A Study On Conduction Character Of Granular Materials

Granular materials are everywhere and in close relation to people’s daily life.However, granular materials are not one of the materials that we are quite familiar with，such as solids，liquids，and gases. Granular materials are an aggregation of a host of solidparticles that can move independently, and exhibit behaviors different from those ofnormal materials. Granular materials play an important role in people’s daily lives，andtheir phenomenons touch upon various fields，such as landslide、sandstorm in naturaldisasters，silo effect、traffic jam in social life，which makes the study of granularimportant.The mechanical properties of granular materials have been extensively studied in thecommunities of engineering and physics. The study of the electrical conductivity ofgranular material is in an emerging stage, and the conductive mechanism hasn’t beenexplained completely. The electrical conductivity of a granular system depends not onlyon the property of each individual particle but also on the contacting and mutualinteraction of them. Therefore, understanding the relationship between the mechanicaland conductive properties of granular materials is necessary.In this work, the electrical resistance of piled conductive grains is investigated byapplying external disturbing. Our experiments show that the disturbing strength, pilethickness and loading pressure have a significant influence on the pile electricalresistance. The pile resistance is found to be exponentially recovered from moment thatan impact disturbing is applied. On the other hand, the resistance increases linearly withpile thickness, while the proportionality coefficient shows complex dependence on theload. In addition, the pile resistance changes with the continuously loading in apower-law form, in which the power exponent b reduces with pile thickness. Discussionson the obtained experimental results are made by combining the resistance and thechanges of force chains induced by loading, and provide some clues for understandingthe force chain reorganization, force transmission, conductive mechanism in granularmaterials.