The history of PLAXIS: from Delft and the Delta Works to a global reference in numerical geotechnics

In geotechnical engineering there is a problem that sets soil apart from many other materials.

Soil is not simply:

force
↓
deformation

Its response depends on:

• confinement;
• stress history;
• drainage;
• pore pressure;
• time;
• construction sequence;
• load path;
• interaction with structures.

An excavation can be stable during one stage and fail during another.

A soft soil can keep settling for years.

A foundation can change the stress state of the ground in a profound way.

A deep excavation can move neighboring buildings.

And a tunnel cannot be understood independently of the soil that surrounds it.

PLAXIS was born precisely to study that kind of problem.

Its history begins in the Netherlands, in a country where understanding ground behavior has never been optional.

The Netherlands: engineering built around soil and water

A large part of the Netherlands sits on soft ground and at very low elevations.

Dutch engineering has spent centuries dealing with:

• dikes;
• compressible soils;
• consolidation;
• hydraulic works;
• stability;
• excavations;
• soil–water interaction.

During the twentieth century, works such as the Delta Works took those problems to an extraordinary scale.

Geotechnics needed tools that could go beyond simple analytical solutions.

1974: the roots of PLAXIS at Delft

Bentley places the start of the PLAXIS story in 1974, at Delft University of Technology.

Researchers began developing finite-element methods applied to geotechnical problems.

Early applications included work related to the huge storm-surge barrier at the Eastern Scheldt, part of the Delta Works.

This matters because PLAXIS was not born as a software product looking for a market.

It was born around real geotechnical problems.

The finite-element method enters geotechnics

The idea of FEM is to divide the domain into elements.

real soil
   ↓
mesh
   ↓
elements
   ↓
equations

In steel or concrete structures, that is already complex.

In soil an extra difficulty appears:

the material does not behave as a simple elastic solid.

That is why numerical geotechnics needs constitutive models.

What does PLAXIS mean?

The name comes from PLasticity AXISymmetry.

The first applications were closely tied to plasticity formulations and axisymmetric problems.

The name survived even when the program grew far beyond that origin.

1985: from research to a practical tool

According to the history published by Bentley, from 1985 PLAXIS began to change from a university tool into a product intended for professional use.

A particularly important collaboration took place with Rijkswaterstaat, the Dutch ministry responsible for infrastructure and water management.

The goal was clear:

turn a scientific code into something an engineer could use on real projects.

The PC revolution reaches geotechnics as well

At that time many FEM calculations required specialized machines.

Rijkswaterstaat pushed the development of a version that could run on personal computers.

By 1987 a first DOS version already existed.

Bentley also shows a historical image of PLAXIS 1.0 on DOS dated 1988.

That changed the accessibility of the tool in a profound way.

geotechnical FEM
before:
specialized computing

after:
PC

1993: PLAXIS leaves the university

In 1993, PLAXIS separated from the university environment and began to be developed as an independent company.

The project was no longer research alone.

It was becoming professional software.

Over the following decades PLAXIS would grow until it was used in:

• geotechnical consulting;
• universities;
• tunnels;
• mining;
• offshore;
• railways;
• skyscrapers;
• dams;
• dikes.

The big difference versus structural FEM

A general structural FEM program can represent:

nodes
elements
materials
loads

PLAXIS adds deeply geotechnical concepts.

For example:

soil layers
boreholes
phreatic levels
interfaces
staged construction
consolidation
groundwater flow
safety reduction

That domain knowledge is what makes it more than a general solver.

The real problem: modeling soil

In geotechnics, the result depends enormously on the constitutive model.

PLAXIS includes models from relatively simple to advanced.

Among the best known are:

Mohr-Coulomb

Useful as an initial approximation.

It uses parameters such as:

• E;
• ν;
• c;
• φ;
• ψ.

It is simple and robust, but it does not capture many real soil phenomena.

Hardening Soil

It represents nonlinear stiffness and hardening behavior with more realism.

It can distinguish stiffnesses related to:

• primary loading;
• unloading-reloading;
• oedometric behavior.

Hardening Soil Small-Strain

It adds small-strain stiffness behavior.

This can be fundamental for predicting movements around:

• excavations;
• tunnels;
• neighboring structures.

