Finite elements and constitutive laws for the non-linear modeling of dams

26 January 2014

by E. Robbe, EDF / CIH and K. Kazymyrenko, J. Laverne, V. Guyonvarh, EDF R&D / AMA

By design, concrete dams feature discontinuities which may be solicited during the operating lifespan of the structure :

  • contact between the dam and its foundation,
  • vertical joint pads destined to minimize cracking during the shrinkage of the concrete,
  • horizontal joints following the resumption of casting concrete in the construction process.

The response of the structure to water pressure, temperature variations or even earthquake may be altered by the non-linear behavior at these interfaces.

Figure 1: Arch dam construction with joint pads

For several years, Code_Aster has been equipped with finite elements for joint modeling ( 3D_JOINT for mechanics only, 3D_JOINT_HYME for hydro-mechanical coupling) which have been improved regularly. In association with constitutive laws (JOINT_MECA_RUPT for unilateral behavior in tension and compression, JOINT_MECA_FROT for Mohr-Coulomb behavior), they enable proper modeling of the interfaces with short time to solution.

Figure 2: Numerical model of a dam (foundation, pads, right bank abutment)

Particular attention was paid to the development of specific modules for the mechanical analysis of dams. These include :

  • The account for the uplift under the dam with a coupled hydro-mechanical calculation: the opening of the joint is accentuated by the water pressure propagating in the crack ;
  • The ability to simulate the keying operation of the whole structure (step of injecting cement grout into the vertical joint pads to confer the dam its monolithic nature) ;
  • And lastly the ability to model sawing: such repairs may be considered to reduce stresses in dams affected by concrete swelling.
Figure 3: Joints opening and pressure in joints under hydrostatic loading