Quantifying the effect of pressure drop and fluid expansion on dynamic rock fracturing through synchrotron high-resolution microtomography

Rock failure by dynamic unloading is a common mechanical process in the Earth’s crust (earthquakes, underground rock mass excavation) but has been little studied experimentally due to technical challenges. We conceived new experiments deforming water-saturated rocks under virtually instantaneous decompression after being loaded at high pressures and temperatures. Preliminary lab-based X-ray CT suggest that the induced dynamic fracturing is positively correlated with the pressure drops but it is dramatically enhanced when the pore water vaporises/degasses during decompression. Such phase transitions might play a big, so far neglected, role in sustaining the initial stages of dynamic fracturing in the crust. To assess the magnitude of these processes, it is vital to fully quantify the 3D fracture network of the experimental samples to submicrometric resolution through synchrotron-light X-ray microtomography. These unique data can help to close a current knowledge gap in rock mechanics.