Table 7. Primary criteria of moisture content

　

3.3.　Conversion of moisture content ^{1), 2)}

The primary criteria of moisture content, i.e., the moisture content of the samples of which the maximum grain size is 6.7 mm, should be converted to the moisture contents of the samples for the new test procedure to determine the criterion of representing cone penetrating force.

When nickel ore looks wet, it is supposed that water is contained not only in particles but in the void space. In such condition, it is deemed that the particles contain moisture as much as possible. We, therefore, measured the moisture content of particles in the range of 6.7 mm to 19 mm just after wiping the water on each particle soaked into water for long time. The moisture content measured can be regarded as the maximum moisture content in particles.

The moisture content can be converted by the following formula with the maximum moisture content in particles in the range of 6.7 mm to 19 mm and the proportion of particles finer than 6.7 mm in particles up to 19 mm in dry weight:

Table 8 shows the results of the conversion of moisture content. The upper bounds of moisture content in view of prevention of sliding failure of samples for the new test procedure are shown in the bottom of the table.

　

Table 8. Conversion of moisture content

　

3.4.　Relation between moisture content and representing cone penetrating force

To investigate the relation between moisture content and representing cone penetrating force, we carried out the new test procedure for five samples changing moisture content. Fig. 10 shows the relations between moisture content and representing cone penetrating force of the samples of nickel ore. In the figure, the abscissa and ordinate denote moisture content and representing cone penetrating force, respectively. The black circles indicate the measured data. The white circles indicate the upper bounds of moisture content and the representing cone penetrating forces corresponding to them.

3.5.　Criterion for judgment on sliding failure

Based on the results of the tests on the relation between moisture content and representing cone penetrating force, the representing cone penetrating force of each sample corresponding to the criterion of moisture content was analyzed as shown in Fig. 10. The results are shown in Table 9. Based on the values listed in the table, we determined the criterion of representing cone penetrating force at 300 N as a round number of the maximum value of them as illustrated in Fig. 10.

　

Fig. 10.　Relation between moisture content and representing cone penetrating force

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