Constant-volume friction angle of granular materials: Reply

1989 ◽  
Vol 26 (1) ◽  
pp. 172-172 ◽  
Author(s):  
D. Negussey ◽  
W. K. D. Wijewickreme ◽  
Y. P. Vaid
Keyword(s):  
Granular Materials ◽  
Friction Angle ◽  
Constant Volume

Constant-volume friction angle of granular materials: Discussion

1989 ◽  
Vol 26 (1) ◽  
pp. 170-171 ◽  
Author(s):  
Satoru Shibuya ◽  
Fumio Tatsuoka
Keyword(s):  
Granular Materials ◽  
Friction Angle ◽  
Constant Volume

Constant-volume friction angle of granular materials

1988 ◽  
Vol 25 (1) ◽  
pp. 50-55 ◽  
Author(s):  
D. Negussey ◽  
W. K. D. Wijewickreme ◽  
Y. P. Vaid
Keyword(s):  
Phase Transformation ◽  
Steady State ◽  
Granular Materials ◽  
Friction Angle ◽  
Confining Pressure ◽  
Constant Volume ◽  
Ring Shear ◽  
Ring Shear Apparatus ◽  
Initial Packing ◽  
Undrained Shear

The postulate that the constant-volume friction angle [Formula: see text] of a granular material is unique and a function of mineral composition is verified experimentally. Granular materials comprised of particles ranging from minerals to metals are tested in a ring shear apparatus. Test samples are subjected to large shear displacements until a constant lower bound friction angle [Formula: see text] is mobilized. Possible effects of confining pressure, initial packing density, gradation, and particle shape on the value of [Formula: see text] are investigated. Friction angles mobilized in drained shear at the instant of maximum contraction and in undrained shear at phase transformation and steady state are compared with [Formula: see text] values. The experimental results confirm a broader fundamental significance of [Formula: see text] as a material parameter in that it is a consistent minimum drained friction angle equal to friction angles mobilized at phase transformation and steady state in undrained shear. Key words: granular materials, sand, friction angles, constant volume, steady state, phase transformation state, ring shear test.

Effect of Grain Orientation Distribution on Anisotropy of Idealized Granular Materials

2012 ◽  
Vol 174-177 ◽  
pp. 24-29
Author(s):  
Bo Zhou ◽  
Ji Wei Li ◽  
Peng Shuai
Keyword(s):  
Granular Materials ◽  
Grain Orientation ◽  
Volumetric Strain ◽  
Friction Angle ◽  
Orientation Distribution ◽  
Biaxial Compression ◽  
Shape Effect ◽  
Vertical Loading ◽  
Horizontal Loading ◽  
Long Rod

Abstract. The regular grain orientation of granular materials is a common phenomenon in nature. Based on the research of grain shape effect on mechanical property of granular materials, two kinds of idealized shape grain (kind of long rod and square) assemblies with different grain orientation were studied by simulated biaxial compression test using Discrete Element Method. The significant orientation which can be computed as the mean value of all grain orientation is introduced to represent the orientation regularity of granular materials. In order to study the anisotropy, the mobilized friction angle and volumetric strain of assemblies with different significant orientation were obtained under both vertical and horizontal loading. The results show that the regular orientation of grains influences the movement such as motion and rotation obviously; with the increasing of significant orientation, peak mobilized friction angle of long rod grain assembly gradually increases under horizontal loading, and decreasing under vertical loading.

Unsteady Shear of Dense Assemblies of Cohesive Granular Materials under Constant Volume Conditions

2010 ◽  
Vol 49 (11) ◽  
pp. 5153-5165 ◽  
Author(s):  
Lee R. Aarons ◽  
Jin Sun ◽  
Sankaran Sundaresan
Keyword(s):  
Granular Materials ◽  
Constant Volume

scholarly journals DEM Simulation of Biaxial Compression Experiments of Inherently Anisotropic Granular Materials and the Boundary Effects

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Zhao-Xia Tong ◽  
Lian-Wei Zhang ◽  
Min Zhou
Keyword(s):  
Boundary Conditions ◽  
Granular Materials ◽  
Friction Angle ◽  
Boundary Effects ◽  
Biaxial Compression ◽  
Deformation Pattern ◽  
Compression Tests ◽  
Stress Strain ◽  
Particle Assembly ◽  
Strain Relationship

The reliability of discrete element method (DEM) numerical simulations is significantly dependent on the particle-scale parameters and boundary conditions. To verify the DEM models, two series of biaxial compression tests on ellipse-shaped steel rods are used. The comparisons on the stress-strain relationship, strength, and deformation pattern of experiments and simulations indicate that the DEM models are able to capture the key macro- and micromechanical behavior of inherently anisotropic granular materials with high fidelity. By using the validated DEM models, the boundary effects on the macrodeformation, strain localization, and nonuniformity of stress distribution inside the specimens are investigated using two rigid boundaries and one flexible boundary. The results demonstrate that the boundary condition plays a significant role on the stress-strain relationship and strength of granular materials with inherent fabric anisotropy if the stresses are calculated by the force applied on the wall. However, the responses of the particle assembly measured inside the specimens are almost the same with little influence from the boundary conditions. The peak friction angle obtained from the compression tests with flexible boundary represents the real friction angle of particle assembly. Due to the weak lateral constraints, the degree of stress nonuniformity under flexible boundary is higher than that under rigid boundary.

