Design of sand-based, 3D-printed analogue faults with controlled
frictional properties
Abstract
Laboratory experiments with surrogate materials play an important role
in fault mechanics. They allow improving the current state of knowledge
by testing various scientific hypotheses in a repeatable and controlled
way. Central in these experiments is the selection of appropriate
analogue, rock-like materials. Here we investigated the frictional
properties of sand-based, 3D-printed materials. Pursuing further recent
experimental works, we performed detailed uniaxial compression tests,
direct shear and inclined plane tests in order to determine a) the main
bulk mechanical parameters of this new analogue material, b) its viscous
behavior, c) its frictional properties and d) the influence of some
printing parameters. Complete stress-strain / apparent
friction-displacement curves were presented including the post-peak,
softening behavior, which is a key factor in earthquake instability.
Going a step further, we printed rock-like interfaces of custom
frictional properties. Based on a simple analytical model, we designed
the a) maximum, minimum and residual apparent frictional properties, b)
characteristic slip distance (d_c), c) evolution of the friction
coefficient with slip and d) dilatancy of the printed interfaces. This
model was experimentally validated using interfaces following a
sinusoidal pattern, which led to an oscillating evolution of the
apparent friction coefficient with slip. This could be used for
simulating the periodical rupture and healing of fault sections.
Additionally, our tests showed the creation of a gouge-like layer due to
granular debonding during sliding, whose properties were quantified. The
experimental results and the methodology presented make it possible to
design new surrogate laboratory experiments for fault mechanics and
geomechanics.