Load Advancement Procedure Failure (Error Code: 103)

In Plaxis, the Load Advancement Procedure Failure (Error Code: 103) typically occurs during a structural analysis or stress analysis when the program cannot converge to a solution due to numerical or physical issues in the model. This error can be caused by a variety of factors, including inappropriate boundary conditions, material properties, or other modeling issues.

Here are some common causes for Error Code: 103 (Load Advancement Procedure Fails) and how you can address them:

Common Causes of Load Advancement Procedure Failures: #

  1. Non-Converging Material Models:
    • Certain material models (e.g., softening materials, undrained soils, or models with a high degree of non-linearity) may not be stable for the chosen load increments or boundary conditions.
    • Solution: Check that the material properties are reasonable and adjust the settings, such as the strength parameters, modulus, or plasticity settings to ensure they are within realistic ranges.
  2. Too Large Load Increment:
    • If the applied load increments are too large, the solution may fail to converge due to instability, especially in highly nonlinear models.
    • Solution: Reduce the load increment size. For example, if you are applying pressure or a force, reduce the initial load step or use smaller increments to allow the solver to better capture the changes in behavior.
  3. Improper Boundary Conditions:
    • Incorrectly applied boundary conditions or constraints (e.g., over-constraining the model or unrealistic boundary setups) can lead to failure to find a solution.
    • Solution: Review the boundary conditions to ensure that they reflect the physical problem. For example, avoid excessive or unrealistic restraints, especially for models involving large deformations.
  4. Excessive Initial Deformations:
    • If the model starts with large initial deformations or unrealistic initial stresses, the solver might fail to progress due to numerical instability.
    • Solution: Use the initial stress calculation or recheck the model's initial configuration to make sure it starts from a reasonable state (e.g., no extreme displacements).
  5. Inconsistent Mesh:
    • A poorly defined or overly coarse mesh can result in inaccuracies, leading to convergence issues. In some cases, a mesh with overly sharp angles or large elements in areas with high stress gradients may cause the solver to fail.
    • Solution: Refine the mesh in critical areas or use higher-order elements (e.g., quadratic elements) to improve the mesh quality and ensure smoother behavior under load.
  6. Incorrect Contact or Interaction Definitions:
    • If you're using contact interfaces between different materials (e.g., between soil and structures, or between geogrids and soil), improper contact definitions (such as too stiff or incorrect friction properties) can cause convergence issues.
    • Solution: Ensure that contact properties (e.g., friction, cohesion, and dilatancy) are properly defined and realistic. You may also need to refine the contact zone in critical areas.
  7. Soil-Structure Interaction Problems:
    • When modeling interactions between soil and structures (such as piles, foundations, or geogrids), misbehavior in the interaction (e.g., overly rigid structures, poorly defined interactions) may lead to the error.
    • Solution: Recheck the material properties for both the soil and the structure and make sure that the interaction is well defined.
  8. Solver Settings:
    • Sometimes the failure is related to solver settings, especially if the chosen solution method is not appropriate for the type of analysis.
    • Solution: Consider switching the solver type (e.g., from automatic to incremental or non-linear solvers) or adjust solver parameters like convergence tolerance and iteration limits.

Steps to Troubleshoot: #

  1. Check Load Steps and Convergence Criteria: Start by reducing the load step size, and ensure that the solver convergence criteria are not too strict.
  2. Examine Material Properties and Boundary Conditions: Review your material models and boundary conditions for unrealistic or inconsistent settings.
  3. Refine the Mesh: If you have a coarse mesh, refine it in regions of interest, especially where you expect high deformation or stress gradients.
  4. Initial Stress Analysis: Perform an initial stress analysis to ensure that the model starts with a realistic configuration.

Conclusion: #

Error Code 103 can stem from a variety of issues, but it typically points to numerical or physical modeling inconsistencies. Start by checking your material models, boundary conditions, load increments, and mesh quality, and adjust accordingly. Reducing the load step and improving the model's numerical stability should help resolve the issue.