A New Integrated Energy-Based Approach for the Stability Analysis of Mixed Soil-Rock Slopes: The MIST3D Method

The stability analysis of mixed soil-rock slopes represents a paramount challenge in computational geomechanics due to the complex interplay between the non-linear plastic behavior of loose soil mantles and the structural dominance of fractured rock masses. Traditional 2D Limit Equilibrium Methods (LEM) often fail to capture these interactions, as they rely on predefined slip surface geometries and simplified material schematizations. This paper introduces MIST3D, a novel integrated framework that employs a variational energy functional approach to evaluate slope stability. By utilizing 3D multi-domain modeling and a hybrid evolutionary search algorithm — combining Genetic Algorithms with Particle Swarm Optimization — the method automatically identifies kinematically admissible but non-obvious failure mechanisms. MIST3D facilitates a seamless transition between drained and undrained states via a time-dependent exponential decay function and incorporates a pseudodynamic seismic extension that treats inertial demand as a volumetric energy component. Validation against standard LEM results demonstrates that MIST3D identifies more critical failure states by accurately capturing 3D effects and composite surfaces that "refract" at geomechanical interfaces.