Shape arrays are advanced inclinometer-like instruments used for monitoring settlement, movement and vibration.

Common uses

Monitoring movement eg retaining wall movement, tank bases, sewers
Slab heave and settlement
Drill positioning
Vibration monitoring
Differential settlements during tunneling or jet grouting operations
Subsurface movements in landslide areas, highway cuts, and embankments

Process

A shape array is a chain of rigid segments connected by flexible joints. The joints are designed to resist twist but allow the segments to tilt in any direction.

Shape arrays can be installed in a variety of ways:

  • Installed in existing inclinometer casings to automate readings
  • Inserted into small diameter pipe and installed directly into boreholes
  • Fixed to tunnel linings or concrete slabs

Each segment is instrumented with three orthogonally mounted tilt sensors and a microprocessor. The microprocessor calculates the XYZ position of the segment based on length of the segment and measurements from the tilt sensors. The overall shape of the array is found by cumulating the XYZ positions of the connected segments.

Initial measurements serve as a baseline. Subsequent measurements, obtained at regular intervals, are compared to the baseline. Changes indicate that deformation has occurred and reveal the direction and magnitude of deformation.

Shape array measurements are forwarded to our  automated monitoring platform which processes the measurements, checks for alarms, and posts plots and planviews on the project website 24/7.

Advantages

  • High accuracy: Sensors and interfaces provide low noise, high precision, digitised measurements. Accuracy of 1.5m for every 32m SAA.
  • Quick and easy to install: The SAA sensor can be inserted in a tight fitting PVC tube and held in compression to work. Once released, it can be pulled out and reeled back on its storage drum for reuse.
  • Reliable: The rugged SAA sensor string is designed to be used in all fields of construction. The steel outer mesh provides protection while its rigid articulated segment chain design makes the SAA a sensor that can be used in most harsh environments.  
  • Robust: Wireless sensors and nodes can operate at temperatures from -40°C to +60°C.
  • Intelligent: Segments can be disabled so that all relevant segments can feed raw data into an automatic processing protocol which distributes engineering displacement data to GEO-Instruments monitoring platforms.