Description
The compression cap currently lacks a realistic hardening formulation. To properly represent volumetric compaction under high compressive stresses, the cap requires an exponential hardening model, consistent with established geotechnical practice.
As a reference, PLAXIS cap-based models (e.g. Hardening Soil family) use exponential-type evolution laws for the cap/preconsolidation pressure as a function of plastic volumetric strain. This issue proposes to investigate the hardening formulation used in PLAXIS and implement a corresponding exponential hardening model for the compression cap in the GeoMechanicsApplication.
Investigate cap hardening in PLAXIS
Identify which hardening law(s) are applied to the compression cap (e.g. exponential evolution of preconsolidation stress with plastic volumetric strain).
Clarify required parameters and sign conventions (compression positive).
Implement exponential hardening model
Add an exponential hardening law for the compression cap (e.g. evolution of preconsolidation stress / cap position).
Integrate it into the existing cap return‑mapping framework.
Ensure hardening is driven by accumulated plastic volumetric strain from cap yielding only.
Unit testing
Add unit tests that:
- Verify cap expansion under isotropic compression.
- Confirm exponential evolution (non‑linear growth) of the cap parameter.
- Ensure no hardening occurs when the cap is inactive or disabled.
- Preserve existing behavior when cap hardening is off.
Documentation
Extend README_cap.md
Description
The compression cap currently lacks a realistic hardening formulation. To properly represent volumetric compaction under high compressive stresses, the cap requires an exponential hardening model, consistent with established geotechnical practice.
As a reference, PLAXIS cap-based models (e.g. Hardening Soil family) use exponential-type evolution laws for the cap/preconsolidation pressure as a function of plastic volumetric strain. This issue proposes to investigate the hardening formulation used in PLAXIS and implement a corresponding exponential hardening model for the compression cap in the GeoMechanicsApplication.
Investigate cap hardening in PLAXIS
Identify which hardening law(s) are applied to the compression cap (e.g. exponential evolution of preconsolidation stress with plastic volumetric strain).
Clarify required parameters and sign conventions (compression positive).
Implement exponential hardening model
Add an exponential hardening law for the compression cap (e.g. evolution of preconsolidation stress / cap position).
Integrate it into the existing cap return‑mapping framework.
Ensure hardening is driven by accumulated plastic volumetric strain from cap yielding only.
Unit testing
Add unit tests that:
Documentation
Extend README_cap.md