• Geomechanics and Engineering
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• 제9권5호
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• pp.601-618
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• 2015

Soil-reinforcement interaction mechanism is an important issue in the design of geosynthetic reinforced soil structures. This mechanism depends on the soil properties, reinforcement characteristics and interaction between these two elements (soil and reinforcement). In this work the shear strength of sand/geotextile interfaces were characterized through direct and simple shear tests. The direct shear tests were performed on a conventional direct shear device and on a large scale direct shear apparatus. Unreinforced sand and one layer reinforced sand specimens were characterized trough simple shear tests. The interfaces shear strength achieved with the large scale direct shear device were slightly larger than those obtained with the conventional direct shear apparatus. Notwithstanding the differences between the shear strength characterization through simple shear and direct shear tests, it was concluded that the shear strength of one layer reinforced sand is similar to the sand/geotextile interface direct shear strength.

• Geomechanics and Engineering
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• 제25권2호
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• pp.89-98
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• 2021

The paper presents an experimental study on the strength behaviour of a coral gravelly sand from Vietnam subjected to monotonic and cyclic loading. A series of direct shear tests were carried out to investigate the shear strength behaviour and the factors affecting the shear strength of the sand such as relative density, cyclic load, amplitude of the cyclic load and loading rate. The study results indicate that the shear strength parameters of the coral gravelly sand include not only internal friction angle but also apparent cohesion. These parameters vary with the relative density, cyclic load, the amplitude of the cyclic load and loading rate. The shear strength increases with the increase of the relative density. The shear strength increases after subjecting to cyclic loading. The amplitude of the cyclic load affects the shear strength of coral gravelly sand, the shear strength increases as the amplitude of the cyclic load increases. The loading rate has insignificantly effect on the shear strength of the coral gravelly sand.

• KCI Concrete Journal
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• 제12권1호
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• pp.91-99
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• 2000

A new type of retrof=t anchor bolt that uses deformed reinforcing bars and a commercial adhesive was developed and then an experimental study was carried out to determine the behavior of the anchors in direct shear. The steel-to-concl몫ete interface was tested. Plain concrete slabs with about 20-MPa compressive strength were used for 23 direct shear tests performed Test variables were anchor diameters (D16, D22. and D29) and edge effect. Three different shear tests were completed: simple shear, edge shear where anchors were pulled against the concrete core, and edge shear where anchors were pushed against the concrete cover In the simple and the edge shear tests where the anchors were pulled against the core, the theoretical dowel strength determined by (equation omitted) was achieved but with relatively large displacements. The shear resistances increased with the increasing displacements. In the edge shear test where the anchors were pushrd against the cover, the peak shear strengths signif=cantly lower than the theoretical dowel strength were determined due to cracks developed in concrete when the edge distance was 80 mm. The peak strengths were about 50% of the dowel strength for Dl6 bar. and about 25% or less of the dowel strength for D22 and D29 bars. Test results revealed that the edge shear where the anchor was pushed against the cover controled.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.423-430
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• 1999

A weathered residual soil is a soil-like material derived from the in situ weathering and decomposition of rock which has not been transported from its original location. Undisturbed sampling of residual soils is extremely difficult, which has an important effect on investigating the strength and compression characteristics. Thus, a special undisturbed sampling device (direct shear box with shoe) was developed and undisturbed samples were successfully obtained for direct shear tests, Direct shear testing was conducted under unsoaked and soaked condition. As a result, the shear strength of soaked samples was less than that of unsoaked samples, and it was verified that direct shearing of undisturbed samples can evaluate reasonably the shear strength and the slope stability.

• 한국지반공학회논문집
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• 제15권5호
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• pp.125-139
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• 1999

풍화잔적토는 불교란 시료를 채취하기가 곤란하기 때문에 전단강도를 산정하는데 있어서 어려움을 겪고 있다 본 연구에서는 직접 전단시험용 불교란 시료를 용이하게 채취하기 위해서 슈 장착 직접 전단상자를 개발하였으며, 성공적으로 불교란 시료를 채취할 수 있었다. 채취된 분교란 시료의 직접 전단시험을 통해서 포화조건에 따른 전단강도의 변화를 규명하였다. 그리고 교란에 따른 풍화잔적토의 전단거동을 규명하기 위해서 정적시료 성형장치를 제작하였고, 자연함수비 상태에서는 교란에 따른 강도저하가 나타나지만, 수침시에는 강도가 유사함을 확인하였다. 불교란 시료에 대해서 직접전단시험과 삼축압축시험시의 강도를 비교한 결과, 직접 전단시험시 수침시료의 강도가 삼축압축시험의 결과와 유사한 경향을 나타내었다. 그리고 대상 붕괴사면에 대한 역해석을 수행한 결과, 슈 장착 직접 전단상자를 이용하면 풍화잔적토 사면에서의 전단강도 산정이 가능하리라고 판단되었다.

