Noise & Vibration case study

Tunnelling noise & vibration solutions

Background

The Crossrail project includes 21km of bored tunnel under the most densely populated parts of London. During the construction of the HS1 project, residents complained about noise and vibration from the Temporary Construction Railway within tunnels. To prevent the same thing happening on Crossrail stringent acoustic criteria were placed on the project.

Challenge

During construction a rail track was needed to service the Tunnel Boring Machines (TBM’s). Whilst the finished track is of the highest quality and mitigates vibration issues at source, this track would be damaged during construction. Therefore, a temporary construction railway had to be installed for the duration of construction. The obvious solution to mitigate the risk of noise and / or vibration complaints was to isolate the entire temporary track, but this would have been very expensive. Our challenge was to develop a solution to mitigate risk of complaints and save our client money.

Solution

We worked closely with multiple stakeholders including one of the other tunnelling contractors and their acoustic consultants plus the consultant engineers from Crossrail to develop a methodology to accurately predict tunnel vibration to the properties at the surface. We also collaborated successfully with the noise teams in all the affected boroughs, Tower Hamlets, Newham, City of London and Canary Wharf, to ensure their needs and the needs of their residents were met at all times.

We developed a bespoke piece of software to model the scenarios, building on all the available engineering knowledge. The software was calibrated and validated by measuring the actual vibration within the tunnels and at the surface simultaneously and feeding this data back into the model. The ground-breaking work we did has resulted in a new level of accuracy for the prediction of vibration from temporary railways at the surface. We were able to identify specifically which properties along the route were at risk.

This meant we could specify precisely where vibration isolation was required and where a ‘basic’ track could be used. Our work meant our client could re-use a ‘basic’ track from a previous project for the majority of the scheme; this saved hundreds of thousands of pounds. We then used our skill, experience and judgement to provide a cost effective solution for locations where problems were predicted. No time was lost due to noise or vibration issues which meant the critical time line was maintained.