Southdowns was the lead noise and vibration specialist for the design and build contractor (Alstom TSO Costain JV) with responsibilities that included the final detailed design sign-off of the proposed Standard Track Systems, and the Testing and Commissioning of the Tunnel Ventilation System for the Central Tunnels section of the Crossrail alignment under central London.
The track was designed to achieve prescriptive groundborne noise and vibration requirements in overlying buildings and included several generic trackform types including: resilient baseplates; bi-block and monobloc booted sleeper systems; and two variants of floating slab track (FST) in sensitive locations. Other design related elements included: the optimisation of fixed nose switch and crossing units to minimise groundborne noise and vibration; the field measurement of vibration transfer functions between tunnels and buildings; the research, development and management of combined wheel / rail roughness to control groundborne noise and vibration; and calculation of Insertion Gains to assess the predicted changes in track system parameters associated with design changes. The work package also included liaison with Local Authorities on technical matters to ensure that Project commitments are achieved and also to interface on issues with the future Infrastructure Maintainer.
Southdowns was responsible for the construction noise and vibration management during track construction and M&E fit-out. This included: groundborne noise and vibration assessments of the temporary track laying trains in tunnels; FST construction using high density concrete pumping via shafts from the surface; preparation of and submission of Section 61 consent applications, dispensations and variations; routine Best Practicable Means audits and attended monitoring; vibration risk assessments and monitoring the effects on heritage assets.
Over a period of over 2 years, Southdowns was tasked with planning and implementing an accelerated programme of testing and commissioning surveys at each of the 18 ventilation shafts along the tunnelled section of the route. Working closely with the M&E designer, the ATCjv delivery team and the Project Manager Crossrail Ltd, Southdowns specialists were tasked with designing a compliance methodology that could be used for sites where target noise levels were expected to be significantly below background noise levels at receptors. This involved the application of near field measurements in combination with airborne noise propagation Transfer Functions compiled from the main acoustic design models. A campaign of detailed investigative surveys were undertaken at some sites where the need for rectification measures was identified. Southdowns led the activities necessary to trouble-shoot certain sites under certain modes of operation of the TVS, and assisted in assuring the design and specification of additional control measures where these were required.
“Southdowns Environmental Consultants are highly valued advisors to ATCjv on the Crossrail C610 contract. They have always acted professionally and are well respected in their field of expertise. They have consistently delivered to a high standard and have helped us successfully overcome several technically complex and politically sensitive challenges.” – ATCjv Engineering and Integration Manager
