20/05/2008 LimitState:GEO launch & technology briefing - ICE London 04/06/2014geo1.0 LimitState:GEO Launch event & technology briefing 20 May ICE London Matthew Gilbert BEng PhD CEng MICE Managing Director, LimitState Ltd Colin Smith MA(Cantab) PhD Director & LimitState:GEO Product Manager, LimitState Ltd

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Programme 1.Introduction to LimitState 2.LimitState:GEO & how it works 3.Verification Coffee break Practical Case Study 5.Design to Eurocode 7 6.Closing remarks

20/05/2008 LimitState:GEO launch & technology briefing - ICE London 04/06/2014 geo1.0 Introduction to LimitState

20/05/2008 LimitState:GEO launch & technology briefing - ICE London About LimitState Striving to: –Provide engineers with an unrivalled suite of fully supported software for ultimate limit state analysis & design –Take full advantage of state-of-the-art algorithms & optimization technology –Ensure applications have industry leading levels of ease of use –Strong emphasis on robustness and extensive validation

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Current Product - LimitState:RING Rapid analysis software for masonry arch bridges Launched May 2007 Builds on research software already used in >40 countries Clients include:

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Current Product - LimitState:RING For more details visit: Or attend a LimitState:RING seminar: –May 21 st London (IStructE) –June 4 th Glasgow –June 25 th Dublin (see website for details)

20/05/2008 LimitState:GEO launch & technology briefing - ICE London 04/06/2014 geo1.0 LimitState:GEO

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Context Traditional stability analysis techniques are not serving geotechnical engineers well enough! –Single application programs E.g. for slope stability; retaining walls etc Often not very easy to use; engineers need to learn how to use several programs; each has very narrow applicability –Complex numerical analysis programs E.g. based on non-linear finite element Powerful and flexible but numerous input parameters; careful tuning needed to avoid numerical stability problems; arguably too cumbersome for routine use

20/05/2008 LimitState:GEO launch & technology briefing - ICE London

Where does LimitState:GEO fit in? Hand calculations / simple programs Limit Equilibrium Geotechnical Category 2 Numerical limit analysis Geotechnical Category 2+ Non-linear finite elements Complex material models Geotechnical Category 3 more complex more input parameters more expertise required [potentially] more accurate LimitState:GEO

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Example application: slope stability Traditional methods still dominate: –over 40 commercial slope stability programs listed at

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Typical LimitState:GEO solution: i.e. more complex failure mechanisms may be critical! Example application: slope stability

20/05/2008 LimitState:GEO launch & technology briefing - ICE London geo1.0 Example applications: footings & tunnels

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Example applications: combined problems Combination problem with weak underlying layer Combination slope stability / gravity wall / footing

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Any other geometry… LimitState:GEO can model any geometry and any set of boundary conditions. The above example shows a solution available in the literature compared with the solution derived using LimitState:GEO. LimitState:GEO solution Gunns (1980) 3-variable block mechanism Anchor in cohesive soil

20/05/2008 LimitState:GEO launch & technology briefing - ICE London 04/06/2014 geo1.0 LimitState:GEO: how it works…

20/05/2008 LimitState:GEO launch & technology briefing - ICE London How does it work? At collapse a soil mass will break up into a series of individual blocks of soil LimitState:GEO uses novel numerical limit analysis technique Discontinuity Layout Optimization (DLO) to find the optimal arrangement of sliding blocks Outcome of University of Sheffield / EPSRC funded research: –Layout optimization research since 2000 –Discontinuity layout optimization research since 2005 –DLO paper published Proc. Royal Society A in 2007

20/05/2008 LimitState:GEO launch & technology briefing - ICE London How does it actually work? The problem is initially formulated not in terms of soil blocks (or elements) but in terms of the lines of discontinuity between them The critical layout of these lines is determined using rigorous optimization techniques discontinuity layout optimization The steps in the process will now be outlined

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Step 1: discretize using nodes

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Step 2: connect nodes to form a set of potential discontinuities

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Step 3: setup optimization problem Upper bound (mechanism) formulation: –Find minimum multiplier on specified loads (margin of safety, or adequacy factor) Subject to nodal compatibility constraints:

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Step 4: solve & display! Problem is a simple linear optimization problem (easy to solve) After solving can identify and then deform solid blocks to help interpretation:

20/05/2008 LimitState:GEO launch & technology briefing - ICE London Key points: 1.Central to DLO method is that discontinuities can crossover Therefore get many more elements for our money 2.More nodes gives more accurate solution 3.Frictional materials & self weight present no special difficulties

20/05/2008 LimitState:GEO launch & technology briefing - ICE London More advanced usage Can also treat many other types of problem, e.g containing: –Rotational failure mechanisms –Pre-existing slips –Structural elements –Etc etc.

20/05/2008 LimitState:GEO launch & technology briefing - ICE London 04/06/2014 geo1.0 Questions?