Jan 19, 2021

The top three things to consider when choosing ShapeArray vs an in-place inclinometer

Shane Spinney
4 months ago

The top three things to consider when choosing ShapeArray vs an in-place inclinometer

There is no cut and dried way to determine if a project’s deformation monitoring needs can be met with ShapeArray or an in-place inclinometer (IPI). However, we have outlined some considerations you should keep in mind when you are selecting deformation monitoring instrumentation, specifically ShapeArray.

The three key considerations to determine if ShapeArray is the right geotechnical instrument for your project are:

  1. Monitoring requirements
  2. Site conditions
  3. Casing specifications

What are the monitoring requirements? 

What are the sensor spacing specifications?
One of the first things that should be considered, especially in horizontal settlement monitoring, is sensor spacing requirements. ShapeArrays can meet a variety of spacing requirements including 250 mm, 500 mm, and 1 m gauge lengths depending on the monitoring application.

What length of instrument is required?
How long is your borehole or the zone of interest? This will ultimately determine the length of the instrument you require. 

Do you have a defined zone of interest? 
Depending on your monitoring application and where you expect to see movement, ShapeArrays provide many options for accommodating the right sensorized length to get the data you need. 

What is the expected movement? 
How much movement are you expecting to see? This will help determine the best-sized casing and evaluate the potential re-usability of the instrument on other projects. If you are expecting to see a lot of movement, this can impact the lifespan of your instrument and interrupt data collection. ShapeArray is flexible and can withstand greater degrees of deformation than traditional in-place inclinometers, which in specific applications is beneficial.  

What is your data collection interval?
In other words, how often do you need to record data? ShapeArray provides many options for automated data collection at various intervals from daily, hourly, or even faster depending on your application and logging configuration.

What is the length of your project?
How long is your monitoring program and at what stage in the project does it fall? ShapeArrays (SAAV and SAAX) can be installed for long-term monitoring, such as landslide monitoring, or short-term projects, such as urban construction. In many of these applications, clients can recover and reuse ShapeArray in other projects.

Site considerations

What are the site conditions of the installation? 
The ShapeArray’s design consists of rigid stainless steel sensorized segments connected by flexible joints. It is durable and allows for simple installation from its shipping reel in many applications. However, there are factors on-site that should be accounted for when planning to install ShapeArray. 

Where will the instrument be installed? 
Although ShapeArray is simple to install, depending on the location of the installation, you may need to ensure other worksite factors are dealt with. For example, as we can see in the image here of workers installing a ShapeArray under a roadway, the road needed to be shut down while the trench was excavated and the instrument installed.

What are the geotechnical properties of your site? 
Details such as soil conditions, expected locations of movement, and whether the instrument will be underwater will all factor into your installation plan and requirements for a successful monitoring program.

What kind of temperatures are you expecting on-site?
Temperatures at the time of installation and during operation of the instrument are important to consider, especially if water freezing will be a consideration. ShapeArray software provides temperature corrections when operating in temperatures of -35°C to 60°C, polynomial temperature algorithm corrected.

At what angle, relative to gravity, is your installation?
This is an important consideration due to how ShapeArray’s MEMS accelerometers work. For installations that are mostly vertical relative to gravity, ShapeArray will produce very accurate 3D data. In cases where the instrument is nearly horizontal, ShapeArray will produce 2D settlement data only. 

Casing specifications

ShapeArray must be installed in casing regardless of the orientation of the instrument or the monitoring application. A wide variety of casings and conduits can meet this requirement, including standard grooved inclinometer casing.

What type and inner diameter of casing are you using?
Specifically, what is the inner diameter of that casing? For vertical applications, we support a wide range of casings from:

  • 1” trade dimension Schedule 40 PVC conduit (~27 mm ID) 
  • Standard inclinometer casings with 70 mm or 85 mm ODs (59 mm and 73 mm IDs respectively) 
  • Any casings with an ID ranging from 47 mm to 100 mm, including existing IPI casings.

For horizontal applications, the type of casing required will depend on the horizontal application and the amount of loading expected. Casing ovalization due to loading must be a consideration when selecting casings for horizontal applications. Typically, applications will use a 2” trade dimension Schedule 80 conduit.

For convergence monitoring, ShapeArray ships from the factory already enclosed in a flexible conduit for ease of installation. 

What is the condition and/or shape of the casing?
In many cases, clients can install ShapeArray directly into existing casings on site. In some cases, these casing may have preexisting deformation. This deformation may inhibit the ability to install traditional geotechnical instruments that are more rigid.

Ex. retrofitting inclinometer casing where a manual probe can no longer be used.

If you plan to retrofit some existing casings, you need to have a sense of the existing condition and shape of that casing to ensure your ShapeArray installation is successful. 

Do you know the exact length of your casing? 
Clients should know the full length of the casing prior to ordering ShapeArray. Knowledge of the casing length combined with a good understanding of the zone of interest for monitoring will greatly affect the length of ShapeArray required to meet your monitoring needs. 

An understanding of the zone of interest helps us determine the sensorized length required and whether your planned ShapeArray installation requires any silent segments or extra extension tubes.  

Have any other questions?

Speak with a member of Measurand’s technical services team.

  • 1993

    The Beginning

    Measurand is established in Fredericton, New Brunswick
  • 1994

    Bend sensor development

    Measurand develops and patents fiber optic bend and position sensors for the medical and automotive sectors

    U.S. Patent 5,321,257

  • 1995

    Canadian Space Agency

    Receives funding from the CSA to develop sensor technology that ultimately leads to invention of ShapeTape

    U.S. Patent 5,633,494

  • 1999

    Patent on fiber optic sensor

    Measurand receives patent for "Fiber Optic Bending and Positioning Sensor" issued June 29, 1999

    Canadian Patent 2,073,162

  • 2001

    ShapeTape & ShapeHand debut

    Measurand designs and develops innovative motion capture technology

    U.S. Patent 6,127,672, 6,563,107

  • 2002

    Measurand Attends the ICPMG

    First contact with the geotechnical sector at the International Conference on Physical Modelling in Geotechnics (ICPMG)
  • 2004

    ShapeArray

    Design patent application sent about a new product designed to meet the specific needs of the geotechnical industry

    U.S. Patent 6,127,672, 6,563,107

  • 2005-08

    ShapeWrap

    Measurand debuts ShapeWrap motion capture technology for the film and animation industry

    U.S. Patent 7,296,363

  • 2006

    Malibu installation

    ShapeAccelArray installed for ground monitoring for the first time​ in Malibu, CA

    Canadian Patent 2,472,421

  • 2007

    ShapeMRI

    Suite of instrumentation developed for motion capture within Magnetic Resonance Imaging (MRI) machines

    U.S. Patent 7,296,363

  • 2011

    SAAScan launched

    Built for rapid deployment and repeated use

    Canadian Patent 2,472,421

  • 2014

    SAAX launched

    Purpose-built for heavy-duty horizontal installation

    Canadian application 2,815,199 & 2,815,195

  • 2017

    SAAV launched

    The only geotechnical instrument with a patented cyclical installation method

    Cyclical Sensor Array, Canadian application 2,815,199 & 2,911,175