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SUMMARY:Virtual MEchanics GAthering -MEGA- Seminar: Propagation of a plane
 -strain hydraulic fracture accounting for a rough cohesive zone
DTSTART:20201203T161500
DTEND:20201203T173000
DTSTAMP:20260509T215454Z
UID:864fb1bc395aa5f3d49857766e810f66eb89b92813f7e7dc844ba7ae
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dong Liu (GEL\, EPFL)\nAbstract: The quasi-brittle nature of 
 rocks challenges the basic assumptions of linear hydraulic fracture mechan
 ics (LHFM): namely\, linear elastic fracture mechanics and smooth parallel
  plates lubrication fluid flow inside the propagating fracture. We relax t
 hese hypotheses and investigate in details the growth of a plane-strain hy
 draulic fracture in an impermeable medium accounting for a rough cohesive 
 zone and a fluid lag. In addition to a dimensionless toughness  and the 
 time-scale of coalescence of the fluid and fracture fronts governing the f
 racture evolution in the LHFM case\, the solution now also depends on the 
 ratio between the in-situ and material peak cohesive stress and the intens
 ity of the flow deviation induced by aperture roughness (captured by a dim
 ensionless power exponent). We show that the fracture growth is characteri
 zed with three distinct stages: a nucleation phase for the cohesive zone\,
  an intermediate stage\, and late time stage where convergence toward LHFM
  predictions finally occurs. A highly non-linear hydro-mechanical coupling
   takes place as the fluid front enters the rough cohesive zone which it
 self evolves during the nucleation and intermediate stages of growth. This
  coupling leads to significant additional viscous flow dissipation. As a r
 esult\, the fracture evolution deviates from LHFM predictions with shorter
  fracture lengths\, larger widths and net pressures. These deviations from
  LHFM ultimately decrease at late times as the ratios of the lag and cohes
 ive zone sizes with the fracture length both become smaller. The deviation
 s increase with larger dimensionless toughness and larger in-situ-to-cohes
 ive stress ratio\, as both have the effect of further localizing viscous d
 issipation near the fluid front located in the small rough cohesive zone. 
 The impact of a rough cohesive zone appears to be prominent for laboratory
  experiments and  short in-situ injections in quasi-brittle rocks with u
 ltimately a larger energy demand compared to LHFM predictions.\n \n\nBio:
  Dong Liu got his master’s degree in civil engineering and material sci
 ence for sustainable construction in Ecoles des Ponts in France and Tongj
 i University in China in 2016. He then joined the Geo-energy laboratory (
 GEL) at EPFL as a Ph.D. candidate. His research interests include hydrauli
 c fracturing\, emplacement of magmatic dikes\, and geophysics. 
LOCATION:Zoom: epfl.zoom.us/s/98393329833 Room Passcode: 349948 http://epf
 l.zoom.us/s/98393329833
STATUS:CONFIRMED
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