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SUMMARY:Engineering in Sediments  - Prof. Malcolm Bolton\, Geotechnical an
 d Environmental Research Group
DTSTART:20121029T170000Z
DTEND:20121029T180000Z
UID:TALK39402@talks.cam.ac.uk
CONTACT:Lois Salem
DESCRIPTION:Our civil infrastructure of buildings\, roads\, railways\, tun
 nels and pipelines is mostly carried on\, or within\, uncemented sediments
 \, i.e. soils. Such soils may be mapped by a geologist as “solid” such
  as the Gault clay or London clay\, or “drift” such as the Fenland sil
 ts or the terrace gravels. They may even be artificial\, such as embankmen
 ts or simply urban detritus. The geotechnical engineer is taught to treat 
 them on their own merits as a melange of ceramic fragments which represent
  our cheapest construction materials. They are taught to classify them and
  test them mechanically with a view to substantiating design calculations 
 which are intended to ensure that whatever soils are encountered on the si
 te of a project\, they should more or less “stay put” after constructi
 on\, continuing to support the facility for perhaps a human lifetime. Geol
 ogists take a broader perspective in time and space and become aware that 
 soils\, and even rocks\, endlessly transform and shift around\, whether ma
 n intervenes or not. They learn of all the natural influences –  tectoni
 c\, gravitational\, fluid\, thermal\, chemical and biological –  that ca
 use all this transformation and mobility. Geologists know that a human lif
 etime is a pathetically short period\, and that the apparent permanence of
  our facilities is illusory.\n \nThese differences in perspective lead to 
 difficulties in communication and comprehension when geologists try to ass
 ist engineers in the planning and execution of large projects. But all kno
 wledge can be valuable\, if its significance can be recognised. The talk w
 ill introduce two geotechnical issues that illustrate the need for enginee
 rs and geologists to be better aware of each other’s discipline. First\,
  there is the question of the mobility of pipelines laid on the deep ocean
  bed for the purposes of recovering oil from even deeper reservoirs. Here\
 , engineers would do well to have considered the possible practical implic
 ations of bioturbation in the formation of these clay sediments. Second th
 ere is the issue of the mobility of clay slopes\, variously referred to in
  geological literature as solifluction or slope creep\, which can affect n
 atural slopes\, cuttings or embankments. Here\, geologists would benefit f
 rom knowledge of the critical state friction angle\, and its role in marki
 ng the boundary between conditions which are stable and unstable. These il
 lustrations may provide the grounds for some continuing discussion and deb
 ate.
LOCATION:Harker Room 1\, Department of Earth Sciences
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