The Use of Shape Accel Array for Monitoring Utilities during Urban Tunnel Drives

Third party asset protection is an area of critical importance to the success of Crossrail as a project. For this reason, a vast amount of monitoring systems are being employed across London to ensure that potential ground movements caused by Crossrail works are understood and monitored so that appropriate actions can be taken should unexpected movements occur. This paper will focus on the monitoring of the Ranelagh Sewer, a Victorian brick sewer located approximately 230 m east of the Royal Oak Portal – the launch site for the C300 Western Running Tunnels.

The Drive X Western Running Tunnels have been launched in sequence from the Royal Oak Portal (west of Paddington Station) and are boring eastward toward Farringdon Station, passing by Paddington, Bond Street and Tottenham Court Road Stations on the way. The tunnels are being excavated by a Tunnel Boring Machine (TBM) using Earth Pressure Balance Mode (EPB) as a control mechanism to reduce potential ground surface movements. Each tunnel has an excavated diameter of 7.1 m, although the concrete lining of the tunnel will only have an external diameter of 6.8 m. Although EPB method of tunnelling is designed to reduce ground movements as much as possible, movement is still expected and hence provisions must be made for third party assets that may be affected by this movement.