(1) The flow properties of loose ore
Many scientific and technological workers have studied and measured the fluidity of ore in the mine. Brown and Hawkslev describe the free-flowing material near the discharge port as shown in Figure 1. Kvapil further studies the flow band, and its mode is shown in Figure 2. He believes that the formation of the flow belt depends on the nature of the material.
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A material flow function FF
Jenike proposed to describe the fluidity of the material by the material flow function FF.
As shown in Figure 3, the strength of the bulk material is highly dependent on the degree of pre-compaction. It is envisaged that in a cylindrical cylinder without friction in a cylinder, a loose material (within a certain time) is compacted under a certain pressure σ 1 , and then the cylinder is removed, and a load is applied to the sample, causing The pressure required to destroy the specimen is f c (open yield strength). Then, the flow function:
FF=ƒ(σ 1 )=σ 1 /ƒ c (1)
It is difficult to measure σ 1 and there are many methods. There is a device called "closed destroyer", and a device for compressing the material in a cylinder with a Teflon film, which can directly measure σ 1 ; Jennick's indirect method is to cut The instrument (Fig. 4) was tested to obtain the yield trajectory of the sample. The σ 1 value can be represented by a two molar (Mohr) circle on the yield trajectory, as shown in Fig. 5.
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B material internal friction angle δ' and effective internal friction angle δ
The angle δ' of the line connecting the yield trajectory with the molar circle tangent to the σ n- axis is the internal friction angle of the material; the tangential line tangent to each molar circle is the same as the σ n- axis The angle δ is the effective internal friction angle. As shown in Figure 6.
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