Plaxis 2d 8.6 Updated May 2026
Long Report: PLAXIS 2D Version 8.6 – Capabilities, Applications, and Technical Overview
Part 3: The 8.6 “Trick” — and the Manual
Frustrated, she remembered a nuance of PLAXIS 2D 8.6: Undrained A uses effective strength parameters but enforces undrained Poisson’s ratio and bulk stiffness. However, for soft clays, the Undrained (B) option — using undrained shear strength directly — was safer. Also, version 8.6 lacked the later Undrained (C) and full coupled flow-deformation, but it had an advanced feature: corrected undrained stiffness via the Unloading/Reloading stiffness ( E_ur ) in Hardening Soil.
She tweaked the model:
- Undrained B, ( S_u ) profile from field vane.
- Used ( E_ur = 3 \times E_50^ref ) (a known 8.6 best practice for excavation).
- Reduced the mesh coarseness near the wall — 8.6 could refine locally, but too many elements crashed the solver. She kept it reasonable.
Final result: 22 mm deflection — plausible, safe, and close to field measurements from a nearby project.
Migration Path: Moving from 8.6 to Plaxis 2D CE V20+
If your organization is still running 8.6, consider a migration strategy: plaxis 2d 8.6
- Step 1: Export geometry using the DXF or TXT format.
- Step 2: Verify material parameters, especially for the HSsmall model (the small-strain parameters
G0andγ0.7have been refined in newer versions). - Step 3: Re-run key benchmark cases (e.g., a simple footing or sheet pile) to calibrate differences.
Bentley provides a migration utility, but manual verification remains essential.
3.1 Graphical User Interface (GUI)
Unlike the modern CONNECT Edition, v8.6 utilizes a structured menu system rather than a Ribbon interface. It separates the workflow into distinct modes:
- Input Mode: For geometry creation, mesh generation, and material property assignment.
- Calculations Mode: For defining calculation phases (plastic, consolidation, safety).
- Output Mode: For visualizing displacements, stresses, and structural forces.
8. File Structure and Extensions (Version 8.6)
| File type | Extension | Description |
|-----------|-----------|-------------|
| Input project | .p2d | Binary main file (geometry, materials, loads) |
| Calculation results | .plx | Binary output (states per phase) |
| Mesh file | .msh | Generated mesh storage |
| Output selection | .slt | Saved points/cross-sections |
| Hardening Soil temp | .dat | Temporary data | Long Report: PLAXIS 2D Version 8
Note: Version 8.6 binary files cannot be opened directly in modern PLAXIS 2D (after Version 9). Migration requires export/import via DXF geometry and manual redefinition of materials.
Final Recommendation
Use PLAXIS 2D 8.6 if:
- You are a student learning the basics of Finite Element Method (FEM). The lack of complex buttons helps you focus on the soil mechanics and mechanics of deformation.
- You need to verify an old report or run a simple slope stability/check that does not require advanced constitutive modeling.
- You have an older computer or operating system.
Avoid PLAXIS 2D 8.6 if:
- You are performing high-stakes commercial design requiring advanced soil models (like Small Strain stiffness).
- You need to automate calculations (modern versions use Python scripting).
- You require high-quality graphical output for client presentations.
Rating: 7/10 (In the context of its time, it was a 9.5/10. Today, it remains a reliable educational tool but is obsolete for advanced commercial application).
2. The Workflow: A Deep Excavation Case Study
Let’s model a 10-meter excavation supported by a concrete diaphragm wall.