LimitState:GEO 3.0 was launched just over six months ago. This feature takes a look at some of the new functionality that was added to the software and how it helps make your life easier.
1. Analysis by factoring material strength
Many different definitions of factors of safety (FoS) are used in geotechnical engineering. Three in common usage are:
- Factor on load.
- Factor on material strength.
- Factor as ratio of resisting forces (or moments) to disturbing forces (or moments).
In previous versions of LimitState:GEO, failure was driven by factoring loads, whether they be externally applied or a material self-weight. Factoring material strength was possible, but by following a process of setting up a series of partial factors in different scenarios.
LimitState:GEO 3.0 now allows the user to switch to an analysis mode that adjusts the strength of the Mohr-Coulomb materials present in the problem until failure occurs, allowing quick determination of whether a construction is under / overdesigned for the chosen set of partial factors. This is particularly useful for problems of slope stability, where factoring loads is not the most natural method of analysis. Alternatively, when the material factoring mode is used and partial factors are set to unity, a global factor of safety on strength can be obtained, facilitating direct comparison with traditional methods.
An example outlining the use of the "Factor Strength(s)" analysis mode is given in Application Note LSG-AN8, which is available to download below, or from the Application Notes page.
2. Improved water modelling capability
In LimitState:GEO 3.0 a more versatile approach to modelling water pressures has been introduced - Water Regimes. These are defined and applied to zones in the same way as materials, allowing users to model not just a global water table, but also different water pressure distributions within each soil layer. Types of reigime available for use include:
- Constant potential - allows areas of positive or negative pressure (e.g. capillary rise).
- Uniform pressure - allows e.g. areas of zero pressure or constant suction.
- User-defined grid - allows spatially varying water pressures.
With these new representations, users are able to model features such as perched water tables, aquicludes and aquifers with ease.
Section 6.2 of the LimitState:GEO User Manual explains the different regime types in more detail.
3. Enhanced soil reinforcement & soil-structure modelling
The engineered element material has been updated to allow tensile, compressive and bending failures to be modelled. This allows enhanced modelling of commonly used elements such as geotextiles and soil nails within the software.
Furthermore, different interface materials can now be added to each side of an Engineered Element.
Post analysis tensile force and bending moment diagrams can be displayed for engineered elements and used to determine details such as:
- Tensile stress distribution in soil reinforcement
- Bending moment distributions in sheet pile walls