Measurand’s SAAV can be used to monitor convergence in a section of tunnel. For convergence monitoring, the SAAV is shipped from the factory in a flexible PVC covering that can be mounted directly to the surface of the structure to be monitored without the need for extra conduit. When selecting an SAAV for convergence monitoring, it is important to choose an appropriate segment length. The appropriate segment length is determined by the radius of the tunnel cross section to be monitored:

  • 500 mm segments for tunnels with radius of 3 m or greater
  • 250 mm segments for tunnels with radius of 1 m or greater
WARNING: In some cases, tunnels are considered to be explosive atmosphere (ATEX) environments. Certain ShapeArray products are certified for use with EX ’d’ Flameproof protection in areas classified as Zone 1 or Zone 2 in accordance with European Directive 94/9/EC when installed in compliance with the ATEX Workplace Directive 1999/92/EC. Existing certification is only valid in Europe. Exact requirements for proper usage should be discussed with Measurand, all certification authorities, and the end user before ShapeArray is installed in any hazardous location.

NOTE: Measurand highly recommends that users perform a complete diagnostics test on their ShapeArray prior to installation to ensure the instrument is working properly. The .TXT report file generated should be included with the installation log for record keeping purposes. A complete diagnostic report from the time of installation could be required to advance warranty claims should an issue occur in the future. 

Step 1 - Position the SAAV Reel in the Structure to be Monitored

Measurand SAAVs can be installed from the factory supplied reel directly to the surface of the structure being monitored for convergence. Place the reel so that the SAAV unreels towards the surface of the structure to be monitored. The reel can be positioned such that the SAAV rolls off the top or the bottom of reel.

Step 2 - Attach the First Segment to the Structure

Unreel the SAAV and secure the first segment to the structure. Measurand recommend using one of the larger U-clamps included in the installation kit. Although Measurand recommends using U-clamps, properly sized P-clamps or other user-provided hardware is acceptable.

Figure 1: An example of the U-clamps included with the installation kit for installing SAAV for convergence monitoring

WARNING: When installing a ShapeArray in convergence, care must be taken to keep the entire length of the ShapeArray within the same vertical plane. Deviations of the instrument beyond 10° of the vertical plane will negatively affect the shape calculation for the instrument.

Step 3 - Continue Unreeling SAAV and Attaching Segments to Structure

Using the smaller U-clamps provided in the installation kit, continue carefully unreeling the SAAV and securing each segment to the surface of the structure. Ensure only one clamp is used per segment. Clamps must be offset approximately 5 cm (2") from the bendable joints between the SAAV's segments.

WARNING: Clamps should never be place right on the bendable joint between segments when installing SAAV for convergence monitoring. The joints must be completely free to bend for accurate results to be reported.

Figure 2: Position reel with the SAAV coming off towards the surface of the structure and secure each segment

Step 4 - Tighten the Set Screws and Route Cabling to the Data Acquisition System

Once the SAAV has been completely attached to the surface of the structure, the set screw and cable gland in the fittings at the cable end of the SAAV need to be tightened. The communication cabling can then be run to the data acquisition system.

NOTE: Some amount of cabling near the top of the SAAV should be reserved to provide strain relief.