Strona 2_redak - Instytut Agrofizyki im. Bohdana Dobrzańskiego ...

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10.2). The spherical shape of soybeans as compared to the lenticular shape of lentil
seeds results in different distribution of contact points in bedding of material. Almost
vertical orientation of the shortest axes of lentil seeds obtained during filling the
tester results in easier transmission of vertical load into the lateral direction than in
the case of spherical (soybean) or irregularly shaped seeds (pea).
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Fig. 10.7. Comparison of the experimental and theoretical values of the pressure ratio [69]
10.5. Concluding remarks
The values of pressure ratio for tested seeds at all levels of moisture content
were found to be significantly lower than recommended by Eurocode 1 for filling
and storing of cereal grain, and lower than the values obtained from equation 10.8
(table 10.2). Experimental values of the pressure ratio are located near the lower
limit of theoretical values obtained for yielding at the wall in the active stress case
(i.e. for the wall friction angle 3 w approaching zero, fig. 10.7). Lower limit of the
theoretical values of the pressure ratio (dashed line in fig. 10.7 indicated as
3 w0 = 0 o ) comprise the case of yielding at the centre of a silo in the active case
when directions of the principal stresses are vertical and horizontal. This confirms
the opinion that during uniaxial compression test the horizontal and vertical
stresses are approximately principal stresses in the test sample, whereas they may
not be in the silo [50].