Distinct Element Analysis On Lateral Pressure Of Silo Based On PFC3D

Silo is a common structure of granular material storage，Because of its highstorage efficiency and easy to implement mechanization and automation, it is widelyused in food, coal, chemicals, cement and other industries among. As the silocollapsing accidents continue to occur, silo safety issues are valued by the people.The Janssen formulas only considered the static lateral pressure of silo, therefore, thedesign specifications based on this formula can only guarantee the safe use in a staticcondition, and can not meet the requirements of dynamic conditions. In this paper, theDEM (Discrete Element Method) analysis software PFC3D was used to analysis thelateral pressure of silo, in both loading and unloading states. The author has donesome works as following:1. Building silo model by PFC3D software, then generate particles and make themfree fall under gravity to fill the whole container. Upon completion of this process,we can get the lateral pressure loading of this laden silo.2. By releasing the constraints at the discharge port, we can simulate the process ofsilo unloading. During the silo unloading process, we recorded the lateral pressureof silo wall. And we can obtain the maximum lateral pressures of different heightpositions. Comparing the dynamic analog value with calculation results and staticsimulation results, to analyze their difference.3. By analyzing the velocity vector in the process of unloading, we can determinethe flow patterns of material in the different periods are not the same. Accordingto the flow pattern and lateral pressure values, we can find the principle to theformation of maximum lateral pressure.4. Changing the silo discharge port diameter, funnel angle, internal friction andexternal friction, and analysis the impact of changes, we can find the relationshipbetween those parameters and maximum lateral pressure.The results show that during loading of the silo, the particles falling through thecorner part will lead to collide with each other. So the static lateral pressure resultingin greater the results calculated by the Janssen formula. By observing the velocity vector of stored material particle, we can see that the silo lateral pressure and thematerial flow patterns have a close relationship. During the unloading process, theflow pattern of material was switched from bodily movement into tubular flow orhopper flow. This type of flow exacerbated particles collide with each other, and alsocause to the appearing of the maximum lateral pressure, which is40%larger than thecalculated value. When changing the silo geometry and physical parameters, thematerial particles flow patterns will change, leading to lateral pressure changes.