Noise and vibration from TBM tunnelling
Managing noise and vibration during tunnelling will be based on a best practice approach as undertaken by Metro Tunnel’s contractors on similar projects around the world.
A project of the size and scale of the Metro Tunnel Project cannot be built without some impact on the surrounding area. We are committed to minimising the impacts of construction and operation of the new twin tunnels as much as possible.
The Metro Tunnel Project is being delivered in accordance with strict Environmental Performance Requirements (EPRs) that apply for construction and operation of the new twin tunnels. The amount of vibration and ground-borne noise that may occur at properties located near the path of the tunnel boring machines (TBMs) must comply with the EPRs.
Ground-borne noise is noise heard within a building that is generated by vibration transmitted through the ground into a structure. It is often referred to as ‘regenerated noise’. Groundborne noise is measured by a sound meter.
Prior to tunnelling, comprehensive geological testing and environmental assessments are undertaken. Property condition surveys will be offered to properties based on an environmental assessment.
Managing noise and vibration during tunnel construction
During construction, vibration is generated by the operation of the TBM as it digs through the ground. The level of noise and vibration generated will depend on the ground conditions. It is not possible to completely eliminate vibration generated by the TBMs as they build the twin tunnels.
The level of ground-borne noise that may be heard in a building depends on its type and its proximity to the tunnel alignment. Individuals experience noise and vibration differently and low-levels of noise and vibration may be audible and experienced as the TBMs pass directly under a property. At night, when the background noise level is low, works may be more perceptible.
Ground-borne noise and vibration levels will be monitored throughout construction to ensure all Project EPRs are met.
Following completion of tunnel construction and installation of the rail track, ground-borne noise and vibration will be measured to confirm the operational EPRs are met.
Residents and businesses located near tunnelling will be contacted by the Project team prior to TBMs approaching their property.
Managing noise and vibration during tunnel operation
When train services are running, vibration will be generated by the operation of the train on the tracks. The Project’s design achieves the ground-borne noise target of 35dB(A) across the alignment.