Initial guidelines for the selection of input parameters for cohesion-weakening-friction-strengthening (CWFS) analysis of excavations in brittle rock

Abstract

Recent studies on the behaviour of brittle rock under high stress around excavations have found that the use of a cohesion-weakening-friction-strengthening (CWFS) strength criterion in continuum models has provided excellent agreement with observations made in-situ, including fracture zone size, fracture zone shape, and ground displacement magnitudes. Despite continued success in the application of this strength model for brittle rock, the lack of rigorously established guidelines for CWFS model input parameter selection have limited the use of this approach. In this study, a review of published case studies using the CWFS strength models is provided, and parametric relationships are examined based on the most reliable data sets. Each model parameter is considered individually, and guidelines for parameter selection are provided. In addition, the process of numerical back analysis using the CWFS is discussed and a proposed back analysis methodology is outlined. The use of these guidelines, along with the suggested back analysis approach, will allow for an easier and more effective implementation of the CWFS strength model for numerical modelling of future case studies on brittle rock damage around highly stressed excavations.