To simulate rainfall-induced slope failure in ABAQUS without using a subroutine, an indirect approach is required by modeling the effect of rainfall through pore pressure changes and soil property adjustments. The first step is to define the slope geometry and mesh, ensuring finer elements are used in the expected failure zone. The soil properties should be assigned using an appropriate constitutive model such as Mohr-Coulomb or Drucker-Prager, including parameters like cohesion, friction angle, density, Young’s modulus, and Poisson’s ratio.

After defining the material properties, an initial geostatic stress condition is applied by using gravity loading to establish in-situ equilibrium. This ensures that the slope is stable before the effects of rainfall infiltration are introduced. The rainfall effect is simulated through the application of time-dependent pore pressure boundary conditions. This can be achieved by increasing the pore pressure at the slope surface in a stepwise manner to represent infiltration while maintaining appropriate drainage conditions at the base.

A coupled pore pressure-displacement analysis is used to observe how the infiltration influences the slope stability over time. The permeability properties of the soil must be carefully defined, differentiating between saturated and unsaturated conditions to accurately model water flow. Strength reduction can be introduced by progressively reducing cohesion and the friction angle of the soil, allowing for the identification of the critical point at which slope failure occurs.

During post-processing, the results should be analyzed by monitoring pore pressure distribution, displacement contours, and shear strain localization to assess failure patterns. The factor of safety can be estimated using the strength reduction method by identifying the point of excessive displacement or large deformations. An alternative approach for advanced simulations is the use of the Coupled Eulerian-Lagrangian (CEL) method to capture rainfall-induced soil erosion, although this requires a more complex setup and computational effort.

By implementing these steps, it is possible to model the impact of rainfall on slope stability within ABAQUS without relying on user-defined subroutines.

Hello Dr. Mahip Singh thank you so much for your beautiful explanation. Can you please describe how are you going to model in CEL? Also if possible then share some documents/materials both for Abaqus Standard and CEL.