  Understanding and controlling fracture propagation is one of the most
challenging engineering problems, especially in the oil and gas sector,
groundwater hydrology and geothermal energy applications. Predicting the
fracture orientation while also possessing a non-linear material response
becomes more complex when the medium is non-homogeneous and anisotropic.
Fracturing behaviour in geological porous media that exhibit high leak-off
potential is not clearly understood. In this context, a novel testing technique
is used to simulate the ground conditions in the laboratory and study the
instability characteristics of such geo-materials. The bespoke apparatus
designed and developed in this research programme is capable of applying true
anisotropic boundary stresses, injecting fluid at a predefined flow rate and
viscosity while also imaging the instability/ fracture propagation in a porous
medium such as sand and weak rock. Pressure profiles and the progression of
fracture are recorded simultaneously during the fluid injection process into
specimens subjected to different boundary stresses. The fracture propagation
data are analysed, which provides information on the evolution of fracture
morphology and expansion velocity during the injection event.
