  The mechanics of cohesive or cemented granular materials is complex,
combining the heterogeneous responses of granular media, like force chains,
with clearly defined material properties. Here, we use a discrete element model
(DEM) simulation, consisting of an assemblage of elastic particles connected by
softer but breakable elastic bonds, to explore how this class of material
deforms and fails under uniaxial compression. We are particularly interested in
the connection between the microscopic interactions among the grains or
particles and the macroscopic material response. To this end, the properties of
the particles and the stiffness of the bonds are matched to experimental
measurements of a cohesive granular media with tunable elasticity. The
criterion for breaking a bond is also based on an explicit Griffith energy
balance, with realistic surface energies. By varying the initial volume
fraction of the particle assembles we show that this simple model reproduces a
wide range of experimental behaviors, both in the elastic limit and beyond it.
These include quantitative details of the distinct failure modes of
shear-banding, ductile failure and compaction banding or anti-cracks, as well
as the transitions between these modes. The present work, therefore, provides a
unified framework for understanding the failure of porous materials such as
sandstone, marble, powder aggregates, snow and foam.
