Department of Physical Properties of Plant Materials

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Determination of basic mechanical properties of granular materials

 

Consolidated bulk density

 

The bulk density is determined from a sample of granular material consolidated in the uniaxial compression tester under the normal stress equal to the vertical silo pressure. Test procedure follows recommendations of the Eurocode 1 design standard.

Wall friction

 

Coefficient of wall friction for the determination of pressures is determined in the Jenike shear tester. The reference stress is equal to the horizontal silo pressure. Test procedure follows recommendations of the Eurocode 1 design standard.

Angle of wall friction for the evaluation of flow is determined with the tilting table method under the reference stress as low as possible to simulate the low pressure occuring during discharge near the outlet of the silo.

Internal friction

 

The angles of internal friction and effective angle of internal friction and cohesion are determined in the Jenike shear tester. Test procedure follows recommendations of the Eurocode 1 design standard.

Pressure ratio

 

The pressure ratio is determined in the uniaxial compression test. The tester measures the horizontal stress. Test procedure follows recommendations of the Eurocode 1 design standard.

Elasticity

 

The modulus of elasticity and the Poisson’s ratio are determined in the uniaxial compression test from the linear part (BC) of the unloading curves: vertical stress-strain and horizontal stress-vertical stress. The tester measures the horizontal stress.

Propagation of accoustic waves in granular materials

Experimental set allowed for generating and recording of shear waves. Values of elastic constants are determined based on measurement of shear wave velocity. Velocity of acoustic shear wave is determined in chamber fitted with piezoelements in top and bottom cover.

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