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A model of sheared gouge layer with thermally varying material properties

Ahmed Elbanna (University of Illinois (UC)), Jean Carlson (UC Santa Barbara)

Multiscale Mechanics of Particulate Media

Mon 4:20 - 5:40

Sayles 105

We present a model of sheared dry granular materials based on the shear transformation zone (STZ) theory. This is a statistical-physics based theory for modeling plastic strain accumulation in amorphous materials due to the non-affine irreversible local granular rearrangements. We extend the Lieou-Langer STZ framework [Lieou and Langer, Phys. Rev. E 85, 061308 (2012)] to account for cohesive interactions and the thermal dependence of the material properties of the constituent particles. To derive a cohesive law that is appropriate for incorporation in meso- and macro-scale fracture models, we solve a set of differential equations describing the evolution of the state variables characterizing the sheared system. The resulting law is effectively a slip-slip rate-dependent Mode II cohesive law. We discuss the predictions of our model within the context of shearing a thin gouge layer (~1cm) under earthquake-like condition. The model shows that at small strain rates, the steady state sliding shear stress depends weakly on strain rate. As the strain rate approaches a critical value, the steady state sliding shear stress shows strong strain rate dependence. The model is also capable of predicting shear banding instability which has a profound effect on the resulting stress strain response and consequently on the macrosocpic fracture behavior. We discuss the implications of our results for understanding gouge friction in the context of earthquake ruptures.