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SUMMARY:Pipeline uplift resistance in cohesionless soils: a physical-model
 ling oriented approach - Junkan Tony Wang
DTSTART:20111202T160000Z
DTEND:20111202T170000Z
UID:TALK33153@talks.cam.ac.uk
CONTACT:Anama Lowday
DESCRIPTION:Offshore pipelines are often buried by ploughing or water-jett
 ing in order for physical protection and thermal insulation. Upheaval buck
 ling (UHB) is a common design issue for buried offshore pipelines when the
  out-of-straightness of the pipeline\, combined with the high axial compre
 ssive forces induced by the extreme operating conditions\, causes the pipe
 line to buckle upwards. The soil cover backfilled on top of the buried pip
 eline serves to provide resistance to UHB. The required pipe upward moveme
 nt\, or mobilisation\, to achieve the desired uplift resistance from the s
 oil cover is a vital design parameter\, in that the structural integrity o
 f the pipeline under operating conditions relies upon it. Currently\, the 
 DNV-RP-F110 is the most commonly used code by practicing engineers worldwi
 de to address UHB in design. However\, its provisions on uplift resistance
 \, particularly on the mobilisation side\, can be misleading.\nThe main ar
 eas that have been investigated in this research are: mobilisation distanc
 e\, uplift resistance at low covers (cover:diameter ratio\, H/D\, < 1)\, a
 nd scaling laws in centrifuge modelling. The talk presents the results fro
 m 34 physical model tests on pipeline uplift resistance in cohesionless so
 ils\, including 8 full-scale tests in saturated loose sand\, 10 full-scale
  tests in dry gravel\, and 16 centrifuge tests in saturated dense/loose sa
 nd. Cover heights in the full scale tests are up to 0.35m in sand and 0.6m
  in gravel. The pipe-soil interaction mechanisms\, obtained from displacem
 ent- and strain-based PIV data\, will be shown for both the full-scale and
  centrifuge tests. Comparison between centrifuge data and full-scale data\
 , i.e. modelling of physical models\, will also be presented to illustrate
  the limitation of centrifuge scaling laws on mobilisation.\n
LOCATION:Engineering Department - Lecture Room 6
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