Elastoplastic-damage-seepage coupling model and numerical algorithm for rock slope stability evaluation

The stability of slope under complex geological conditions is one of the essential issues in geotechnical engineering. The mechanical damage caused by external force load and the hydraulic property of rock have both significant influences on slope stability. However, the two factors and the coupling process between them are not considered in the traditional slope safety calculation method. Firstly, in this paper, an elastoplastic-damage-seepage coupling model is established based on the modified Mohr-Coulomb (M-C) criterion. This model takes into account the weakening effect of damage on the strength of rock mass. Further, according to the Biot's theory and the evolution equation of permeability coefficient, a complete hydraulic-mechanics (HM) coupling model is established. Secondly, the fully implicit backward Euler algorithm and "strict-cornered" algorithm are used to integrate the stress precisely. The complete coupling analysis of HM is implemented by the step-by-step iterative method. By combining the centrifugal loading method (CLM) with the FEM program, the factor of slope safety (FOS) under the coupling influence of damage-seepage can be solved. The calculation results showed that, compared with the traditional rounded M-C model, the results obtained by the "strict-cornered" algorithm method in this paper are closer to the theoretical solution. The solution process is robust with a global second-order convergence rate. After considering the effects of damage and seepage, the FOS is obviously reduced. Finally, the model is applied to the stability evaluation of an actual engineering. The variation rules of pore water pressure, displacement field, damage zone and FOS are calculated under different head heights. The model built in this paper considers the coupling characteristics of rock seepage-stress-damage well. The proposed numerical algorithm ensures the accuracy and rationality of the calculation results which provides a theoretical foundation for engineering application.