# Study on the Macro-Fine Mechanical Behavior of Ore Flow Based on the Discrete Element Method
## 4 Flow Characteristics and Stress Distribution of Ore-Rock Bulk
### Lateral Pressure Distribution of the Shaft Wall in the Storage Section  
In the storage section, the important reason for the change of ore-rock stress on both sides of the ore-pass wall is that the particles change their internal spatial distribution and flow characteristics during the flow process [41]. However, because of the effect of the discontinuity of contact between the ore-rock bulk and the ore-pass wall, it is difficult to accurately characterize the change mechanism of the wall stress by the change of the dynamic lateral pressure of the shaft wall. The overpressure coefficient and overpressure times can be used to reveal the mechanical mechanism of the stress change of the ore-pass wall. According to the elevation position of each measuring point, measuring points 1-4 and 5-9 are divided into the lower and the upper part of the storage section, respectively, and the change characteristics of the lateral pressure at each measuring point are gained in real time, as shown in Figure 11.  
It can be seen from Figure 11 that, in the process of ore drawing, the dynamic lateral pressure on the shaft wall of each measuring point basically fluctuates exponentially and decreases, and the pressure value increases gradually from top to bottom (point 9 to 1), while that of some measuring points (point 1 and 3-7) increases significantly compared with the static lateral pressure before ore drawing. The maximum pressure value appears after a period of ore-drawing time, and not at the moment of initial drawing. At the beginning of ore drawing, the loose ore-rock body will produce the phenomenon of the particles' rotation, and they will slip under the action of their own gravity, which breaks the initial mechanical equilibrium and causes the mechanical behavior of \"arch forming-arch collapsing\" continuously inside the stored materials. The formation of the arch, which may be instantaneous and unstable, causes the increase in the lateral pressure value of the measuring point near the arch foot--that is, the \"over-pressure phenomenon\". The collapse of the arch leads to the instantaneous decrease in the lateral pressure value near the measuring point. The phenomenon of \"arch forming- arch collapsing\" occurs alternately in the process of ore-rock flow, which results in the exponential fluctuation decreasing of dynamic lateral pressure at each measuring point and the peak lateral pressure appearing after a period of time. This is consistent with the results of previous research on bulk and spontaneous arch formation during ore-rock flow [42; 43]. Also, the overpressure data at each measuring point of the ore-pass wall under different ore-drawing times are counted in real time, which is shown in Table 4.  
Figure 11: Characteristics of the dynamic lateral pressure change at each measuring point of the shaft wall. It can be seen from Table 4 that the degree of the overpressure phenomenon at each measuring point is different under different ore-drawing times. In the 1-9 measuring points, the accumulated overpressure of point 1 is 15 times, that of point 3 is 3 times, and that of points 4-7 is only 1 time. This indicates that the frequency of the overpressure phenomenon in the lower part of the storage section is much greater than that in the upper part, and the closer the measuring point at the bottom of the storage section, the greater the frequency of the overpressure phenomenon. This is due to the speed and acceleration gradually increasing and the movement intensity of ore-rock particles gradually rising when the ore drawing began. At this time, a strong dynamic load is generated on the wall of the ore storage section, causing the phenomenon of overpressure and the increase in dynamic lateral pressure on the wall. With the continuous increase in ore-drawing times (the total amount of the ore-rock in the shaft is constantly reduced), the dynamic lateral pressure of the wall will inevitably decline even if the movement of the ore-rock particles is intense.