Granular plasticity control from subtle changes in microstructure geometry: the fine grain infiltration technique
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The mechanical behavior of granular materials at the macroscale arises from both local physical interactions between grains and geometric effects. When considering widely graded materials that mix fine and coarse grains, these grains can self-organize into various patterns that influence macroscopic behavior depending on the fine-grain content. In underfilled conditions [1], fine grains are primarily located in the voids between the coarse skeleton. Although they do not directly bear stresses, these fine grains can stabilize force chains, which, at the macroscale, influence the plastic behavior of granular materials by altering the direction of the non-associated flow rule and modifying the hardening law [2,3]. This work demonstrates how this property can be used to control the plastic behavior of granular materials by adding a small amount of fine grains to an initially loose material that is sensitive to static liquefaction. Both experimental and numerical results show that it is possible to mitigate the risk of static liquefaction by infiltrating a very limited amount of fine grains, as indicated by the mechanical response of infiltrated materials with a fine content of less than 5% by mass. This drastic change in mechanical response results from the clogging of fine grains in strategic locations around the contact points between coarse grains. This microscopic interpretation is further supported by analyzing the mechanical response of reconstituted samples with similar fine contents. Adding fine grains between coarse grains or allowing them to float in the voids does not prevent static liquefaction from occurring.