Soft Soil and Soft Soil Creep

Aimed at soft soils and problems where compressibility and time matter.

Staged Construction

Probably one of the most important concepts in PLAXIS is staged construction.

A geotechnical structure does not appear instantaneously.

Imagine an excavation.

Initial state
↓
excavate 2 m
↓
install support
↓
excavate 3 m
↓
install anchor
↓
excavate again
↓
build slab

Each phase changes:

• stresses;
• displacements;
• pore pressure;
• forces in elements.

PLAXIS can activate and deactivate:

• soil;
• structures;
• loads;
• interfaces;

by phases.

In many geotechnical problems:

the construction sequence is part of the physical problem.

Soil-Structure Interaction

A foundation does not work independently of the ground.

Neither does a wall.

PLAXIS can represent interfaces where soil and structure may:

• slide;
• separate;
• transmit forces.

Conceptually:

structure
↕
interface
↕
soil

This is especially important for:

• walls;
• piles;
• tunnels;
• foundations;
• sheet piles.

What is PLAXIS used for?

1. Deep excavations

One of its most classic applications.

It can study:

• wall displacements;
• ground movements;
• forces in struts;
• anchors;
• settlements of neighboring buildings.

2. Tunnels

It can represent:

• excavation;
• lining;
• rockbolts;
• shotcrete;
• ground pressure;
• interaction with buildings.

PLAXIS has specific tools for creating tunnel geometries.

3. Foundations

It can analyze:

• footings;
• slabs;
• piles;
• pile groups;
• offshore foundations.

The advantage of FEM is to study directly:

foundation
+
soil

as a system.

4. Embankments on soft soil

A classic geotechnical problem.

It can study:

• settlement;
• consolidation;
• stability;
• filling stages;
• inclusions;
• preloading.

5. Slopes

PLAXIS can run stability analyses through strength reduction.

Instead of using only classical limit-equilibrium methods, strength parameters are reduced progressively until numerical failure is reached.

6. Consolidation

When there is saturated soil and low permeability:

load
↓
excess pore pressure
↓
drainage over time
↓
increase in effective stresses
↓
settlement

PLAXIS can simulate this process.

7. Dynamics and earthquakes

Advanced versions can study:

• vibrations;
• seismic loads;
• ground response;
• dynamic interaction.

There are also specialized models for phenomena such as liquefaction.

8. Groundwater

Water is inseparable from geotechnics.

PLAXIS can include:

• phreatic levels;
• steady-state flow;
• transient flow;
• coupled flow-deformation.

This makes it possible to study how pore pressure and deformation interact.

PLAXIS 2D

PLAXIS 2D can represent problems through plane strain or axisymmetric formulations.

It is extremely useful when the problem has a sufficiently uniform geometry.

Examples:

• a long excavation;
• a typical embankment section;
• an idealized tunnel;
• a wall.

The advantage: lower computational cost.

PLAXIS 3D

Not every problem can be reduced to a 2D section.

PLAXIS 3D can represent:

• pile groups;
• irregular excavations;
• tunnels;
• buildings;
• edge effects;
• complex spatial geometry.

But the computational price is much higher.

This leads to an important rule:

using 3D because it “looks more real” does not mean it is necessary.

2018: Bentley buys PLAXIS

In 2018, Bentley Systems acquired PLAXIS.

The acquisition was part of a much larger strategy around the subsurface.

Bentley also acquired companies and technologies related to:

• SoilVision;
• Keynetix;
• later Seequent.

PLAXIS was no longer only inside an independent geotechnical company.

It now formed part of a global infrastructure platform.

2021: Seequent

In 2021, Bentley acquired Seequent, a company well known for geoscience software such as Leapfrog.

PLAXIS became increasingly integrated into this subsurface ecosystem.

The idea is to connect:

site investigation
↓
geological model
↓
geotechnical model
↓
FEM analysis

This makes a great deal of sense.

One of the largest historical problems in geotechnics is the separation between:

• field data;
• geological interpretation;
• analysis.

PLAXIS and Python

One of the most interesting modern features is its Python API.

Bentley allows automation of:

• model creation;
• phase definition;
• running calculations;
• extracting results.

Conceptually:

Python
↓
PLAXIS
↓
generate model
↓
calculate
↓
extract results
↓
compare scenarios

This changes the scale of the work a great deal.

