A numerical approach for the prediction of shear strength of stiff fissured clay samples based on direct shear tests and FLAC modelling

A model designated HSSM (homogenised strain softening model) was developed by using the experimental results, the initial numerical results obtained from the simulation of direct shear tests and FISH (FLACish) programming of the FLAG (Fast Lagrangian Analysis of Continual. This paper reports the stages and procedures applied to develop the HSSM and the application of the model for quantifying the interaction of some parameters together on the effective shear strength of the stiff fissured clay mass. In this model, the effect of each parameter such as width, spacing of fissures, preconsolidation pressure (p(c)'), OCR (overconsolidation ratio), horizontal locked in stress and size of the sample for a particular type of clay material were estimated. The effects of these parameters for any arbitrary set of input data las boundary conditions) were homogenised and applied as functions or coefficients to a base model for an unfissured over consolidated clay sample. The HSSM was verified by conducted tests and then was used to evaluate and predict the shear strength of cases which laboratory simulation was impossible and impractical. The obtained results, as well as the procedures applied in this study could give a good evaluation of the interaction of the parameters on the effective shear strength of a stiff fissured clay mass.