The latest project involving FEM simulations in COMSOL Multiphysics attempted to evaluate possible fracture refraction across layers of contrasting lithologies. Two types of layered models were chosen viz., M1: sandstone layers only and M2: sandstone layers separated by a layer of micaceous schist. The notches (see figures above) represent impurities and were used in 5 different combinations (see figures above) to trigger the formation of high strain zones (see figures above). For both the models, the magnitudes of the applied normal and shear stresses were increased over an interval of 2 sec. We showed that closely spaced impurities may curve the possible fracture domains across the layer boundaries producing a ‘false’ impression of refraction. Please check Bose et al. (2020) for more. 

As a part of my doctoral research, I developed a simple, time-dependent 2D-finite element model using triangular meshing in COMSOL Multiphysics. It aimed to examine the effect of two-stage deformations (see the figures above) on the rotation senses of elliptical clasts within a homogeneous matrix. It was noticed that although the clasts rotate with opposite senses during pure shear, the final products do NOT reveal the same i.e., the long axis of all the ellipses are tilted in the same direction (+X) with nearly the same tilt amount. This further shows how trickier establishing the sequence and evolution of shearing could be for multiply deformed terranes. Please check Dutta & Mukherjee (2019) for more. 

This work was a part of the doctoral thesis of one of my senior colleagues and my first attempt at FEM simulations using COMSOL Multiphysics. Herein, modelling was employed to evaluate the influence of sizes and distributions of grains/porphyroclasts on the brittle failure of the host rock. Three different types of models were developed. In model 1, all the circular porphyroclasts were of the same size and in contact with one another. However, in model 2 they were not in contact. Model 3 had two different sizes of porphyroclasts none of which was in contact with its neighbors. The results showed that coarser grains restrict the generation and growth of brittle P-planes - in agreement with our field observations. We further noticed that the chances of P-plane generation are much lower if the applied normal stress is higher than the shear stress. Please check Bose et al. (2018) for more.