The effect of sample strength on fracturing

Compression experiments comparing fracture development using the initial strength of the sample material.The movies show the development of fractures with layering on the left-hand side to help with interpretation and the evolution of failure on the right (the intensity of colour indicating the number of bonds broken). The number on the file shows the breaking strain of the bonds between elements where 0.01 is the weakest and 0.09 the strongest. Once the separation between a pair of elements exceeds the breaking strain the bond between the element pair is broken and no tensional force is exerted. Later compressional contacts, however, exert a force on the elements to push them apart. The left- and right-hand boundary elements behave as a jacket to constrain the sample. Initial fractures are oriented at 60/30 degrees to the compressing plates, but the models are pushed beyond the development of the first through-going fracture resulting in the higher angle cross-cutting faults present at the end of the movies.Comparison between experiments from weakest to strongest sample material is presented in the '*_all.gif' files relative to both layers and bonds. This is complimented by movies in the following link which show an investigation of the influence of interbedded stronger material in a sample.