Events

Speaker:  Dr. Andrew Bunger, Associate Professor of Civil and Environmental Engineering, University of Pittsburgh

Title of Seminar: “The Making of Hydraulic Fracture and Dyke Swarms”

Abstract: I will tell of a pursuit to identify the ingredients required for swarming behavior to occur in systems of fluid-driven cracks, namely, hydraulic fractures and magma-driven dykes. I will show that key missing elements have included: 1) a basic understanding of the attractive force in these systems, that is, why fluid-driven cracks would have any mechanical impetus to grow near one another in the first place, and 2) a model capable of predicting conditions in which subsequent fluid-driven cracks can initiate even when fluid pressure is limited by flow in previously-initiated fluid-driven cracks. A combination of theory, laboratory experiments, and numerical simulation show that the ability to initiate and sustain propagation of multiple fluid-driven cracks stems from the dependence of these key ingredients on geometry, the relative importance of viscous energy dissipation in the context of the energy balance of the system, and time-dependent failure of rocks rooted in subcritical crack growth. Finally, looking to the future, I will discuss how this research provides a story of both success and caution, emphasizing the need to hold reductionism and complexity in tension with one another as we seek models that are more representative of observed reality while pursuing this goal in systematic manner that allows us understand what is driving the behavior generated by the models we are developing.

Biography: Andrew Bunger is an Associate Professor in the University of Pittsburgh's Department of Civil and Environmental Engineering. He joined the University of Pittsburgh in 2013 after spending 10 years in Melbourne, Australia working in the Geomechanics Group within the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Prior to that, he received his PhD in Geological Engineering from the University of Minnesota. His research interests include the mechanics of hydraulic fractures, coupled fluid-shale interaction, and the emplacement dynamics of magma-driven dykes and sills.