Direct shear tests on sand

Jewell, Richard

doi:10.1680/geot.1989.39.2.309

Cited by 116 publications

(53 citation statements)

References 8 publications

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“…The maximum direct shear dilation angle (w d ) values were estimated from the steepest slope (Dvertical displacement/ Dhorizontal displacement) of shear displacement-vertical strain curves [42,54], as shown in Fig. 3b, d, f. Figure 3a, b presents the shear behavior of untreated (m b /m s = 0%) natural soils at an overburden stress of r v-= 50 kPa.…”

Section: Shear Stress and Vertical Strain Behaviors With Shear Displamentioning

confidence: 99%

Shear strength behavior and parameters of microbial gellan gum-treated soils: from sand to clay

2018

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Microbial biopolymers have recently been introduced as a new material for soil treatment and improvement. Biopolymers provide significant strengthening to soil, even in small quantities (i.e., at 1/10th or less of the required amount of conventional binders, such as cement). In particular, thermo-gelating biopolymers, including agar gum, gellan gum, and xanthan gum, are known to strengthen soils noticeably, even under water-saturated conditions. However, an explicitly detailed examination of the microscopic interactions and strengthening characteristics between gellan gum and soil particles has not yet been performed. In this study, a series of laboratory experiments were performed to evaluate the effect of soil-gellan gum interactions on the strengthening behavior of gellan gum-treated soil mixtures (from sand to clay). The experimental results showed that the strengths of sand-clay mixtures were effectively increased by gellan gum treatment over those of pure sand or clay. The strengthening behavior is attributed to the conglomeration of fine particles as well as to the interconnection of fine and coarse particles, by gellan gum. Gellan gum treatment significantly improved not only interparticle cohesion but also the friction angle of clay-containing soils.

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Section: Shear Stress and Vertical Strain Behaviors With Shear Displamentioning

confidence: 99%

Shear strength behavior and parameters of microbial gellan gum-treated soils: from sand to clay

2018

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“…Description of SDST setup is given in literature [1,2]. Figure 3 presents the schematic diagram of the modified direct shear test set-up used in the present study.…”

Section: Design Of Test Setupmentioning

confidence: 99%

“…Several modifications were done to the conventional direct shear test set-up for conducting the tests presented in this paper. The upper half of the shear box is completely modified to obtain more uniform stresses and strains along the shear plane during the test as described in earlier studies [1,2]. The visible front side of the upper half and lower half of the shear box were replaced with a transparent rigid acrylic sheet so as to visualize the particle movement and shear band formation during the tests.…”

Section: Design Of Test Setupmentioning

confidence: 99%

“…The stress-strain response and volume change behavior of sands in shear and interface shear are mainly influenced by the normal stress, method of testing and testing materials [1][2][3][4][5][6], morphological characteristics of sand [7][8][9][10][11][12] and surface roughness of the geosynthetic material at the interface [13][14][15][16][17][18]. Morphological characteristics of sand grains reflect the formation process, transportation process and material composition.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Particle Size on the Friction and Interfacial Shear Strength of Sands of Similar Morphology

Vangla

Latha

2015

Int. J. of Geosynth. and Ground Eng.

130

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Size and morphological characteristics of particles play vital role on the shear and interfacial shear strength of sands. Often, effects of these parameters are merged and cannot be easily separated. Effect of size of the particles on the shear and interfacial shear strength of sands is presented in this paper through direct shear and interface direct shear tests complemented with image analyses and surface roughness studies. To eliminate the effect of morphological characteristics, three sands of different particle sizes with similar morphological characteristics like angularity, roundness, sphericity and roughness were selected for the study. These morphological characteristics for all three sands were determined from the analysis of scanning electron microscope images and were found to be similar for all three sands. It was observed from the symmetric direct shear tests that the particle size has no effect on the peak friction angle when the tests were carried out at same void ratio. However, ultimate friction angles were affected by the particle size. Shear band thickness was estimated from image segmentation analysis of the profiles of colored sand columns during shear and the same was correlated to the particle size. Interface direct shear tests were carried out on sand-geomembrane interfaces to study the effect of particle size on the interfacial shear strength. Microscopic images of geomembranes were captured after the interface shear tests to understand the change in surface roughness of the geomembrane due to particle indentations. Surface roughness studies on geomembrane samples after the tests confirmed that the plowing and groove formation on geomembranes during interface shear tests depend on the particle size as well as the relative roughness of the sand particles with respect to the membrane. Sand of medium particle size showed highest interfacial strength because of more number of effective contacts per unit area of the interface.

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“…Although the Coulomb parameters are, like the rate and state dependent parameters, empirical, they have a significant data base which may help in understanding the underlying processes they describe (e.g. ; WHITMAN and HEALY, 1962;JEWELL, 1989;SWAN et al, 1989;WOOD, 1990;LAJTAI et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

Coulomb constitutive laws for friction: Contrasts in frictional behavior for distributed and localized shear

Marone

Hobbs

Ord

1992

PAGEOPH

105

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Abstract--We describe slip-rate dependent friction laws based on the Coulomb failure criteria. Frictional rate dependence is attributed to a rate dependence of cohesion c and friction angle qS. We show that differences in the stress states developed during sliding result in different Coulomb friction taws for distributed shear within a thick gouge layer versus localized shear within a narrow shear band or between bare rock surfaces. For shear within gouge, shear strength is given by 9 = e cos ~b + an sin qS, whereas for shear between bare rock surfaces the shear strength is ~ = e + a n tan ~b, where z and a~ are shear and normal stress, respectively. In the context of rate-dependent Coulomb friction laws, these differences mean that for a given material and rate dependence of the Coulomb parameters, pervasive shear may exhibit velocity strengthening frictional behavior while localized shear exhibits velocity weakening behavior. We derive from experimental data the slip-rate dependence and evolution of c and q~ for distributed and localized shear. The data show a positive rate dependence for distributed shear and a negative rate dependence for localized shear, indicating that the rate dependence of c and ~b are not the same for distributed and localized shear, even after accounting for differences in stress state. Our analysis is consistent with the well-known association of instability with shear localization in simulated fault gouge and the observation that bare rock surfaces exhibit predominantly velocity weakening frictional behavior whereas simulated fault gouge exhibits velocity strengthening followed by a transition to velocity weakening with increasing displacement. Natural faults also exhibit displacement dependent frictional behavior and thus the results may prove useful in understanding the seismic evolution of faulting.

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Direct shear tests on sand

Cited by 116 publications

References 8 publications

Shear strength behavior and parameters of microbial gellan gum-treated soils: from sand to clay

Shear strength behavior and parameters of microbial gellan gum-treated soils: from sand to clay

Influence of Particle Size on the Friction and Interfacial Shear Strength of Sands of Similar Morphology

Coulomb constitutive laws for friction: Contrasts in frictional behavior for distributed and localized shear

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