-rise building and bridges, is in progress. However, research on bonding shear strength of UHPC is required to be studied due to the lack of information. In this study, experimental research progress for bonding shear strength (shear strength of adhesive surface) evaluation of UHPC (Ultra High Performance Concrete) is proceeded. First, specimens that surface treatment methods of concrete bonded section and retardation time of placement are considered are produced. Second, Direct Shear test is applied on concrete bonded section of UHPC. As a result of this study, the highest bonding shear strength specimen in which compared to the non-retardation time specimen is compaction turbulence treatment. From later study, it is judged that strength of UHPC in accordance with direction of steel fiber when steel fiber of UHPC is mixed.

• 터널과지하공간
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• 제4권3호
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• pp.261-273
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• 1994

Direct shear tests were carried out on the rock joints and artificial discontinuities to investigate the influence of joint roughness on the shear strength and deformation behaviour. Single direct shear testing apparatus used in experiment was designed and manufactured. Its capacity is 200 tons of shear load, 20 tons of normal load and 50$\textrm{cm}^2$ of maximum shear area. Test samples were cement mortar with artificial discontinuity and sandstone with natural joint. Peak shear strength was increased as joint roughness or normal stress was increased, especially, linearly increased with roughness angle in cement mortar. If joint roughness angle was constant at low normal stress, shear strength was not affected by width and height of joint roughness in cement mortar. Peak shear strengths obtained from tests were larger than the values calculated by Barton's equation, and shear stiffness was increased with joint roughness coefficient.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.201-207
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• 2002

An advanced fiber sheet has been widely used for strengthening of the concrete structures due to its excellent properties such as high strength and light weight. Bond strength is very important in strengthening the concrete structures using an advanced fiber sheet. This research examines the bond behavior between fiber sheet and concrete, investigates the bond strength by the direct pull-out test and the tensile-shear test. To obtain the tensile-shear strength a double-face shear type bond test is conducted. The primary test variables are the types of concrete surface roughness (disk-grinding/chipping) and retrofitting methods (bonding/injection). Thirty specimens were tested to evaluate the bond strength. It is shown that the average bond strength between fiber sheet and concrete by the direct pull-out test and the tensile-shear test is $22.3{\sim}23.1kgf/cm^2$ $17.92{\sim}19.75kgf/cm^2$, respectively.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 가을 학술발표회 논문집
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• pp.259-264
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• 2002

In this study the shear strengths of a poorly grad ed rock material(d/sub max/≤50.8mm, C/sub u/=1.86) were determined by large direct shear test and large triaxial test. The obtained stress-strain curves by the above large shear tests for the rock materials are similar to the loose sand's or normally consolidated clay's curve, in which the peak strength does not appear obviously. And for the uniformly graded rock material the shear strength by large direct shear test may be overestimated around 1.54∼1.70 times that of large triaxial test.