Validation of a Continuum-based Weak Zone Joint Model for Simulating Anisotropic Rock Mass Strength

Abstract

In recent decades, the approach to estimating rock mass strength and its anisotropic behaviour more accurately has been a growing topic of interest in the rock mechanics community. To evaluate jointed rock mass behaviour more accurately, sophisticated modelling techniques such as Synthetic Rock Mass (SRM) models are becoming increasingly popular. Still, these methods are computationally intensive and require detailed site characterization data that are often unavailable during the initial stages of project development and are not always the most practical option. This study developed an alternative continuum-based SRM-like model where thin contiguous regions of weak continuum material with equivalent joint properties are in place of explicit interface joint elements. The finite-difference program FLAC used these weak zone joints (WZJ) to generate a jointed rock mass continuum model (JRCM). The JRCM concept was applied to systematic sets of persistent joints, a single non-persistent joint, and two intersecting joints to validate the practicality of using WZJ. Results found that the concept produced reasonable anisotropic rock mass strength estimates for most cases, with some limitations. The model captured the anisotropic behaviour while reducing time requirements to develop and recalibrate a conventional SRM. The JRCM concept demonstrates a practical alternative to estimating anisotropic rock mass strength for specific projects where the quantity or quality of data is limited. Furthermore, the reduced run times could allow multiple iterations to perform a probabilistic assessment of the rock mass strength.