Intrusion of yield-stress fluid beneath an elastic membrane

We investigate a yield-stress fluid intrusion beneath an elastic membrane by deploying experiments and in numerical simulations. Our results show that the dynamics of the intrusion is clearly influenced by the yield-stress property of the fluid, as both the time evolution of the height and radius of the rising fluid blister follow different power-laws in the elastic regime, as a function of the fluid's yield-stress threshold. A higher yield-stress leads to bumps with steeper shapes and slower radial expansion, consistent with conservation of mass. As expected, for smaller yield-stress the dynamics become closer to when the intruding liquid is Newtonian. In the elastic regime, the inner region of the blister takes the same quasi-static shape independent of the fluid's yield-stress threshold. Thus, we expect the changing power-laws to be controlled by local effects at the propagating front, steered by the non-Newtonian properties. The findings from studying the viscoplastic intrusion can provide valuable new insights in the geoscientifical context of magmatic intrusions into the earth's crust and land formation.