The Effect of Grain Shape on Side-Wall Pressure in Model Grain Silos

Salem Clay Wright


Granular materials are collections of macroscopic particles, such as corn, rice, and peas. Grain silos store granular particles and are subjected to irregular force build-up, which can have catastrophic results. It has long been observed that the pressure at the bottom of a silo is screened as the silo is filled. The force build-up on the side-walls of grain silos from materials of different aspect ratios, specifically corn, peas, and rice, was studied. The model silo used in the experiment was constructed out of sheet metal pipe 48 inches in length and 6 inches in diameter held in place by a frame constructed of 80/20 aluminum. A hopper with a diameter of 6.5 inches at its widest point and 1.5 inches at the bottom feeds the grain into the silo. Four identical 1.25 inch holes were sawed into the bottom of the wall of the silo to accommodate four force sensors. The four sensors were evenly spaced vertically and used disks of sheet metal approximately 1 inch in diameter screwed into the sensors internal load cell to evenly distribute the applied force. The fill height was approximately 40 inches from the bottom of the silo. Rice was found to exhibit more irregular force build-up, while corn and peas were more regular. Corn and peas followed Gaussian force distributions, but rice was more varied and randomly distributed around the mean force. Corn and peas tended to build up to a final force, while rice reached a maximum and then decreased. Finally, the time at which corn and peas reached a maximum force was more frequently at the end of a run than rice. Rice's irregularity is attributed to its large aspect ratio in comparison to peas and corn.


Granular Materials; Granular Flow;Grain Silos

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