Numerical Modeling of Experimental Rock Friction Data for Rough Surfaces

Date: 4/25/2019

Time: 11:45 AM

Room: Elliott Bay

There is experimental evidence that frictional sliding along a non-planar surface depends on its roughness, with more stable slip for rougher surfaces. Here we design a numerical scheme to reproduce such experimental data and analyze the mechanisms governing this behavior. We model numerically the tri-axial stick-slip experiments performed by Goebel et al. (2017) on pre-fractured and roughened pre-cut Westerly granite samples, using an idealized 2-D model. Our numerical approach includes four main features: (1) To enable slip that is large relative to the size of the elements near the fault, friction laws are implemented into the mortar finite element method, in which non-matching meshes are allowed across the fault and the contacts are continuously updated; (2) To accurately represent the fault geometry, the mesh is refined near the fault with hanging nodes; (3) To model a sequence of slip events, the method uses variable time steps with quasi-static and fully dynamic schemes; and (4) Using implicit return mapping algorithm, the bulk is modeled with Drucker–Prager viscoplastic rheology. We assume that the rough interfaces are governed by a combined rate and state and enhanced dynamic weakening friction law and search for a set of frictional parameters on the interfaces that give frictional behaviors, integrated for the whole model, similar to that observed in the experiments. The model captures the transition between slow slip and fast slip events observed in the experiments for different amplitudes of roughness, as well as the corresponding static stress drops.

Presenting Author: Yuval Tal

Authors