The RST Profile Monitoring System for Tunnel Concrete Segments is a series of tilt meters, fixed to the tunnel wall on each of the precast concrete segments erected in place as tunnel lining by a Tunnel Boring Machine (TBM). The system is based on the assumption that each concrete segment is a rigid body and that the complete ring deforms by rotation of the individual segments one relative to the other, and the rotation points are the contact surfaces between adjacent segments. This assumption is very often considered as acceptable by tunnel designers and reasonably close to reality, although spot checks using traditional convergence measurements or surveying methods should be conducted to confirm its validity for each individual tunneling circumstances. This Profile Monitoring System using tiltmeters is a simplified version of the Tunnel Profile Monitoring System (see separate data sheet) and its main advantage is that it can be deployed in the tight space available around the TBM, whereas the Tunnel Profile Monitoring System would be much more difficult to install in the same situation to monitor deformation. A data logging system and Geoviewer software (see separate data sheet) are available to provide near real time displacement and generate a graphical representation of the tunnel convergence.

The Profile Monitoring System consists of a series of precision bussed digital tiltmeters affixed on each of the concrete segments of a segment ring, including the key segment. Each tiltmeter is mounted on a base plate that allows for setting the vertical axis of the tiltmeter so that it will be suitably oriented when mounted on the concrete segment. Spatial displacement of the concrete segments results in changed tilt readings. The data logger system automatically collects the data and transmits it to a computer, either in near real time or by means of manual periodic data transfer using a laptop computer or a memory storage device. The computer then analyzes the data, and calculates the displacement profile for presentation.

The system is available in either open or closed loop configurations. The closed loop method is analogous to conventional closed end survey techniques, while the open loop must be referenced to a known location.

RST Instruments Ltd., 11545 Kingston St., Maple Ridge, BC, Canada V2X 0Z5, Tel.: 604-540-1100, 1-800-665-5599, +1-604-787-9673, e-mail: info@rstinstruments.com