Growth of fluid-driven fractures in the viscous-dominated regime

We revisit the classical problem of a growing penny-shaped fracture formed upon injection of viscous fluid in a brittle solid. We report an experimental study on the injection of a viscous fluid at a constant flow rate. The fracture’s growth dynamics is controlled by the viscous dissipation in the fluid. Previous studies have shown discrepancies between theoretical predictions and experimental results. Our experiments show that the radius increases even after the injection is stopped, until it reaches an equilibrium value. We measure the fracture width and radius over time, for varying mechanical properties of the gel and injection parameters. The viscosity of the injected fluid, the injection flow rate and the total volume injected influence the fracture dynamics. Scaling arguments are provided to explain the experimental results and provide insights into the underlying physics.