Civil and Structural engineering

Software Tour

Geotechnical / Soil-structure modelling

Unlike some structural analysis software selected LUSAS Civil & Structural (and LUSAS Bridge) software products, when used with appropriate nonlinear, dynamic and thermal/field software options, provide a range of soils-specific and general structural engineering analysis tools to enable finite element modelling in 2D or 3D of both ground and structure in a single model. 

Multiple and branched analyses can be solved within each model, and state-of-the-art linear and quadratic element libraries; advanced material models; and linear and nonlinear joint models allow a range of soil-structure engineering problems to be solved.


Model building

LUSAS models are created using feature-based geometry methods (points, lines, surfaces and volumes) and built-in associativity - a key feature of the LUSAS Modeller - ensures that if the model geometry is amended, all assigned loadings, supports, mesh and other attributes are automatically updated to suit. 

  • CAD import / export facilities permit importing of point and line data from DXF files; points, lines, surfaces and volumes via IGES/STEP interfaces; and triangulated surface data through STL. CAD-style drawing tools provide an array of modelling utilities such as copy, rotate, scale, transform, extrude etc.
  • For 2D modelling, splines can be created from terrain points data and swept to create strata. Surfaces can be defined from bounding points and lines, and swept to define a soil mass. Structural and soil components can be grouped for modelling purposes. For 3D modelling, planar or curved surfaces can be swept for multiple volume creation, and intersection and subtraction commands provide the means to slice volumes or create voids.
  • Automatic 2D meshing (using quadrilateral/triangular elements) and 3D meshing (using tetrahedral/pentahedral/hexahedral elements) speeds up the modelling process. Various mesh refinement methods are provided.


  • Constitutive soils models include Tresca, Von Mises, Drucker Prager, Duncan-Chang, Hoek-Brown, Mohr Coulomb, and Modified Cam Clay. Add two-phase material properties to selected materials to permit modelling the deformation of undrained/fully saturated and fully-drained/unsaturated porous media, and slow consolidation process. Specify draining and filling curves for partially drained materials.
  • Residual soil stress varying with depth can be accommodated providing useful facilities for soil-structure interaction for integral bridges and culverts. Rock joints, pore water pressure dissipation, consolidation modelling, geotechnical problems involving long term excavation, construction in clays, and temporary works can all be solved.
  • Calculate initial stress states providing K0 data and apply to any ground profile.
  • Model the variation of soil properties with depth by defining soil profile variations, with LUSAS interpolating between defined locations.
  • Use nonlinear springs to model active/passive soil joints. Interface meshes permit joining of the soil / structure. Gain / loss of contact, and skin friction can be considered. 
  • Specify a matrix of properties to represent a pilecap sitting on a group of piles in a 3D model.
  • Use branched analyses to carry out Phi-c reduction stability checks at any stage of construction for soil represented by Mohr-Coulomb or Hoek-Brown material models.

  • Use the tri-linear (active/passive) earth pressure joint material wizard to simplify the modelling of a variety of soil-structure interaction problems, creating a piecewise linear joint material attribute with properties that vary with depth. Define multiple attributes to represent layers of soil or changes in properties due to the presence of water.

General geotechnical and soil-structure interaction capabilities include:

  • Construction sequence modelling - involving excavation / construction with insertion and removal of temporary members used for propping and jacking etc. 

  • Embankment /slope stability assessments and stability checks on adjacent structures due to temporary excavation. 

  • Backfilling of excavations and cut and cover tunnel structures. 

  • Settlement and consolidation including pore water pressure modelling. 

  • Dewatering and seepage modelling of partially saturated fluid flow through porous media, such as seepage of water through an earth dam, where the position of the phreatic surface is of interest. 

  • Modal and time history dynamics involving material damping, nonlinear behaviour, soil plasticity, boundary behaviour and springs/dampers. 

  • Soil-structure interaction analysis including vibration analysis from pile driving impact assessments on nearby buildings and response of buildings to emitted vibrations from rail tunnels. 

  • Lateral displacement analysis of piles and pile groups 

  • Integral bridges

Application areas

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LUSAS is a trademark and trading name of Finite Element Analysis Ltd. Copyright 1982 - 2022. Last modified: October 14, 2022 . Privacy policy. 
Any modelling, design and analysis capabilities described are dependent upon the LUSAS software product, version and option in use.