【Seminar】"Vertical pullout of a non-spherical intruder from a granular medium"

"Vertical pullout of a non-spherical intruder from a granular medium"
Dominik Krengel^a*, Jian Chen^b, Shun Nomura^a, Shunsuke Ota^a, Hidenori Takahashi^a
aTokyo University of Marine Science and Technology, Japan
^bJapan Agency for Marine-Earth Sciences and Technology, Japan

Intruder phenomena in granular media are common in geotechnical and engineering applications. Yet many questions remain unresolved: experiments cannot directly access the micromechanics of the granular material and intruder during motion; existing (semi-) analytical methods can usually predict only peak resistance based on assumed failure surfaces but not the force evolution; and most numerical studies are limited to spherical intruders or small displacement ranges because soil deformation during pullout causes stability issues.

In this work, we study the pullout of a plate intruder using a 2D polygonal Discrete Element Method, well beyond immediate failure from a quasi-static regime past the onset of granular flow. We show that peak resistance depends on the friction coefficient , but all cases collapse onto the same steady-state curve. After failure, the macroscopic fields reveal a conical structure forming above the plate, independent of ,  which determines the plate’s pullout resistance. The evolution of this effective intruder shape correlates with changes in most microscopic properties of the aggregate. In addition, shear zones at the plate edges act as natural hoppers, channeling material downward in discrete granular flows interrupted by jamming and arch formation.