Emergence of anomalous transport in stressed rough fractures

• Published in: Earth and planetary science letters 2016-11, Vol.454 (C), p.46-54
• Main Authors: Kang, Peter K., Brown, Stephen, Juanes, Ruben
• Format: Article
• Language: English
• Subjects: anomalous transport; Asymptotic properties; Channels; Contact stresses; Emergence; fracture; Fracture mechanics; groundwater flow; Markov models; roughness; spatial Markov model; Spreading; Transport
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2016.08.033

We report the emergence of anomalous (non-Fickian) transport through a rough-walled fracture as a result of increasing normal stress on the fracture. We show that the origin of this anomalous transport behavior can be traced to the emergence of a heterogeneous flow field dominated by preferential channels and stagnation zones, as a result of the larger number of contacts in a highly stressed fracture. We show that the velocity distribution determines the late-time scaling of particle spreading, and velocity correlation determines the magnitude of spreading and the transition time from the initial ballistic regime to the asymptotic anomalous behavior. We also propose a spatial Markov model that reproduces the transport behavior at the scale of the entire fracture with only three physical parameters. Our results point to a heretofore unrecognized link between geomechanics and particle transport in fractured media. •Transport on a rough fracture transitions from Fickian to non-Fickian as confining stress increases.•Confining stress induces self-organization of flow into preferential channels and stagnation regions.•We propose a parsimonious stochastic transport model that captures the transition to anomalous transport.