  The width of fracture process zones in geomaterials is commonly assumed to
depend on the type of heterogeneity of the material. Still, very few techniques
exist, which link the type of heterogeneity to the width of the fracture
process zone. Here, fracture processes in geomaterials are numerically
investigated with structural network approaches, whereby the heterogeneity in
the form of large aggregates and low volume fibres is modelled geometrically as
poly-dispersed ellipsoids and mono-dispersed line segments, respectively. The
influence of aggregates, fibres and combinations of both on fracture processes
in direct tensile tests of periodic cells is investigated. For all studied
heterogeneities, the fracture process zone localises at the start of the
softening regime into a rough fracture. For aggregates, the width of the
fracture process zone is greater than for analyses without aggregates. Fibres
also increase the initial width of the fracture process zone and, in addition,
result in a widening of this zone due to fibre pull out.
