• Title/Summary/Keyword: Interface friction angle

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Characteristics of Friction Angles between the Nak-dong River Sand and Construction Materials by Direct Shear Test (낙동강 모래와 건설재료간의 직접전단시험에 의한 마찰각 특성)

  • Kim, Young-Su;Kim, Dae-Man
    • Journal of the Korean Geotechnical Society
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    • v.25 no.4
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    • pp.105-112
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    • 2009
  • In this study, a series of direct shear tests were performed to investigate the characteristics of friction angles for sands and interface friction angle between sands and construction materials with respect to different relative density of the Nak-dong River sands and shearing velocity. The result of the test shows that friction angles of sands are always higher than interface friction angle between sands and construction materials. As the shearing velocity get faster, the friction angles of sand became higher. With respect to the density of sand by reducing void ratio, friction angles increase linearly, and relevant equations were proposed to calculate the friction angle by changing void ratio and relative density of sand. The interface roughness of construction materials was also an important factor in interface friction angle.

A study on the Measurement of Interface Friction between Soils and Fibers (흙과 섬유의 상호마찰 특성의 측정에 관한 연구)

  • 장병욱;서동욱;박영곤
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 1998.10a
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    • pp.467-472
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    • 1998
  • The interface friction angle between soil and fibers is important to evaluate improvement of the shear strength on fiber mixed soils. Direct shear test and pullout tort conducted by an apparatus made specially for the purpose of this study, was analyzed to know how fiber and soils affect on interface friction angle. By the results, The value of interface friction angle of sandy soils is larger than that of clayey soils. As a diameter of fiber is large, the value of friction coefficient of sandy soil is increase and that of clayey soil is decrease. An interface friction angle of well graded soil is larger value than that of uniform graded soil

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A study on the mechanical properties of geosynthetic interface (토목섬유 접촉면의 역학적 특성에 관한 연구)

  • Nam, Yong;Kim, Gwang-Ho;Im, Jong-Chul;Ju, In-Gon;Kwon, Jeong-Geun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.1540-1549
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    • 2009
  • Shear properties of geosynthetic/geosynthetic and geosynthetic/soil were evaluated from direct shear tests. The type of geosynthetic is Velcro which is effective for geosynthetic interface and make up for the weakness of sandbag. In this study, the cohesion and the angle of internal friction of each interface was estimated. The test results showed that the cohesion and the angle of internal friction of the geosynthetics depended on the amount of normal stress, the type of the geosynthetics used, and combinations of the geosynthetics and soils. Finally, by comparing the apparent cohesion and the friction angle of the geosynthetics, the applicability to design was identified.

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Engineering Properties of Tire Treads for Soil Reinforcement (지반보강재로서 타이어 트레드의 공학적 특성)

  • Yoon, Yeowon;Cho, Sungsoo;Kim, Keunsoo
    • Journal of the Korean GEO-environmental Society
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    • v.8 no.1
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    • pp.49-55
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    • 2007
  • In order to utilize treads of waste tire as reinforcement material it is necessary to know the interface friction angle between tread surfaces and soil and tensile strength of connection joint of tire treads. In this research large direct shear tests were performed to get the interface friction angle between the inner and outer surfaces of treads and soil for different degree of compaction. From the large direct shear tests, the ratio of interface friction angle to the shear friction angle of sand, ${\delta}/{\phi}$, were 1.06 in outside surface of tire tread and 0.93 in inside surface of tire tread. For weathered granite soil the ratio of interface friction angle was 0.98 and 0.92 for outside and inside of tread, respectively. Also tensile tests were performed using universal testing machine for the connection joint of treads and Tirecell units using bolts. The tensile strength of connection joint increased with the number of bolts and with the sizes of washers. Connection by polypropylene ropes showed lower strength than those of bolts.

