Dataset for "Frictional Response of Fault Gouge Analogs to Normal Stress Perturbations: Implications for the Microscopic Origin of Rate- and State-Dependent Friction Evolution"

Description

This repository contains the LAMMPS input files and processed numerical data used in the study “Frictional Response of Fault Gouge Analogs to Normal Stress Perturbations: Implications for the Microscopic Origin of Rate- and State-Dependent Friction Evolution”. Normal stress perturbations strongly modulate fault strength and slip behavior. Non-isobaric Rate- and State-Dependent Friction (RSF) laws are widely used to describe frictional responses, yet their applicability and micromechanical origins remain poorly constrained. Using discrete element modeling, we examine the normal stress step responses of quartz and clay analogs with contrasting strength and slip stability, and relate their macroscopic RSF-like behavior to micromechanical processes. The global response agrees with available experiments. Normal stress steps induce a three-stage shear stress response, with an initial linear increase followed by a quasi-exponential rise toward a new steady state. The nonlinear stage of the shear response is slip dependent rather than time dependent, which we interpret in terms of a nearly velocity-independent strain scale over which the contact fabric loses memory. For normal stresses (5–25 MPa), loading velocity (0.0003–1 m/s), and normalized loading stiffness (0.0005–0.009 1/μm), non-isobaric RSF laws broadly capture the shear stress response, with the Slip law underestimating the linear stage and the Aging law overestimating the nonlinear stage. This mismatch reflects a transition from Aging-law-like to Slip-law-like behavior during transients. At steady state, the state variable serves as an effective proxy for contact area, but it does not during transients, even though contact-area evolution more closely resembles the Aging-law state. The RSF parameter \alpha, which describes the normalized nonlinear shear response, is controlled by the macroscopic friction coefficient and particle size distribution. These results provide new insight into the micromechanical mechanisms underlying shear responses and RSF behavior under normal stress perturbations.

Institutions

• Tongji University

  Shanghai, Shanghai
• Purdue University West Lafayette

  Indiana, West Lafayette

Categories

Funders

• National Key Research and Development Plan of China

  Grant ID: 2025YFE0125500
• National Natural Science Foundation of China

  Grant ID: 42477141
• Collaborative Research Project under International Joint Research Laboratory of Earthquake Engineering (ILEE)

Licence