Reference stress

stress levels at which the measurements of stored material properties are carried out. The reference stress is selected to correspond to the stress level in the silo after filling B6 Sampling and preparation of samples

1) Testing shall be carried out on representative samples of the particulate material. The mean value for each material property shall be determined making proper allowance for variation of secondary parameters.

2) The following method of sample preparation shall be used for the tests described in B7.2, B8, B9.1 and B10:

— The sample shall be poured into the test box, without vibration or other compacting forces and the reference stress ar applied. A top plate shall be rotated backwards and forwards three times through an angle of 10 degrees to consolidate the sample (Figure B1).

3) The mean test values shall be adjusted by conversion factors to derive extreme values. The conversion factors shall be selected to allow for the influence of secondary parameters, the variability of the material properties over the silo life, and for sampling inaccurancies.

4) The conversion factors for a material property shall be adjusted if the effect of one secondary parameter accounts for more than 75 % of the margin introduced for the material property by the conversion factor.

0 0

Post a comment