  In both nature and engineering, loosely packed granular materials are often
compacted inside confined geometries. Here, we explore such behaviour in a
quasi-two dimensional geometry, where parallel rigid walls provide the
confinement. We use the discrete element method to investigate the stress
distribution developed within the granular packing as a result of compaction
due to the displacement of a rigid piston. We observe that the stress within
the packing increases exponentially with the length of accumulated grains, and
show an extension to current analytic models which fits the measured stress.
The micromechanical behaviour is studied for a range of system parameters, and
the limitations of existing analytic models are described. In particular, we
show the smallest sized systems which can be treated using existing models.
Additionally, the effects of increasing piston rate, and variations of the
initial packing fraction, are described.