Motion of a granular avalanche in an exponentially curved chute: experiments and theoretical predictions

1991 ◽  
Vol 334 (1633) ◽  
pp. 93-138 ◽  
Keyword(s):  
Granular Materials ◽  
Friction Angle ◽  
Similarity Solutions ◽  
Initial Condition ◽  
Curvature Effects ◽  
Angle Of Friction ◽  
Theoretical Predictions ◽  
Internal Angle ◽  
Bed Friction ◽  
Granular Avalanche

This paper describes a model to predict the flow of an initially stationary mass of cohesionless granular material down a rough curved bed, and checks it against laboratory experiments that were conducted with several cohesionless granular materials that are released from rest and travel in an exponentially curved chute. We use the depth-averaged field equations of balance of mass and linear momentum as presented by Savage & Hutter (1990). These equations are evolution equations for the transversely averaged stream wise velocity and the distribution of avalanche depths and involve two phenomenological parameters, the internal angle of friction, ϕ, and a bed friction angle, δ, both as constitutive properties of Coulomb-type behaviour. We present the model but do not derive its equations, which are presented in two variants that incorporate weak and strong curvature effects. For granular avalanches which start as parabolic piles, the governing equations (incorporating weak curvature effects) permit similarity solutions. These solutions preserve the parabolic shape and have simple velocity distributions. We present the equations again without detailed explanations. Experiments were performed with seven different granular materials (two classes of glass beads, Vestolen plastic particles, two samples of quartz granules and two types of crunched marmor particles). Piles of finite masses of such granular materials with various initial geometries were released from rest in a 100 mm wide chute having an exponentially curved bed that was lined with Makrolon (a plexiglass), drawing-paper and sandpaper. The granular masses under motion were photographed and video filmed and thus the geometry of the avalanche was recorded as a function of position and time. With all materials and for all the bed linings, the angle of repose and the bed friction angle were determined. The former was identified with the static internal angle of friction. Using a second measuring technique, the effects of the chute walls on the bed friction angle was experimentally determined and incorporated in an effective bed friction angle which thus showed a linear dependence on the pile depth. Coefficients of restitution were also estimated for the particles on the different bed linings. The numerical integration scheme for the general model that was proposed earlier by Savage & Hutter (1989) is a lagrangian finite difference scheme which incorporates numerical diffusion. We present this scheme and analyse its reliability when the numerical diffusion is varied. We also discuss the integration procedure for the similarity solutions. Comparison of the theoretical results with experiments pertain to the similarity model (SM) and the general equation model (GM). Crucial in such comparisons is the identification of initial condition which is not unique from the observational data. For SM it is shown that no initial condition can be found, in general, that would yield computational predictions of the evolution of the position of the leading and trailing edges of the granular avalanche in sufficient agreement with observations. When depth-to-length ratios of the initial pile geometry and the curvature of the bed are sufficiently small, however, then the SM solutions may be used for diagnostic purposes. We finally compare experimental results with computational findings of the GM equations for many combinations of masses of the granular materials and bed linings. It is found that experimental results and theoretical predictions agree satisfactorily if the internal angle of friction, ϕ, exceeds the total bed friction angle, δ, or is not close to it. Limited variations of the bed friction angle along the bed do not seem to have a sizeable effect on the computational results, but it is important that dynamic values rather than static values for ϕ and δ are used in the computations. When δ is very close to ϕ and δ < ϕ , the computational travel time of the granular avalanche exceeds the travel time of experiments considerably. Furthermore, when avalanche masses are reasonably small and coefficients of restitution of the granules on the bed relatively high, again the predictions of the theory overestimate travel times and underestimate avalanche lengths. Thus the theory does seem to be reasonable when the bed friction angle is definitely smaller than the internal angle of friction.

scholarly journals Numerical Triaxial Apparatus and Application

2013 ◽  
Vol 353-356 ◽  
pp. 3251-3255 ◽  
Author(s):  
Xiao Liang Wang ◽  
Jia Chun Li
Keyword(s):  
Granular Materials ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Good Prediction ◽  
Strain Response ◽  
Compression Tests ◽  
Dilatancy Angle ◽  
Triaxial Apparatus ◽  
Dem Model

A numerical triaxial apparatus based on discrete element method is developed on the platform of Yade using Python script. A DEM model with rolling resistance contact considered is proposed for dense granular materials, which is then applied in triaxial compression test of Chende sand. Stress-strain response and volume-axial strain response of the DEM model agree well with that of experiments, with a good prediction of dilatancy angle. Degradation of granular materials duo to particle erosion is also investigated using triaxial compression tests. It is indicated that peak friction angle decreases with the remove of particles if strong force network of granular materials is destroyed.

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