Rock shear creep modelling: DEM – Rate process theory approach

Understanding the rock creep behavior is necessary to determine the long-term strength and safety of several geotechnical designs. There are several formulations to study the rock creep; however, most of them do not properly capture the tertiary creep. To overcome such limitation, model improvements have been made and new creep models (e.g., creep models with an associated viscoplastic flow rule) have been proposed. As an alternative, the Rate Process Theory (RPT) has been recently used to study the soil/rock creep behavior. This article expands previous works by analyzing the applicability of the Discrete Element Method (DEM) with RPT implementation to simulate Rock Shear Creep (RSC). To do that, (i) 2D DEM direct shear creep tests under Constant Normal Load (CNL) conditions are used, (ii) DEM specimens are built by a combination of the Flat-Joint Contact Model (FJCM) and the Linear Model (LM), and (iii) the DEM + RPT approach is calibrated by using experimental tests from the literature. DEM results presented here illustrate the suitability of DEM–RPT methodology to reproduce all stages of RSC, including tertiary creep. The effect of the applied shear stress and normal stress on RCS is also analyzed. Finally, the most important novelties of this paper are: (1) the DEM–RPT methodology can be easily calibrated by using a laboratory direct shear creep test; (2) the calibrated DEM models are suitable to analyze the main aspects of RSC; and (3) DEM results qualitatively agree with the overall experimental trend published in the literature.