An implicit integration algorithm for implementing the CASM model into the finite difference method analysis

Abstract This paper firstly presents an implementation of the unified critical state model for CLAY and SAND, i.e., CASM, into the finite difference method analysis platform FLAC3D, via the user defined constitutive models (UDM). The numerical implementation is performed with an implicit integration algorithm, and validation is conducted through a series of triaxial drained and undrained compression tests on normally consolidated clay, over-consolidated clay and sand. Application to an embankment loading is analyzed to demonstrate the efficiency and reliability of the proposed implementation of CASM model. Conclusions can be drawn that the algorithm exhibits high computational accuracy and efficiency, and has the ability to reasonably predict the stress-strain relationship of soil samples with varying consolidation degrees. Additionally, applications of the CASM model to geotechnical problems are widely expected for that the FLAC3D is better in dealing with convergence problems.