Answer To: Aim To investigate the parameters that affect the formation of a conical pile and the angle it makes...
David answered on Nov 30 2019
To investigate the parameters that affect the formation of a conical pile and the angle it makes with the ground.
Granular materials are large conglomerations of discrete macroscopic particles. When they are dry, the forces between them are non-cohesive and repulsive. As a result, these granular substances are able to form conical piles under the influence of gravitational force, static friction and collisions. The angel between the soil cone and the horizontal direction obviously depends on the soil parameters such as the internal friction angle, grain size distribution, grain shape, unit weight, moisture content, stratification, segregation, etc. It has been found that the angle of repose strongly depends on material properties such as sliding and rolling frictions (Lee and Herrmann, 1993; Hill and Kakalios, 1995; Zhou et al., 1999) and density of particles (Burkalow, 1945), and particle characteristics such as size and shape (Burkalow, 1945; Carrigy, 1970).
· Affect friction, coefficient of friction:
Gravitational forces exert macroscopic stresses on the conical pile.
Friction is the resistive force among the irregular granular particles. This is very much dependent on the particle surface area as well. Two types of frictional forces exist among the particles. These are Static and rolling frictional forces.
Angle of repose strongly depends on material properties such as sliding and rolling frictions and material density. The investigations of Elperin et al. and Coetzee et al. indicate that the slope angle increases with the increase of friction coefficient shear.
Collisions also results in energy loss due to frictional force generation.
In this case, it is the many particle dynamics that induces the infinite number of collisions. In one dimension, such a collision sequence leaves the particles ‘‘stuck’’ together in close contact with no relative motion.
The term "inter-particle friction" stated by (Yu et al, 1995) includes agglomerate-agglomerate, particle-agglomerate and particle-particle friction in a packing process and excludes the particle friction within agglomerate, which often affects the formation and strength of agglomerates.
In granular materials, particles can either move by rolling or sliding. If the coefficient of friction is over a certain threshold, the particles prefer to move by rolling, if the particles are too rough or too elongated, they do not role, but slide. Whereas for small friction coefficients, also sliding on the ground can occur, for large coefficients of friction the build up of the heaps takes only place via avalanches on the heap surface.
Brown and Bridgwater (1983) considered that the primary factor is the collisions between particles flowing onto the heap and those forming at the surface. As a consequence, small particle velocities will vary with in a wide spectrum, whereas the larger ones will vary with in a narrow interval.
It is generally reported that the angle of repose increases with increasing sliding and rolling friction coefficients and deviation from spheres, and decreases with increasing particle size.
· Particle size
Angle of repose or the angle of the heap will depend on the particle size of the elements that makes up the heap. It can also define as the steepest angle or the angle of the dip at the sideways at which the actual particles start sliding down. This...