itech

Soil-structure interaction

For the design of retaining walls, tunnel lining, anchors, bolts and geogrids, CESAR-LCPC allows realistic modeling of the soil-structure interaction thanks to the availability of a wide range of dedicated elements such as contacts, trusses, beams, plates, shells, springs and linear relations.

Bond-slip and friction behaviour at the soil-structure interface is modelled in CESAR-LCPC using a robust and elaborate contact algorithm.

Three criteria are available:

no interpenetration,
Coulomb's friction,
tensile limit.

Pile group subjected to horizontal load

Soil-structure interaction: reinforcement

Proper modelling of soil reinforcement is essential to achieve an accurate description of the analysed mechanisms.

Reinforcement systems such as bolts, nails, anchors, micropiles or geotextiles can be modelled using structural elements such as trusses, beams or shells.

A second approach : the heterogeneous reinforced soil is replaced by an equivalent homogenous material. This approach is based on the theory of homogenisation of periodic media. This approach has the advantage of allowing the generation of meshes that are independ from the geometry of the inclusions. In CESAR-LCPC, the multi-phase model of Sudret and de Buhan (1999) is implemented.

Homogeneous

Radial

Cylindrical

Spherical

Modelling a pore pressure and groundwater flow

Groundwater can play a key role in geotechnical projects. With CESAR-LCPC, two approaches based on the Terzaghi assumption are available to model the effect of groundwater:

Hydrostatic equilibrium can be modelled using dry soil density above the water level and effective soil density below. A dedicated tool allows easy application of hydrostatic loading on the boundary of impermeable structural elements.
The effect of steady state or transient groundwater flow can be modelled by applying in the mechanical analysis the pore pressure forces obtained from a preliminary flow analysis.

CESAR-LCPC has advanced groundwater flow modules that can handle non-saturated transient flow. The pore pressure results of such an analysis can be used as loading in a mechanical analysis.

Consolidation analysis can also be carried out using the fully coupled poro-mechanical model available in a dedicated module of CESAR-LCPC.

Example of staggered flow-stress analysis in a dyke:
steady state groundwater flow analysis.

... followed by a mechanical analysis.

Bibliographical references

BOURGEOIS E., SEMBLAT J.-F., GARNIER D., SUDRET B.
Multiphase model for the 2D and 3D numerical analysis of pile foundations.
Tenth International Conference on computer methods and advances in geomechanics.
Tucson, Arizona (USA), 7-12 january 2001, p. 1435-1440.

MESTAT PH.
An overview on 25 years of numerical modeling of test embankments and tunnels.
Tenth International Conference on Computer methods and advances in geomechanics.
Tucson, Arizona (USA), 7-12 january 2001, p. 1521-1526.

MAGNAN J.-P., DRONIUC N.
Stability analyses in geotechnical engineering: recent developments.
Fourth International Geotechnical Engineering Conference.
Cairo University (Egypt), 24-27 janvier 2000, p. 57-90.

BAY-GRESS C., SIEFFERT J.G., LAUE J.
Behaviour of shallow foundations under complex loading.
International Conference on Soil-Structure Interaction in Urban Civil Engineering.
Darmstadt (Germany), 8-9 October 1999, p. 357-370.

GODART B.
Influence of foundation settlement on the behaviour of Strasbourg cathedral, France.
Structural Engineering International, volume 11, n° 4, p. 223-227.

RIOU Y., CHAMBON P.
An elastoplastic analysis of 3-D ground movements.
NUMGE 98 - Fourth European Conference on Numerical methods in Geotechnical Engineering.
Udine (Italy), 14-16 october 1998, p. 181-190.

ZENTAR R., MOULIN G., HICHER P.-Y.
Numerical analysis of pressuremeter test in soil.
NUMGE 98 - Fourth European Conference on Numerical methods in Geotechnical Engineering.
Udine (Italy), 14-16 october 1998, p. 593-600.

UNTERREINER P., BENHAMIDA B., SCHLOSSER F.
Finite element modelling of the construction of a full-scale experimental soil-nailed wall.
French National Research Project CLOUTERRE.
Ground Improvement 1, p. 1-8.

BENSLIMANE A., JURAN I., BRUCE D.A.
Group and network effect in micropile design pratice.
14e Congrès International de Mécanique des Sols et des Travaux de Fondations,
Hamburg (Germany), 6-12 September 1997, Proceedings Balkema, Vol. 2, p. 767-770.

ANTAO A., MAGNAN J-P., LECA E., MESTAT PH., HUMBERT P.
Finite element method and limit analysis for geotechnical design.
6th International Symposium on Numerical Models in Geomechanics - NUMOG VI,
Montreal, Quebec (Canada), 2-4 July 1997, Proceedings Balkema, p. 433-438.

QUIERTANT M., SHAO J.F., TRENTESAUX C.
Stress measurement in elastoplastic ductile geomaterials.
6th International Symposium on Numerical Models in Goemechanics. NUMOG VI.
Montreal, Quebec (Canada), 2-4 July 1997, Proceedings Balkema, p. 513-518.

BENHAMIDA B., UNTERREINER P., SCHLOSSER F.
Numerical analysis of a full-scale experimental soil-nailed wall.
3rd International Conference on Ground Improvement Geosystems,
London (United Kingdom), 3-5 June 1997, Proceedings Thomas Telford, p. 452-459.

JIANG G.L., MAGNAN J.P.
Stability analysis of embankments : comparison of limit analysis with methods of slices.
Géotechnique, Vol. 47, n° 4, 1997, p. 857-872.

NASRI V., MAGNAN J.-P.
Effect of soil consolidation on the space frame-raft-soil interaction.
ASCE, Journal of Structural Engineering, volume 123, n° 11, p. 1528-1534.

VENGEON J-M., HANTZ D., GIRAUD A., RACT D.
Numerical modelling of rock slope deformations.
EUROCK'96, ISRM International Symporium,
Turin (Italy), 2-5 September 1996, Proceedings Balkema, p. 659- 666.

BERNAT S., CAMBOU B., DUBOIS P.
Modelling of tunnel excavation in soft soil.
NUMOG V Numerical Models in Geomechanics,
Davos (Switzerland), 6-8 September 1995, p. 471-475.

BRIOIST J.J., HUMBERT P., MESTAT PH.
Some remarks on the validation of finite element codes in geotechnics.
NUMOG V Numerical Models in Geomechanics,
Davos (Switzerland), 6-8 September 1995, p. 681-686.

HUMBERT P., MESTAT PH.
Three-dimensional modelling of a foundation.
11th European Conference on Soil Mechanics and Foundation Engineering.
Copenhagen (Denmark), 28 May-1 June 1995, Vol. 6 Bulletin 11, p. 63-68.

MAGNAN J.-P., KATTAN A.
Additional analysis and comments on the performance of Mua Flats trial embankment to failure.
International Symposium on trial embankments on Malaysian marine clays.
Kuala Lumpur (Malaysia), 6-8 november 1989, p. 11.1-11.7.