ORALS

The present work models problems in which the initiation and propagation of cracks in porous materials represents a key issue and is strongly influenced by the interaction between the solid matrix and the fluid in pores. The methodology is based on a work by the authors already published [1]. In this case, discontinuities are modelled by means of quasi-zero-thickness interface elements using an FEM-based approach. These special elements, which can be used to define either pre-existing or propagating cracks, act as joints that allow representation of the jump in the displacement field and the directional preferences in the fluid flow. To ensure that the direction of the crack growth is not heavily influenced by the mesh, a non-local damage model is used to predict the degradation pattern of the domain and the interface elements are then inserted, followed by a remeshing. FIC-stabilized elements of equal order interpolation in the displacement and the pore pressure have been successfully used under complex conditions near the undrained-incompressible limit [2]. A bilinear cohesive fracture model describes the mechanical behaviour of the joints. A formulation derived from the cubic law models the fluid flow through the crack. Examples in 2-D and 3-D, using 3-noded triangles and 4-noded tetrahedra respectively, are presented to illustrate the features of the proposed methodology in hydraulic fracture processes. Other examples solved by the authors using joint elements in dam engineering [3] will be shown to introduce some of their alternative applications.

References:
[1] De-Pouplana, I. and Oñate, E., Finite element modelling of fracture propagation in saturated media using quasi-zero-thickness interface elements, Computers and Geotechnics (2017), http://dx.doi.org/10.1016/j.compgeo.2017.10.016 .
[2] I. de Pouplana and E. Oñate. A FIC-based stabilized finite element method with equal order interpolation for solid-pore fluid interaction problems. International Journal for Numerical and Analytical Methods in Geomechanics, vol. 41, pp. 110-134, 2016. DOI: 10.1002/nag.2550
[3] I. de Pouplana, L. Gracia, F. Salazar and E. Oñate. Cracking of a concrete arch dam due to seasonal temperature variations. Proceedings of the 14th International Benchmark Workshop on Numerical Analysis of Dams, pp. 147-156, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-223593