• 한국지반신소재학회논문집
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• 제15권4호
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• pp.63-69
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• 2016

본 논문은 삼축압축시험(CD)과 개선된 직접전단시험 결과 얻어진 불포화토의 전단특성을 비교분석하여 새로이 개선된 직접전단시험장비의 실용성을 검증하였다. 2010년 경기도 양평군 토석류 발생사면에서 채취한 시료를 대상으로 불포화토 상태의 전단강도실험을 수행하였다. 다른 두 종류의 실험방법에서 낮은 모관흡수력이 작용하는 경우는 전단강도와 선형적인 관계를 나타내며, 모관흡수력의 증가함에 따라 불포화토의 겉보기 점착력 역시 선형적으로 증가하였다. 다른 두 실험장비에 의한 결과를 비교한 결과, 산정된 불포화토의 강도정수($c^{\prime}$, ${\phi}^b$)는 전단 상자의 구속효과가 있는 개선된 직접전단시험에서 다소 크게 나타났다.

• 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.

• 대한치과교정학회지
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• 제21권3호
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• pp.513-520
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• 1991

The purpose of this study was to compare the bracket placement and the shear bond strength of indirect-bonded brackets with those of direct-bonded ones. Forty eight extracted human teeth were collected and attached with brackets and tested on shear bond strength, using Instron. Fourteen patients from Wonkwang University Dental Hospital were selected for direct bonding of brackets and their teeth were measured on bracket angulation and bracket height. The obtained results were as follows: 1. The shear bond strengths of incisors were higher in direct-bonding,group, rather than in-direct-bonding group. But, the shear bond strength of premolars showed no significant differences between groups. 2. The bracket angulations of indirect-bonding group were preciser than those of direct-bonding group, especially in upper first premolars, lower lateral incisors, canines, premolars. 3. In bracket height, there were no significant differences between groups.

• 한국지반환경공학회 논문집
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• 제18권2호
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• pp.29-37
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• 2017

집중호우로 인하여 산악지반에 발생하는 토석류의 거동은 대상지반 세립분의 전단강도 및 유변학적 특성들에 의하여 영향을 받기 때문에, 두 특성에 대한 정수는 토석류 거동을 파악하는데 매우 중요한 요소이다. 본 연구에서는 직접전단 실험을 통하여 세립분의 전단강도 및 유변학적 정수를 평가하고자 하였다. 건조상태와 액성한계상태로 조성된 두 가지 세립분 시료에 대하여 직접 전단실험을 수행하였으며, 연직응력에 따른 전단강도를 측정하여 점착력과 내부마찰각을 산정하였다. 또한 액성한계로 조성된 시료의 잔류전단강도를 획득하기 위하여 전단변형률속도와 전단방향을 변화시켜 반복전단실험을 수행하였다. 실험 결과, 액성한계상태의 시료는 건조 상태 시료에 비해 내부마찰각은 작지만 점착력은 더 큰 것으로 나타났으며, 잔류전단강도를 통해 산정한 내부마찰각과 점착력은 첨두전단강도에 의해 산정된 결과보다 작은 것으로 나타났다. 반복전단 결과, 전단변형률속도와 잔류전단강도는 선형적인 관계를 보였으며, 전단변형률속도-잔류전단강도 관계의 기울기로써 결정되는 점성은 약 $73.60Pa{\cdot}s$로 산정되었다. 본 연구는 직접전단 장비가 산악지반 토석류 거동과 관련된 세립분의 전단강도 및 유변학적 정수 산정에 효과적으로 활용될 수 있음을 보여준다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.293-302
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• 2010

2 types of geogrids and geotextiles was used to evaluate shear behaviors after installation damage test. Shear behaviors were compared after installation damage test and coefficient of resistance to direct sliding($f_{ds}$) was estimated by theoretical shear analysis. Shear strength of damaged geogrid decreased under high normal stress of 150kPa and shear strength of geotextile decreased with increasing normal stress. It is seen that $f_{ds}$ values after installation damage decreased than before installation damage through comparison calculated $f_{ds}$ by direct theoretical shear analysis. $f_{ds}$ values to be calculated by theoretical shear analysis were changed with before and after installation damage.