DLO - A revolutionary new technology

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 engineering analysis.

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 stability analysis.

The DLO method is underpinned by rigorous theory, published recently in the Proceedings of the Royal Society.

Verification

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.

*The other common traditional analysis approach is the classic 'Rankine' style approach. At sufficent levels of precision this approach gives results that are little distinguishable from the 'Coulomb' approach and identical in many cases.

A similarity with string art!

DLO works by finding the layout of slip-lines (or 'discontinuities') at collapse. Conceptually it can be likened to string art: a regular grid of pegs is laid out across the problem domain, and the string linking any pair of pegs represents a slip-line within the soil - except here the network of lines is chosen by the software rather the artist, and link together so as to describe the form of the critical collapse mechanism. Increasing the number of pegs increases the accuracy of the solution and, using modern computing power, the optimal mechanism can be selected from billions of different layouts of failure lines.