You are reading the online version of the LimitState:GEO manual, which is also available as a pdf.

Introduction

General Description

LimitState:GEO is a general purpose software program which is designed to rapidly analyse the ultimate limit state (or ‘collapse state’) for a wide variety of geotechnical problems.

The software can be used to model 2D problems of any geometry specified by the user (including slopes, retaining walls, foundations, pipelines, tunnels, anchors etc. and any combination of these).

It directly determines the ultimate limit state (ULS) using the Discontinuity Layout Optimization (DLO) procedure (see DLO), and is designed to work with modern design codes such as Eurocode 7 by providing full support for partial factors and the ability to solve multiple scenarios.

Program Features

LimitState:GEO is designed to be general, fast and easy to use. The main features of LimitState:GEO are summarized below:

• LimitState:GEO utilizes Discontinuity Layout Optimization (DLO) to directly identify the critical collapse mechanism. The DLO procedure effectively relies on the familiar ‘mechanism’ method of analysis originally pioneered several centuries ago by workers such as Coulomb (1776), but posed in a modified form to allow modern-day computational power to be applied to the problem of finding the critical solution from billions of possibilities.
• The solution is presented as an ‘adequacy factor’ (applied to one or more loads in the problem) and also displayed visually as a failure mechanism involving a number of blocks which will slide and/or rotate relative to one another. To facilitate rapid interpretation of the mode of response the failure mechanism can be animated. The distribution of stresses around the edges of any constituent block can also be displayed.
• Many types of problems can be solved, including those involving slopes, foundations, gravity walls, and any combination of these. The problem geometry can be specified using Wizards for common problems or alternatively by:
  • drawing the geometry on-screen using the mouse,
  • importing from an AUTOCAD DXF file.

  The geometry can subsequently be edited using the mouse or by editing coordinates.

• The following Materials are available:
  • Mohr-Coulomb (strength defined in terms of cohesion intercept and angle of shearing resistance). A linear variation of with depth may also be specified.
  • Rigid (i.e. no yield conditions are applied).
  • Cutoff (allows modelling of a tension and/or compression cutoff).
  • Engineered element (e.g. for modelling a soil nail or sheet pile wall).
• A wide range of Wizards are provided to permit rapid modelling of common geotechnical problems, including slope stability, gravity wall, and foundation problems.
• The user may switch between long term and short term (drained and undrained) analysis modes by changing a single setting.
• The ground water conditions may be defined using:
  • a water level (phreatic surface) with hydrostatic pore pressures,
  • an overall value of the pore pressure coefficient .
• Soil reinforcement/Engineered elements and pre-existing slip surfaces may be modelled at any location within the geometry.
• Seismic loadings may be modelled using the pseudo static method by specifying Horizontal and Vertical accelerations.
• Choice of Translational or Translational and Rotational analysis modes.
• LimitState:GEO provides extensive support to users wishing to use Partial Factors:
  • user specified partial factor sets can be defined,
  • commonly used partial factor sets are built-in (e.g. Eurocode 7 Design Approach 1 partial factor sets),
  • different partial factors can be defined for permanent, variable, accidental and favourable / unfavourable loads (see here for further information),
  • automatic post-analysis checks are performed to verify that Favourable/Unfavourable load specifications are in fact correct.
• LimitState:GEO provides a comprehensive and easy to use GUI interface with fully selectable geometry objects, a Property Editor, Materials Explorer and drag and drop facilities. It also provides users with full Undo/Redo facilities and ability to recover lost work via an auto-saved recovery file.
• A comprehensive Report can be generated, with user control over what is included, and the unique ability to output free body diagrams for all blocks of material identified in the critical failure mechanism, with equilibrium equations to permit easy hand validation (see here for further information).
• Comprehensive guidance within the program in the form of messages, warnings and text descriptions. Where appropriate these are hyperlinked direct to relevant sections within the online help file.
• Choice of working in Metric or Imperial units.

LimitState:GEO Terminology

LimitState:GEO is designed to rapidly identify the critical failure mechanism in any geotechnical stability analysis problem. The following annotated image highlights the most important objects the user will encounter when using LimitState:GEO:

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About LimitState

LimitState Ltd was spun out from the University of Sheffield in 2006 to develop and market cutting edge ultimate analysis and design software for engineering professionals. LimitState:GEO follows on from LimitState:RING 2.0 as the second of several planned products, with applications in the structural, geotechnical and mechanical engineering sectors. Our aim is to be a world leading supplier of computational limit analysis and design software. LimitState maintains close links with the University of Sheffield, enabling it to draw on and rapidly implement the latest innovations in numerical and theoretical limit state analysis.

Using Help

Pressing F1 at any time gives users access to the online help facility, providing users with a convenient means of accessing material contained within the manual whilst using the software. The software also includes hyperlinks which link directly to relevant parts of the online help material (e.g. from within messages, dialogs and text descriptions), to provide users with rapid access to relevant explanatory material.

System Requirements

LimitState:GEO runs on the Windows 2000, XP, Vista and Windows 7 operating systems (support for Mac OSX and Linux operating systems is available on request, subject to demand). Recommended minimum system specifications are as follows (ideal values are given in parenthesis):

• 500MHz (1.5+ GHz) Intel (or compatible) processor
• 50Mb (200+ Mb) free hard disk space
• 512Mb (1+ Gb) RAM

Program Limits

The program uses a ‘Single Document Interface’ which means that one project file can be open in LimitState:GEO at any given time. However, several instances of LimitState:GEO can be opened simultaneously if required and each of these may contain a separate project file.

When using LimitState:GEO with a ‘full’ license, problem size is limited only by available computer power.

Contact Details

Sales

To request information on pricing, a formal quotation, or to purchase the software please contact Limitstate Ltd, at sales@limitstate.com.

Software Support

Software support for LimitState:GEO is available to all users with a valid support and maintenance contract. Additionally we are happy to help users with time-limited ‘trial’ or ‘evaluation’ licenses. All queries should be directed to support@limitstate.com.

Website

For the most up-to-date news about LimitState:GEO, please visit the LimitState:GEO website: www.limitstate.com/geo.