• Title/Summary/Keyword: peak friction angle

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Selection of design friction angle: a strain based empirical method for coarse grained soils

  • Sancak, Emirhan;Cinicioglu, Ozer
    • Geomechanics and Engineering
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    • v.20 no.2
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    • pp.121-129
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    • 2020
  • In the design of geotechnical structures, engineers choose either peak or critical state friction angles. Unfortunately, this selection is based on engineer's preference for economy or safety and lacks the assessment of the expected level of deformation. To fill this gap in the design process, this study proposes a strain based empirical method. Proposed method is founded on the experimentally supported assumption that higher dilatancy angles result in more brittle soil response. Using numerous triaxial test data on ten different soils, an empirical design chart is developed that allows the estimation of shear strain at failure based on soil's peak dilatancy angle and mean grain diameter. Developed empirical chart is verified by conducting a small scale retaining wall physical model test. Finally, a design methodology is proposed that makes the selection of design friction angle in structured way possible based on the serviceability limits of the proposed structure.

The Effects of Chlorination on the Friction Properties of SBR (염소화 반응조건이 SBR의 표면마찰 특성에 미치는 영향)

  • Park, Cha-Cheol;Kim, Ho-Jung
    • Fashion & Textile Research Journal
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    • v.10 no.1
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    • pp.101-105
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    • 2008
  • This study was concerned with the influence of reaction conditions on the surface friction properties of Syrene-Butadiene Rubber(SBR) sheet when it was chlorinated by chemical treatment method using the sodium hypochlorite and sulfuric acid. The results of this study were as follows. SEM photographs of chlorinated SBR surface showed uneven etching caused by the chlorination. In the FTIR spectra, the intensity of C=C peak of SBR was decreased with increasing the concentration of sodium hypochlorite. Otherwise there was no trace of C=C peak in spectrum of SBR treated with 5 wt% NaOCl with pH 0.1 for 90 seconds. EDX spectra showed that relative content of chlorine of SBR was increased with increasing the amount of sodium hypochlorite, and also affected with pH condition of acid solution. Friction angle and friction coefficient of SBR were influenced with concentration of sodium hypochlorite, but were not with pH condition of acid solution.

Critical State of Crushable Jeju Beach Sand (파쇄성이 큰 제주해사의 한계상태 특성)

  • Lee, Moon Joo;Bae, Kyung Doo;An, Sung Mo;Lee, Woo Jin
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.2C
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    • pp.133-140
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    • 2010
  • A series of triaxial test was performed in order to determine critical state parameters of calcareous Jeju sand, which comprises angular shape particles with many pores in the surface. It is observed that Jeju sand mainly shows the contractive behavior during triaxial shear due to high extreme void ratios and large compressibility. The peak friction angle of Jeju sand decreases slightly with increasing mean effective stress due to the particle crushing of carbonate materials. However, the peak friction angle of Jeju sand is higher than that of other silica sands because of the more angular particle shape. The critical state friction angle of Jeju sand gradually decreases when the mean effective stress at a critical state increases. Whereas, there is not a clear influence of void ratio on the critical state friction angle. Critical state parameters of Jeju sand are similar to those of calcareous sands, but significantly larger than those of common sands.

Using grain size to predict engineering properties of natural sands in Pakistan

  • Aziz, Mubashir
    • Geomechanics and Engineering
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    • v.22 no.2
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    • pp.165-171
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    • 2020
  • Laboratory determination of strength and deformation behavior of clean sands and gravels has always been challenging due to the difficulty in obtaining their undisturbed samples. An alternative solution to this problem is to develop correlations between mechanical properties of cohesionless soils and their gradation characteristics. This study presents database of 3 natural sands with 11 varying particle size gradation curves to allow investigating relationships between mean particle size, maximum and minimum void ratio, relative density and shear strength of the test soils. Direct shear tests were performed at relative densities of 50, 75 and 95% to explore the effects of gradation and density on the angle of internal friction of the modeled sand samples. It is found that the mean grain size D50 bears good correlations with void ratio range (emax - emin) and peak angle of internal friction 𝜙'peak. The generated regression models are in good agreement with published literature and can be considered as reliable for natural sands in Pakistan. These empirical correlations can save considerable time and efforts involved in laboratory and field testing.

Experimental Study on Reinforcement Effectives of Soil Shear Strength by Bamboo(Substitute Materials Simulating a Root System) -Analysis caused by Simple Shear Test under Soil Suction Control- (대나무(대체근계)의 토질강도보강효과에 대한 실험적 연구 -토양수분제어하의 단순전단시험에 의한 해석-)

  • Lee, Chang-Woo
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.7 no.2
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    • pp.46-51
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    • 2004
  • In this paper, reinforcement of soil shear strength by bamboo(substitute materials simulating a root system) are evaluated by soil strength parameters(apparent cohesion(c) and internal friction angle(tan${\Phi}$)), using simple shear tester which clearly depicts shear deformation and controls soil suction. The results show that the internal friction angle does not change under various soil suction conditions but the apparent cohesion, which reach a peak in suction of 45cm$H_2O$ near critical capillary head, is effected by soil suction. And the reinforcement of soil strength by bamboo are expressed by apparent cohesion more than internal friction angle. In addition the increment of apparent cohesion by bamboo reached a peak in suction 45cm$H_2O$ too.

