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SUMMARY:Large poromechanical deformation of a frictional material - Chris 
 MacMinn (Oxford)
DTSTART:20141117T130000Z
DTEND:20141117T140000Z
UID:TALK55101@talks.cam.ac.uk
CONTACT:Doris Allen
DESCRIPTION:Flow through a porous material will drive mechanical deformati
 on when the fluid pressure becomes comparable to the stiffness or strength
  of the solid skeleton. This has applications ranging from hydraulic fract
 ure for the recovery of shale gas\, where fluid is injected at high pressu
 re\, to the mechanics of biological cells and tissues\, where the solid sk
 eleton is very soft. Both biological materials and geological ones can acc
 ommodate large deformations\, but they do so very differently: Biological 
 materials typically have a fibrous microstructure that stretches elastical
 ly\, whereas geological materials often have a frictional\, granular micro
 structure that fails plastically. Here\, we consider some consequences of 
 this distinction in the context of large poromechanical deformation driven
  by fluid injection. We motivate the problem with an experiment: Fluid inj
 ection into a packing of soft particles. Using high-resolution imaging\, w
 e measure the full deformation field and we study the dynamic interplay be
 tween grain-scale rearrangements and the macroscopic response. We show tha
 t the deformation involves a complex combination of rearrangement\, shear 
 failure\, and the quasi-reversible storage and release of elastic energy. 
 We then develop a mathematical model by posing this problem in a large-def
 ormation framework and incorporating frictional shear failure. We show tha
 t this model successfully captures certain macroscopic (continuum-scale) a
 spects of our experiments. We also compare the large-deformation model wit
 h the predictions of linear poroelasticity to highlight the importance of 
 volume conservation.
LOCATION:MR5\, Centre for Mathematical Sciences
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