Nanomechanics of Gas Shale

Gas shale is relevant in many energy-related applications such as hydraulic fracturing in unconventional reservoirs, nuclear waste storage, or carbon dioxide geological capture and sequestration. The challenge consists in relating the mechanical performance of organic-rich shale to the structure and composition at different length-scales.  A hierarchical material, gas shale is extremely heterogeneous and strong controls are needed to offset the influence of extrinsic parameters on the resulting behavior.  Our approach is focused on depth-sensing methods, advanced multi-scale modelling and advanced imaging.


Pooyan Kabir, Franz-Josef Ulm, Ange-Therese Akono, Rate-Independent Fracture Toughness of Grey and Black Kerogen-Rich Shales, Acta Geotecnica, doi:10.1007/s11440-017-0562-0, (2017).

Ange-Therese Akono, Franz-Josef Ulm, Microscopic Toughness of Viscous Solids via Scratching: From Amorphous Polymers to Gas Shale,  Journal of Nanomechanics and Micromechanics, Vol. 7, (2017).

Ange-Therese Akono, Pooyan Kabir, Nano-scale characterization of organic-rich shale via indentation methodsNew Frontiers in Oil and Gas Exploration, pp. 209-233, (2016)

Ange-Therese Akono, Pooyan Kabir, Microscopic Characterization of Gas Shale via Scratch Testing, Mechanics Research Communications, Vol. 78, Part B, pp. 86-92, (2016)

Ductile-to-Brittle Transition In Scratch Testing

Scratch testing is a standard rock mechanics testing method with relevance in rock excavation, oilwell drilling, and unconventional resources extraction applications. By application of Bazant’s size effect law, we show that the ductile-to-brittle transition is governed by the depth at the microscopic scale and by the blade with and width-to-depth ratio at the macroscopic scale.


Ange-Therese Akono, Letter to the Editor Reply to “Discussion on the Fracture mechanics interpretation of the scratch test by Akono et al.Engineering Fracture Mechanics, Vol. 178, pp. 14-21, (2017).

Ange-Therese Akono, Energetic Size Effect Law at the Microscopic Scale: Application to Progressive-load Scratch TestingASCE’s Journal of Nanomechanics and Micromechanics, Vol. 6, (2016).

Ange-Therese Akono, Gregory A. Bouche, Rebuttal: shallow and deep scratch tests as powerful alternatives to asses the fracture properties of quasi-brittle materials, Engineering Fracture Mechanics, Vol. 158, pp. 23-38, (2016).

A.-T. Akono, F.-J. Ulm, Z. P. Bazant, Discussion: Strength-to-fracture scaling in scratchingEngineering Fracture Mechanics, Vol. 119, pp. 21 (2014).