Prof. Ronaldo I. Borja, Stanford University -

Time: Tuesday, June 7, 2022 at 10-11 am

Place: Guttenberghaus, Feistmantelstrasse 4, 1180 Vienna, seminarroom 01 (SR-01)

Various modes and geometric styles of failure have been observed in different rocks. On the one hand, transversely isotropic rocks exhibit strength that varies with the orientation of bedding planes relative to the load. On the other hand, failure in high-porosity rocks commonly manifests itself in the form of compaction band that is generally aligned in the direction perpendicular to the maximum compressive stress. But so-called shear-enhanced compaction bands oriented obliquely with respect to the maximum compressive stress have also been observed in the field, while others such as wiggly and chevron compaction bands exhibit more intriguing geometric styles. In this talk, I will present continuum-based mechanical models that capture many of the aforementioned strength and geometric styles of failure observed in rocks. The tools that I will use include anisotropic elasticity, anisotropic plasticity, breakage mechanics, and phase-field modeling. My talk will cover both the prediction of strength and the formation and propagation of the localized failure zone. I will use anisotropic elasticity and plasticity to predict the strength variation as a function of bedding orientation in transversely isotropic rocks. Further, I will combine breakage mechanics and plasticity with phase-field modeling to initiate and propagate both pure and shear-enhanced compaction bands.

Ronaldo Borja works in theoretical and computational geomechanics, geotechnical engineering, and geosciences. His research includes the development of mathematical and computational frameworks for multiscale and multi-physical processes in geomechanics and related fields. He is the author of a textbook entitled Plasticity Modeling and Computation published by Springer and serves as executive editor of two journals: the International Journal for Numerical and Analytical Methods in Geomechanics and Acta Geotechnica. Ronaldo Borja is the recipient of the 2016 ASCE Maurice A. Biot Medal for his work in computational poromechanics.