BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:DEM\, dams and dikes - Catherine O'Sullivan\, Imperial College
DTSTART:20200521T103000Z
DTEND:20200521T113000Z
UID:TALK140689@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Embankment dams and flood embankments are probably the largest
 \, man-made\, structures that comprise particulate materials (soil).  The 
 talk will focus on internal erosion\, a phenomenon where water seeping thr
 ough the embankment can erode some of the embankment materials and pose a 
 risk to embankment integrity.\nTwo key mechanisms will be considered: (1) 
 the performance of filters which layers of sand and gravel placed to preve
 nt erosion of low permeability\, fine-grained material and (2) seepage ind
 uced internal instability\, a mechanism which involves preferential erosio
 n of the finer grains in the embankment filter and transition materials or
  in the embankment foundation.\nConsidering firstly filter performance\, e
 ngineers have long recognized the importance of the size of the narrowest 
 points in the void space\, which are called constrictions or pore throats.
  Hitherto attempts to estimate constriction sizes have relied on a number 
 of unproven hypotheses. DEM enables a direct measurement of the sizes of t
 he constrictions in virtual filter samples.  Micro Computed Tomography dat
 a can be used to confirm the relevance of DEM-derived data.  Network analy
 sis can be used to understand the basic mechanisms involved in filter perf
 ormance.  \nIn a gap-graded material\, where there are a mixture of coarse
  and finer grains\, there can be significant inhomogeneity.  The amount of
  the overall stress transmitted by the finer grains can be very small\, pa
 rticularly when the proportion of finer grains in the material is small.  
 Consequently these materials can fail lower hydraulic gradients that are t
 ypically considered safe in engineering design.  DEM simulations have been
  used to examine in detail the relationship between this stress inhomogene
 ity and both the proportion of finer grains and the size of the coarse gra
 ins relative to the finer grains.   Coupled DEM-CFD simulations have then 
 confirmed that the proportion of stress in the finer grains influences the
  likelihood that these grains will be transported under the action of seep
 age flow.\n
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
END:VEVENT
END:VCALENDAR