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SUMMARY:On dangerous ground: understanding earthquake induced soil liquefa
 ction - Professor Gopal Madabhushi\, Geotechnical and Environmental Resear
 ch Group\,  Department of Engineering
DTSTART:20171023T170000Z
DTEND:20171023T180000Z
UID:TALK72361@talks.cam.ac.uk
CONTACT:Beverley Larner
DESCRIPTION:Earthquakes cause tremendous damage to man-made structures. So
 il liquefaction and the associated phenomena are the main cause for extens
 ive damage to infrastructure. Solid ground that normally offers good suppo
 rt to the structures can turn into a semi-liquid state temporarily under t
 he action of earthquake loading. This results in structures sinking into t
 he ground and/or rotating severely. Underground structures such as tunnels
  and pipelines can float towards ground surface.  \n\nIn this lecture exam
 ples of damage to structures from soil liquefaction observed in the recent
  earthquakes such as the New Zealand earthquakes of 2011\, Haiti earthquak
 e of 2010 and other such events will be presented. The basic mechanisms at
  play while the granular matter turns into a semi-liquid state will be dis
 cussed. Modelling of liquefaction problems is very interesting. Mathematic
 ally it involves solving of coupled differential equations if one follows 
 the finite element method. Physically\, liquefaction modelling requires th
 e use of a high gravity centrifuge in conjunction with powerful earthquake
  actuators that fly on the centrifuge. The development of earthquake actua
 tors at Cambridge from simple mechanical Stored Angular Momentum (SAM) act
 uator to the sophisticated Servo-hydraulic actuators will be highlighted. 
  Some example problems will be considered which were modelled using both m
 athematical and physical modelling tools. Some of the boundary value probl
 ems will highlight how physical modelling can clarify mechanisms of failur
 e for the cases shallow and deep foundations.\n \nThe lecture will end by 
 raising some philosophical questions relating to earthquake induced soil l
 iquefaction. Do individual grains lose contact during liquefaction? Will t
 his lead to opening of gaps/cracks in an intact body of soil? What happens
  to the soil in that state if it is subjected to shearing? Can the soil be
 low buildings really turn into ‘dangerous ground’?\n
LOCATION:Bristol-Myers Squibb Lecture Theatre\, Department of Chemistry
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