• The buildings of the IfG Leipzig - Südwerkbunker (left) and the Kauengebäude (right)

    The buildings of the IfG Leipzig - Südwerkbunker (left) and the Kauengebäude (right)

  • The rock mechanical laboratory of the IfG Leipzig

    The rock mechanical laboratory of the IfG Leipzig

  • Drilling cores of the Leine rock salt (Na3)

    Drilling cores of the Leine rock salt (Na3)

  • Dimensioning

    Dimensioning

  • Large-diameter borehole experiment in Springen

    Large-diameter borehole experiment in Springen

  • Modelling of a cavern

    Modelling of a cavern

  • Subsidence over a	cavitary field (modelling)

    Subsidence over a cavitary field (modelling)

Geomechanical modeling

For the geomechanical modelling and computer simulation of rock behaviour, modern personal computers and parallel computers are available. A series of program systems with respect to continuum and discontinuum mechanics is used, which allow the evaluation of planar and three-dimensional problems under statical and dynamical loading conditions:

 

  • The IfG developed and improved permanent material models as well as procedure for calculation and defines the state of science in the salt mechanics. The material models are validate by laboratory datas and in-situ measurement and find application in mining, storage and disposal. FLAC, FLAC3D, UDEC, 3DEC, PFC2D und PFC3D of ITASCA, with constitutive equations which were developed by IfG for special geomechanical problems and implemented in the source code of the programs:

    • Material law after Minkley

      Visco-elastoplastic material model with softening, dilatancy and (primary, secondary and tertiary) creep to describe the time-dependent softening behavior of salt rocks preceding creep fracture in combination with a shear model describing interface properties:

      Minkley, W., Mühlbauer, J. (2007): Constitutive models to describe the mechanical behavior of salt rocks and the imbedded weakness planes. In K.-H. Lux, W. Minkley, M. Wallner, & H.R. Hardy, Jr. (eds.), Basic and Applied Salt Mechanics; Proc. of the Sixth Conf. on the Mech. Behavior of Salt. Hannover 2007. Lisse: Francis & Taylor (Balkema). S. 119-127.

      Minkley, W., M. Knauth and D. Brückner. 2013. Discontinuum-mechanical behaviour of salt rocks and the practical relevance for the integrity of salinar barriers. In Proceedings of the 47th US Rock Mechanics/Geomechanics Symposium 23-26 June 2013, San Francisco, California, USA, eds. L. J. Pyrak-Nolte, A. Chan, W. Dershowitz, J. Morris and J. Rostami.

    • Material law after Günther/Salzer

      A model for rock salt, describing transient, stationary, and accelerated creep and dilatancy.

      Günther, R.-M. & K. Salzer (2007): A model for rock salt, describing transient, sta-tionary, and accelerated creep and dilatancy. In K.-H. Lux, W. Minkley, M. Wallner, & H.R. Hardy, Jr. (eds.), Basic and Applied Salt Mechanics; Proc. of the Sixth Conf. on the Mech. Behavior of Salt. Hannover 2007. Lisse: Francis & Taylor (Balkema). S. 109 – 117.

      Günther, R.-M. and K. Salzer (2012): Advanced strain-hardening approach: A powerful creep model for rock salt with dilatancy, strength and healing. In Proceedings of the 7th Conference on Mechanical Behavior of Salt, Paris, 16–19 April 2012, eds. P. Bérest, M. Ghoreychi, F. Hadj-Hassen, and M. Tijani, 13–22. Leiden: CRC Press/Balkema.

    • Adhesive friction model after Minkley

      Specific bedding plane model for boundary layer in salt rock formations (includes not linear shear strength, adhesion and slide friction as well as shear softening).

      Minkley, W., Groß, U.: (1988): Zum Haftreibungsverhalten an Gesteinstrennflächen in Abhängigkeit von der Belastungsgeschichte. Felsbau 6 (1988) Nr. 4, 184-188.

      Minkley, W. (2004): Zum mechanischen Verhalten von Diskontinuitäten im Salzgebirge. BAF Freiberg - Institut für  Geotechnik, 33. Geomechanik Kolloquium, Nov. 2004, Veröffentlichung IFGT Freiberg, Heft 2004-4, 113-126.

    • Discontinuum mechanical modeling of salt rocks

      Modeling approach, which consider the polycrystalline structure of salt rocks. The mechanical behaviour of salt crystals is described with a visco-elastoplastic material model and the intercrystalline interaction on the grain boundaries with the adhesive friction model. Important processes like fracturing, fragmentation and pressure-driven percolation along grain boundaries can be physically explained under consideration of the microstructure of salt rocks:

      Minkley, W., Knauth, M., Wüste, U. (2012): Integrity of salinar Barriers under consideration of discontinuum-mechanical aspects. Mechanical Behavior of Salt VII. Taylor & Francis Group, 469 - 478.

      Minkley, W., Knauth, M., Brückner, D. (2013):Discontinuum-mechanical behaviour of salt rocks and the practical relevance for the integrity of salinar barriers. Proc. of the 47th US Rock Mechanics/Geomechanics Symposium 23-26 June 2013, San Francisco, California, USA.

      • MKEN, SENK as a special software development of the IfG for the calculation of timedepending stress-deformation-areas around unterground cavities and for the forecast of mining damage at the surface.

  • Application:
    • Recalculation of laboratory tests for model matching and validation, e.g. triaxial test or creep test
    • Mining dimension of the determination of the the pillar load capacity to the static and dynamic system stability of the mining claims
    • Salt cavern dimension for leaching recovery and determination of the allowable storage pressure and rates during the operation of gas storage caverns to the long term behaviour after encapsulation
    • Dynamic processes like pillar failure and rock bursts
    • Final disposal of toxic or radioactive waste, in consideraion of thermal effects
    • Integrity of geological barrier and hydraulical protection layer during potash and rock salt mining as well as final disposals