Improved friction force calculation with an augmented open-close iteration formulation in discontinuous deformation analysis

Abstract

In applying discrete numerical methods to model large-displacement problems, such as rockslides, accurate contact force calculation requires correct representation of the evolving contact status. In the discontinuous deformation analysis (DDA), open-close iteration (OCI) serves the crucial role of ascertaining that contact status is properly updated throughout an assembly of discrete blocky elements. OCI is a simple, straightforward and intuitive procedure but has shortcomings that affect analysis accuracy. Alternatives are generally computationally involved and have other issues, and OCI with its large installed base can still be one of the most desirable ways to track contact state with proper improvements. This is exactly this study aims to achieve. This study proposes an augmented open-close iteration (AOCI) algorithm that amends the shortcomings of OCI through: (1) it enhances the modeling of transition between contact states; (2) it provides the control mechanism for improving shear forces and shear movement direction also during OCI iteration. The AOCI is easy to add to the existing structure of OCI. The improved performance of AOCI over the traditional approach is demonstrated using both static and dynamic test cases.