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SUMMARY:A Constitutive Model for Locally Drained Shear Bands in Globally U
 ndrained Dense Sand - Hansini Mallikarachchi\, CUED
DTSTART:20191024T150000Z
DTEND:20191024T154500Z
UID:TALK129865@talks.cam.ac.uk
CONTACT:Magdalena Charytoniuk
DESCRIPTION:When saturated granular materials which are dilative in nature
  are subjected to the undrained deformation\, their strength increases due
  to the generation of negative excess pore pressure. This phenomenon is kn
 own as dilative hardening and can be witnessed in saturated dense sand or 
 rocks during very fast loading. However\, experimental evidence of undrain
 ed biaxial compression tests of dense sand shows a limit to this dilative 
 hardening due to the formation of shear bands. There is no consensus in th
 e literature about the mechanism which triggers these shear bands in the d
 ense dilative sand under isochoric constraint. The possible theoretical re
 asoning is the local drainage inside the specimen under the globally undra
 ined condition\, which is challenging to be monitored experimentally. Henc
 e\, both incept of localisation and post-bifurcation of the saturated undr
 ained dense sand demand further numerical investigation. Pathological mesh
  dependency hinders the ability of the finite element method to represent 
 the localisation without advanced regularisation methods.\n\nThe aim of th
 is study is to provide a macroscopic constitutive behaviour of the undrain
 ed deformation of the saturated dense sand in the presence of a locally dr
 ained shear band. Discontinuation of dilatant hardening due to partial dra
 inage between the shear band and the adjacent material is integrated into 
 the constitutive model without changing governing equilibrium equations. I
 nitially\, a classical bifurcation analysis is conducted to detect the inc
 eption and inclination of the shear band based on the underlying drained d
 eformation. Then a post-bifurcation analysis is carried out assuming an em
 bedded drained or partially drained shear band at gauss points which satis
 fy bifurcation criterion. \nThe smeared shear band approach is utilised to
  homogenise the constitutive relationship. It is observed that the dilatan
 t hardening in the saturated undrained dense sand is reduced considerably 
 due to the formation of shear bands.
LOCATION:CivEng Seminar Room (1-33) (Civil Engineering Building)
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