Noise and vibration monitoring duringCrossrail tunnelling under the Barbican

I have to admit I was excited; in a geeky kind ofway. Who else gets the opportunity to have theBarbican concert hall all to themselves for thenight? Okay, so it was 1.10am on a Wednesdaymorning and we were here to work. Andmaybe, just maybe, we would hear Elizabethsteadily grinding her way 30m beneath us.

Elizabeth was the first of DSJV Tunnel BoringMachines (TBMs) to make her way eastwardson her final leg of this Crossrail project toFarringdon. We were in the Barbican tomeasure any vibration and listen for anyaudible signs of her coming through. Heroriginal path involved cutting through some ofthe Barbican piles. If this happened it wouldlead to the complication of the tunnel lininghaving direct contact with the piles for theBarbican. This would create an easytransmission route for vibration, potentiallyresulting in tunnelling works (and evenpossibly the operational train) being audible inthe Barbican. This would mean the contractor

had not met the stringent design aims fornoise and vibration for the concert hall.

Elizabeth passed quietly underneath us. Guess she found a path through those pilesafter all. Back in the office in the daylight, weanalysed the data collected. Yes she was there, the vibration traces through our highlysensitive accelerometers picked her out.

The next potential problem would come fromthe train using the temporary track to supplythe TBM with concrete rings and remove thespoil waste.

The data confirmed the accuracy of ourbespoke prediction model (the first of its kind)and our recommendations on the choice oftrack design used. The accuracy of ourpredictions regarding track type allowed ourclient to achieve considerable cost savings.

Gillian Whyman – Acoustic ConsultantSRL Technical Services

SRL Services

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