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Tests of the interface between structures and filling soil of mountain area airport

  • Wu, Xueyun;Yang, Jun
    • Geomechanics and Engineering
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    • v.12 no.3
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    • pp.399-415
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    • 2017
  • A series of direct shear tests were conducted to investigate the frictional properties of the interface between structures and the filling soil of Chongqing airport fourth stage expansion project. Two types of structures are investigated, one is low carbon steel and the other is the bedrock sampled from the site. The influence of soil water content, surface roughness and material types of structure were analyzed. The tests show that the interface friction and shear displacement curve has no softening stage and the curve shape is close to the Clough-Duncan hyperbola, while the soil is mainly shear contraction during testing. The interface frictional resistance and normal stress curve meets the Mohr-Coulomb criterion and the derived friction angle and frictional resistance of interface increase as surface roughness increases but is always lower than the internal friction angle and shear strength of soil respectively. When surface roughness is much larger than soil grain size, soil-structure interface is nearly shear surface in soil. In addition to the geometry of structural surface, the material types of structure also affects the performance of soil-structure interface. The wet interface frictional resistance will become lower than the natural one under specific conditions.

Location determining method of critical sliding surface of fillings in a karst cave of tunnel

  • Lin, P.;Li, S.C.;Xu, Z.H.;Huang, X.;Pang, D.D.;Wang, X.T.;Wang, J.
    • Geomechanics and Engineering
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    • v.16 no.4
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    • pp.415-421
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    • 2018
  • A location determining method is proposed for critical sliding surface in the stability analysis of the filling materials in karst caves. First, a preliminary location of the sliding surface is determined based on simulation results which includes displacement contour and plastic zone. The sliding surface will locate on the bottom contact interface when the friction angle is relative small. However, a weakened contact interface always becomes the critical sliding surface no matter what the friction angle is. Then when the friction angle becomes larger, the critical sliding surface inside fillings can be determined by a parabola, the coefficient of which increases linearly with the friction angle under the same cohesion. Finally, the critical sliding surface approximately remains unchanged with friction angle. The influence of cohesion is similar to that of friction angle. Although affected by shape, size or position of the karst cave, the critical sliding surface mainly depends on both friction angle and cohesion. Thus, this method is always useful in determining the critical sliding surface.

A Study of Characteristic of Friction Angles between Sand and Artificial Rock Interface by Direct Shear Test (직접전단시험에 의한 모래와 인공암석 경계면의 마찰각 특성 연구)

  • Yang, Hong-Suk;Lee, Byok-Kyu;Jang, Seung-Jin;Lee, Su-Gon
    • 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.

An experimental study on shear mechanical properties of clay-concrete interface with different roughness of contact surface

  • Yang, Wendong;Wang, Ling;Guo, Jingjing;Chen, Xuguang
    • Geomechanics and Engineering
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    • v.23 no.1
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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 JRCcr 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 JRCcr 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.

Development and Uncertainty Assessment of Interface Friction Prediction Equation Between Steel Surface and Cohesionless Soils (강재면과 사질토 사이의 경계면 마찰각 예측식 개발 및 불확실성 평가)

  • Lee, Kicheol;Kim, So-Yeun;Kim, Dongwook
    • Journal of the Korean Geosynthetics Society
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    • v.17 no.2
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    • pp.33-40
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    • 2018
  • Characteristics of interface friction between cohesionless soils and geotechnical structure surfaces play an important role in the analysis of earth load and resistance on the structure. In general, geotechnical structures are mainly composed of either steel or concrete, and their surface roughnesses with respect to soil particle sizes influence the interface characteristics between soils and the structures. Accurate assessment of the interface friction characteristics between soils and structures is important to ensure the safety of geotechnical structures, such as mechanically stabilized earth walls reinforced with inextensible reinforcements, piles embedded into soils, retaining wall backfilled with soils. In this study, based on the database of high quality interface friction tests between frictional soils and solid surfaces from literature, equation representing peak interface friction angle is proposed. The influential factors of the peak interface friction angle are relative roughness between soil and solid surface, relative density of frictional soil, and residual (constant volume) interface friction angle. Futhermore, for the developed equation of the interface friction angle, its uncertainty was assessed statistically based on Goodness-of-fit test results.