Shear Resistance of Sandy Soils Depending on Particle Shape (모래 입자의 형상과 내부마찰각의 상관관계에 관한 연구)

  • Suh, Hyoung Suk;Jo, Yumin;Yun, Tae Sup;Kim, Kwang Yeom
    • Journal of the Korean Geotechnical Society
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    • v.32 no.6
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    • pp.41-48
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    • 2016
  • This study presents the correlations between quantified particle shape parameters and internal friction angles for nine sand specimens including six natural sands and three crushed sands. Specimens are subjected to 3D X-ray computed tomographic imaging and their particles are segmented through the aid of image processing techniques. Shapes of segmented particles are then quantified through two shape parameters such as sphericity and elongation. The direct shear apparatus enables us to measure peak and critical state friction angles of sand specimens of distinct relative densities. The gathered data show that decreasing sphericity and increasing elongation cause increases in peak and critical state friction angle with similar gradients.

Effect of roughness on interface shear behavior of sand with steel and concrete surface

  • Samanta, Manojit;Punetha, Piyush;Sharma, Mahesh
    • Geomechanics and Engineering
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    • v.14 no.4
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    • pp.387-398
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    • 2018
  • The present study evaluates the interface shear strength between sand and different construction materials, namely steel and concrete, using direct shear test apparatus. The influence of surface roughness, mean size of sand particles, relative density of sand and size of the direct shear box on the interface shear behavior of sand with steel and concrete has been investigated. Test results show that the surface roughness of the construction materials significantly influences the interface shear strength. The peak and residual interface friction angles increase rapidly up to a particular value of surface roughness (critical surface roughness), beyond which the effect becomes negligible. At critical surface roughness, the peak and residual friction angles of the interfaces are 85-92% of the peak and residual internal friction angles of the sand. The particle size of sand (for morphologically identical sands) significantly influences the value of critical surface roughness. For the different roughness considered in the present study, both the peak and residual interaction coefficients lie in the range of 0.3-1. Moreover, the peak and residual interaction coefficients for all the interfaces considered are nearly identical, irrespective of the size of the direct shear box. The constitutive modeling of different interfaces followed the experimental investigation and it successfully predicted the pre-peak, peak and post peak interface shear response with reasonable accuracy. Moreover, the predicted stress-displacement relationship of different interfaces is in good agreement with the experimental results. The findings of the present study may also be applicable to other non-yielding interfaces having a similar range of roughness and sand properties.

Evaluation of Shear Strength of Rockill Materials Considering Dilatancy Effect (Dilatancy효과를 고려한 사석재료의 전단강도 평가)

  • 신동훈;이경필
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.10a
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    • pp.265-270
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    • 2002
  • Dilatancy is a unique characteristics of granular materials showing the tendency to change volume upon shearing. In this study large triaxial tests were peformed for both the well graded rock and the poorly graded rock. And the shear strength of rockfill materials considering dilatancy is evaluated based on the test results. For the rock materials of this study the contribution of dilatancy in the maximum internal friction angle is as much as -6.0%∼3.0% of the internal friction angle measured at peak

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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.

Nonlinear Strength Parameters and Failure Characteristics of Anisotropy Rock - Shales (혈암의 이방성을 고려한 비선형 강도정수 및 파괴규준식 산정)

  • 김영수;이재호;허노영;방인호;성언수
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.11a
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    • pp.713-720
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    • 2000
  • The directional response of strength and deformation on the rocks acting by external loads is called by strength and deformability anisotropy, respectively. Peak strength and its failure criteria of anisotro rocks have been studied and reported. Many authors have investigated in detail the behavior of triaxial peak strength of anisotropic rocks(Jaeger 1960, McLamore & Gray 1967, Hoek & Brown 1980, Ramamurthy & Rao 1985). They concluded that the triaxial strength of anisotropic rocks varies according to the inclination of discontinuity in specimens. And, the minimun triaxial strength occurs in the specmen with 60° of inclination angle ; and specimens with 0° or 90° inclination have maximum triaxial strength. Based on the experimental result, the behavior triaxial strength is investigated. The triaxial compression tests due to the angle bedding plane have been conducted and the material constants, 'm' and 's', cohesion and angle of friction and nonlinear strength parameters to fit for the failure criterion were derived from the regression analysis. And, the experimental date are employed to examine three existing failure criteria for peak strength, provided by Jaeger, McLamore and Hoek & Brown and Ramamurthy & Rao. For a shale, the suitability of the failure criteiria of triaxial peak strength for anisotropic rocks is discussed.

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