Instead of running five scenarios by hand, a script can run hundreds.

PLAXIS and an AEC harness

This is especially interesting for agents.

A future workflow could be:

geotechnical investigation
↓
agent interprets parameters
↓
Python API
↓
PLAXIS
↓
calculate phases
↓
extract settlements
↓
QA/QC
↓
report

But there is an enormous caveat.

The agent should not freely decide:

• constitutive model;
• parameters;
• drainage;
• boundary conditions;

without technical supervision.

PLAXIS vs CalculiX

Both use FEM.

But they are aimed at different problems.

CalculiX

More general and mechanical:

stress
strain
contact
solid mechanics

PLAXIS

Deeply geotechnical:

soil models
groundwater
construction stages
consolidation
soil-structure interaction

If the problem is a steel base plate:

CalculiX

may make more sense.

If the problem is how that foundation interacts with 30 m of soil:

PLAXIS

enters its natural territory.

PLAXIS vs GeoStudio

They are different as well.

GeoStudio has extremely strong tools for problems such as:

• seepage;
• slope stability;
• geotechnical environmental modeling.

PLAXIS is more centered on stress-strain FEM.

In fact, Bentley/Seequent now offer them inside a complementary ecosystem.

The danger of a pretty FEM image

PLAXIS produces impressive visualizations.

Contours.

Deformations.

Plastic points.

Vectors.

But a colorful image does not prove that the model is correct.

Serious errors can come from:

• uncalibrated parameters;
• the wrong constitutive model;
• boundary conditions;
• mesh;
• incorrect drainage;
• an unrealistic construction sequence.

In geotechnics there is an additional problem:

real soil is never fully known.

2026: PLAXIS today

Today PLAXIS is sold mainly as:

• PLAXIS 2D;
• PLAXIS 3D;

with different capability levels.

Current versions may include, depending on tier:

• consolidation;
• dynamics;
• groundwater;
• coupled flow-deformation;
• thermal effects;
• Python automation;
• multicore solvers;
• IFC/CAD interoperability.

PLAXIS remains commercial software.

Bentley’s current page shows PLAXIS 3D from about USD 11,675 per year on certain plans and in certain regions, with higher tiers considerably more expensive.

That also explains why open-source alternatives remain relevant.

Timeline in brief

1974
TU Delft
geotechnical FEM research
        ↓
Delta Works
        ↓
1985
shift toward practical software
        ↓
Rijkswaterstaat
        ↓
1987–1988
PLAXIS for DOS / PC
        ↓
1993
PLAXIS becomes independent
        ↓
PLAXIS 2D
        ↓
PLAXIS 3D
        ↓
advanced constitutive models
groundwater
dynamics
automation
        ↓
2018
Bentley acquires PLAXIS
        ↓
2021
Bentley acquires Seequent
        ↓
subsurface ecosystem
        ↓
2026
PLAXIS + Python + BIM/geology integration

Conclusion

PLAXIS was born from a deeply Dutch need:

to understand how to build safely on and inside the ground.

It started as research at Delft.

It was applied to the challenges of large hydraulic works.

It moved to the PC.

It became a company.

It expanded its constitutive models.

It added 3D, consolidation, groundwater, dynamics, and automation.

And it finally ended up inside the geotechnical and geological ecosystem of Bentley and Seequent.

But its most important contribution remains conceptual:

treat the ground, the structure, the water, and the construction sequence as parts of the same numerical system.

And that way of thinking is fundamental to modern geotechnical engineering.

References

1. Bentley Systems. Solid Ground: Bentley’s PLAXIS Software is Changing the World.
2. Bentley Systems. PLAXIS 2D.
3. Bentley Systems. PLAXIS 3D.
4. Bentley Systems. Company History.
5. Bentley Systems. PLAXIS 2D Product Data Sheet.
6. Bentley Systems. PLAXIS 3D Product Tiers.

Evaluation and limitations

Treat the notes below as evaluation context, not as a verified calculation or code check.

Use it for 2D/3D geotechnical FEM: excavations, tunnels, foundations, consolidation, dynamics, and soil–structure interaction. Construction sequence is part of the physical problem. Do not use 3D only because it looks more real.