Behavior of Granular Materials

Record of typical non-reversing stress test on loose sand, K = 2.0, e = 0.87. (From Chaney, R.C., and Fang, H.Y., Static and dynamic properties of marine sediments. Proceedings of the Symposium on Marine Geotechnology and Nearshore/Offshore Structures, Shanghai, China, ASTM STP 923, pp. 74-111, 1986. Reprinted with permission. Copyright ASTM.) 

Corrected cyclic stress ratio and number of load cycles to cause initial liquefaction of sand at different initial relative densities. (From De Alba, P. et al.,. Geotech. Eng. Div., 102,909-927,1976. Reprinted with permission of ASCE.) 

Liquefaction is fundamentally controlled more by shear strain than by shear stress. This results from the generation of pore pressure due to the shear strain breaking down the soil structure and a corresponding tendency to densify. There is a level of shear strain, or threshold shear strain below which no pore pressure is generated. Using the volumetric strain 

Martin et al. (1975) has given procedures to evaluate these two parameters from the results of static rebound tests in a consolidation ring and cyclic load tests on dry sand, respectively. Finn and Bhatia (1981) has also reported good agreement between predicted and measured values using the proposed method. 

A relation has been presented by Martin et al. (1975) that relates the increase in residual pore water (u) for each load cycle to fhe rebound tangent modulus (E ), porosity (n), bulk modulus of an air/water mixture and the volumetric strain per cycle (As d), which is given by Equation 9.17. 

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Equations (1) and (2) are solved by Euler s explicit scheme using finite difference method. The acceleration of a particle can be obtained from the known contact forces, moments, mass and mass moment of inertia. The acceleration is integrated by time to deld the velocity increment and the velocity is integrated again by time to yield the displacement increment. By repeating these processes for all particles, the motion of all particles and the dynamical behavior of granular material can be obtained entirely. Consequently, the unbalanced forces and moments produce the linear and rotational accelerations of particle in the next calculating step successively. 

In the analysis of mechanical behavior of granular materials, the stress path has a very important role. Here we assume the simplest case (Fig. 1) where the stress path is expressed as... 

Figure 1.12 Phases exhibited by granular piles as a function of two control parameters— the aspect ratio a and the inverse container diameter 6 s. Smaller aspect ratio particles show the stick-slip behavior of granular materials, while larger aspect ratio particles act as a solid body when the container is small enough. (From Desmond, K. and Franklin, S.V. Physical Review E, 73(3), 031306, March 2006.)...

N. W. Mueggenburg. Behavior of granular materials under cyclic shear. 

In light of the apparent effect of liquids (water and oil) mechanically attached to the coal, their evaporation, and the restrictions on these vapors release from the coal bed in the oven, a company that specializes in characterizing properties and behavior of granular materials was consulted. A coal blend similar to that used throughout Phase II was evaluated. This study indicated that the rate at which the coal is charged into the oven could affect this component of the forces acting on the walls siuface and cause wall movement and refractory stress. 

Column tests were carried out to investigate the behavior of the materials in a dynamic system. Figure 2 shows the results of these experiments for granular iron hydroxide, Absorptionsmittel 3 and Zr loaded activated carbon. The results of Fe° and activated carbon are not shown in the graph because they had initial high outlet concentrations. 

Previous paragraph was dedicated to the description of spontaneous magnetization of granular metal nanocomposite. In this section, behavior of this material at paramagnetic state (T> Tb) will be discussed. Magnetic moment of a granular metal in this temperature range is induced by the external... 

The size distribution of particles in a wide variety of particulate systems is of paramount importance in the chemical processing industries. For example, the compacting and sintering behavior of metallurgical powders, the flow characteristics of granular material, the hiding power of paint (qv) pigments (qv), and the combustion efficiency of powdered coal (qv) and sprayed fluids, are all heavily influenced by the size of the constituent particles (see Flow... 

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