How DLO works
- Nodes are distributed across the domain (a and b).
- Potential slip-line discontinuities connect the nodes (c).
- Optimization is used to identify the slip-line discontinuities that make up the critical collapse mechanism (d).
- The corresponding collapse load factor is found.
Steps in the DLO procedure: (a) starting problem (surcharge close to a vertical cut); (b) discretisation of soil using nodes; (c) interconnection of nodes with potential discontinuities; (d) identification of critical subset of potential discontinuities using optimisation (giving the critical failure mechanism).
Benefits of DLO
- No need to independently account for different failure modes - all possible cases are simultaneously considered.
- Can be applied to standard and non-standard problems alike.
- Handle uncertain ground conditions by modelling multiple soil types in a single soil body (the critical case is always found).
- Automatically identify the critical configuration of any number of sliding soil blocks at failure.
- Provides an immensely powerful 'one stop shop' stability analysis tool.
- Easily set up a model, solve, then visualize and check the resulting failure mechanism.
- Complements the trend of design codes to move towards a generic Limit State Design methodology (e.g. Eurocode 7)
- Underpinned by rigorous theory published in the Proceedings of the Royal Society.
LimitState:GEO - One product, many applications
- Full on-screen control over problem geometry.
- Wizards for rapid definition of standard problem types - (see the application notes).
- A library of predefined Eurocode partial factor sets (and the ability to define others).
- Ability to analyse reinforced earth structures (e.g. slopes with soil nails - watch movie).
- Easily specify a groundwater table (horizontal or variably inclined - watch movie).
- Make quick changes and explore a variety of 'what if?' scenarios (watch movie).
- Animate failure mechanisms and view problems in 3D.
- View stress distributions on solid bodies (watch movie).
- Free-body diagrams provide a clear and easy means of checking both input and solution validity.
- Clear and comprehensive report output.
- Solutions verified against known limit analysis solutions.
Shallow learning curve
- Easier to use than other generally applicable tools (e.g. non-linear finite elements) or single application products.
- Adjust the model on screen to make quick and simple modifications to geometry, boundary conditions, materials and loading.
- Import geometries from CAD.
Full support for Eurocode 7
- Built-in Eurocode 7 partial factor sets.
- Use favourable or unfavourable loading and be alerted if this is incorrect for the critical mechanism.
- Define and solve for many scenarios in one go (e.g. EC7 Design Combinations 1 & 2, drained and undrained cases).
At present geotechnical engineers often assess the stability of slopes,
foundations and walls using traditional ultimate limit state analysis
techniques. Each technique is generally suitable for just one standard problem
type, and typically assumes failure involving just a few sliding blocks
of soil (e.g. 'method of slices' or 'Coulomb wedge' analysis)*. However solving
non-standard problems is often challenging, with the complex
mathematics involved making hand analysis arduous, and unsuitable to routine
LimitState:GEO utilizes something new - Discontinuity Layout Optimization (DLO).
This automatically identifies the critical configuration of sliding
soil blocks at failure and can be applied to standard and non-standard problems
alike, giving the engineer an immensely powerful 'one stop shop'
stability analysis tool with the ability to easily set up a model, solve, then
visualise and check the resulting failure mechanism.
With DLO there is no need to independently consider different failure modes e.g.
the sliding or bearing collapse of a gravity wall. All possible
modes, (anticipated or not anticipated by the engineer) are simultaneously
considered thus significantly reducing the time required to undertake a
The DLO method is underpinned by rigorous theory, published recently in the
Proceedings of the Royal Society. For details, see here.
*The other common traditional analysis approach is the classic 'Rankine' style
approach. At sufficient levels of precision this approach gives results
that are little distinguishable from the 'Coulomb' approach and identical in
One product - many applications
* Fully flexible control over problem geometry and ground profile
* Also has built in 'wizards' for rapid definition of a wide range of
standard problems including:
o slope stability analysis
o foundation bearing capacity analysis
o retaining wall analysis
* Ships with a library of predefined Eurocode partial factor sets; however,
the user can define (and save) an unlimited number of their own
partial factor sets
* Analyse reinforced earth structures (e.g. slopes with soil nails)
* Groundwater table (horizontal or variably inclined) easily specified
Shallow learning curve
* Easier to use than most ‘single application’ products
* Quick and simple modifications to geometry, boundary conditions, materials
and loading, using mouse or keyboard
* Import geometries from CAD (dxf)
* Much, much easier to use than other generally applicable tools, e.g.
non-linear finite elements
* Comprehensive user manual
Output that is easy to verify and understand
* Generates simple free-body diagrams which provide a clear and easy means
of checking solution validity
* Visualise failure modes easily (animation & 3D view)
* Clear yet comprehensive report output
Full support for Eurocode 7
* Built-in Eurocode 7 partial factor sets
* Specify favourable or unfavourable loading and be alerted following
analysis if this is incorrect for the critical mechanism.
* Use the Scenario manager to define and solve multiple scenarios in one go
(e.g. EC7 Design Combinations 1 & 2, drained and undrained cases etc.
A Revolutionary solver engine
* Harnesses the power of the groundbreaking ‘Discontinuity Layout
* Fully flexible ultimate limit state analysis tool
* Finds the true failure mechanism for any problem - not one e.g. based on
prescribed circles, slices or wedges
* Handle uncertain ground conditions by modelling multiple soil types in a
single soil body (LimitState:GEO will always pick the critical case)
Unlike most other state-of-the-art analysis tools, output from LimitState:GEO is remarkably easy to check. The software can output a free body diagram for each sliding block - complete with force equilibrium equations which are straightforward to check by hand, ensuring no error has been made in setting up the problem. To see a list of tests carried out using LimitState:GEO to verify its accuracy against known limit analysis solutions, visit the verification pages.