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SUMMARY:Distributed fibre optic strain measurement of geotechnical structu
 res. - Hisham Mohamad\, CUED
DTSTART:20071123T163000Z
DTEND:20071123T173000Z
UID:TALK8333@talks.cam.ac.uk
CONTACT:Zelda Stuck
DESCRIPTION:In practice\, forces calculated in geotechnical structures whe
 re the structures interact with soil such as piled foundations and tunnels
  are not fully understood due to complexity of deriving actual loading con
 ditions and boundary value problems. Measuring complete strain regime acro
 ss the whole length of these structures is one of the ways to check how th
 e structures are actually performing under various loading conditions and 
 hence validate assumptions made in design. An innovative technique based o
 n optical fibre sensing that allows such distributed strain measurement ha
 s recently been introduced in structural health monitoring known as Brillo
 uin Optical Time-Domain Reflectometry (BOTDR). The distributed optical fib
 re sensing allows measurement of strain along the full length (up to 10km)
  of a suitably installed optical fibre. In the context of monitoring strai
 n in piled foundations\, retaining walls and tunnels\, capturing the conti
 nuous strain profile is often invaluable to pinpoint localised problem are
 as such as joint rotations\, cracks\, deformations and other non-uniformly
  distributed soil-structure interaction loads.\n\nAs BOTDR sensing is prac
 tically new in the field of monitoring underground infrastructures\, vario
 us key issues are examined before the technology can be said to be a fully
  developed tool. Some of the issues covered include best practice of insta
 llation / attachment techniques\, type optical cables\, robustness\, accur
 acy of measurements and data processing / interpretations. \n\nThe researc
 h focuses on developing BOTDR technology for application to piled foundati
 ons and tunnels by deploying the sensors on real construction sites. Two c
 ase studies of tunnel-tunnel interactions in London and Singapore are pres
 ented followed by two examples of pile instrumentations of high capacity l
 oad bearing pile and laterally loaded secant-piled wall both in London. Se
 veral important findings from laboratory works are included to validate th
 e instrumentation techniques conducted in the field sites.\n
LOCATION:Engineering Department - LR6
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