| Granular materials are extremely common in nature and engineering,generally divided into powder and bulk.Silo is a container used to store various bulk materials.Now,due to the occurrence of silo accidents in various parts of the world,the safety of silo has received people's attention.It makes the study of the internal stress of the silo become the focus of research in various countries and regions.Among the existing theoretical calculation formulas of silo stress,the Janssen formula is the most classic,but this theoretical formula also only calculates the wall stress of a simple silo,and there is no theoretical calculation formula for the research on the wall stress of a complex structure.In response to this problem,based on the Jenike report of the wall stress of the purge bin of an enterprise,this article uses discrete element analysis software PFC to simulate the stress distribution of the bin,and then corrects the derived theoretical formula.The following work is completed for the design for reference.The PFC software was used to simulate the wall stress of the simple silo.After comparing with the results of Janssen's theoretical formula,the difference between PFC-2D and PFC-3D was analyzed.Then,PFC-2D was used to simulate the influence of various parameters on the wall stress distribution.The study found that PFC-2D is more suitable for qualitative analysis and PFC-3D is more suitable for quantitative analysis.The wall stress increases with the decrease of the internal friction coefficient of the particles and the wall friction coefficient,and also with the width of the outlet Decreases and increases,and increases with increasing cone inclination.The study found that PFC-2D is more suitable for qualitative analysis and PFC-3D is more suitable for quantitative analysis.The wall stress increases with the decrease of the internal friction coefficient of the particles and the wall friction coefficient,and also with the width of the outlet Decreases and increases,and increases with increasing cone inclination.Take the polyethylene product purge bin as an example to investigate the stress distribution in the silo with complex structure.Moreover,because the purge bin has a plurality of the internal flow cones at different heights,the structure is relatively complicated and the size is relatively large.Therefore,this article uses PFC-3D to carry out segmented simulation of the purge bin,respectively simulate the stress of the wall surface of each complex section of the bin,and finally synthesize the overall distribution map of the wall stress of the bin,and compare with the reported value of Jenike.The simulation results are consistent with the trend reported by Jenike,but there is a certain deviation,which is caused by the ratio of the diameter of the particles used in the simulation to the diameter of the purge bin is larger than the actual.Based on the Janssen hypothesis,the theoretical formulas of the wall stress of the straight cylinder and the internal flow cone section,the inverted cone and the internal flow cone section,and the inverted cone section are derived.PFC was used to analyze the influencing factors of the lateral pressure coefficient,and then the lateral pressure coefficient was modified.Based on the value reported by Jenike,the theoretical formula derived was corrected.A microscopic analysis of the interior of the silo is carried out.The particle size distribution of the particle size distribution system is generally larger,and it is generally larger than that of the particle size distribution system with uniform particle size.At the intersection of the straight cylinder and the inverted cone,the squeeze of the particles is more intense,which makes the void ratio smaller.The distribution of wall stress during unloading,particle velocity distribution,contact force network distribution,etc.are also analyzed.Through the work,it can conclude that the discrete element method and the revised Janssen theoretical formula can provide new ideas for the design of complex silos. |
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