Oct 21, 2021

Can ShapeArray™ and piezometers install into the same borehole?

Tyler Morency
1 month ago

Can ShapeArray™ and piezometers install into the same borehole?

As pore pressure has a direct relationship with the subsurface movement behaviours in soil, it should be no surprise that piezometers are used frequently alongside ShapeArray to monitor deformation. Can ShapeArray be installed into the same borehole? Members of Measurand’s technical service team receive that question frequently.  

Installation of ShapeArray and Piezometers 

The short answer is no. The installation of a piezometer into the same inclinometer casing is not recommended. The best practice recommended is for the instruments to be installed into separate boreholes. While both types of instrumentation require borehole installation, there is a number of reasons why these sensors can’t be installed into the same casing or borehole. 

ShapeArray’s patented cyclical installation 

SAAV‘s patented off-the-reel cyclical installation enables direct installation into new and existing inclinometer casings. SAAV’s joints are held into compression with the sides of the casing by a spring box assembly and locked into place with a casing cap. Anything within that inclinometer casing—the cable for a piezometer for example—can potentially obstruct the fit which potentially could impact the tilt readings of the SAAV’s MEMS sensors, and the deformation data by extension.  

Part of SAAV’s versatility is that it can also be installed vertically into PVC conduit to measure deformation. Robert Praeg, geotechnical instrumentation specialist, E.I.T., with Measurand’s technical services says that this method allows clients to install piezometers very close by to compare both sets of data within the area of interest.  

Piezometer installation 

There are several different types of piezometers (open and closed circuit) with different methods of reading data and sensor technologies. However, some of the most commonly used piezometers alongside ShapeArrays are vibrating wire piezometers. The best practice for the installation of vibrating wire piezometers is to fully grout them into a borehole with sensors placed at different elevations which allows pore-pressure measurements along the total length. 

Data collection methods for ShapeArray and Piezometers 

For situations where ShapeArray and Piezometers are located within the same area of interest to monitor pore pressure and deformation, Robert recommends an automated data acquisition system that can integrate readings from both sensors. He recommends the RSTAR system with a FlexDAQ by RST Instruments. In situations where several ShapeArrays are installed, Robert explains that with DTSAA, clients can wirelessly automate data collection to FlexDAQ as a central hub. 

“The alternative being, multiple different hubs or you’re running cable underneath the soil,” Robert says. “But as you can imagine running and trenching a lot of cable and protecting with an added conduit can be quite time consuming, which almost defeats the value that ShapeArray provides—easy installation.” 

A picture versus video footage 

Ground movement, in many cases, is relative to pore pressure, Robert explains. An advantage of automated monitoring, he continues, is having the ability to compare two continuous streams of data to reveal more information about the project site. His example is a Department of Transportation project in the Midwest that collects accumulated precipitation data to evaluate alongside ShapeArray data to see if movement occurs during rain.  

A helpful analogy to imagine the difference between seeing pictures of a sporting event in a newspaper versus watching a broadcast of the game in near real-time.  

A slide showing a manual inclinometer data point along with ongoing ShapeArray data from his recent short course presentation at GeoNiagara 2021 

“You’re using your imagination almost to visualize what is happening in between and with this instrumentation, bridging the gap from the unknown to the known. Without that, if you’re getting the snapshots, it forces the designer to make a much more conservative approach to mitigate any risk of what could be the unknown: is there a slip failure surface in this area that we don’t know about?” Robert says. “Whereas, with more information, you’re able to ideally, put fewer resources into a conservative approach because you’re able to actually measure exactly what’s going on.” 

Talk to an expert about deformation and pore pressure monitoring today 

  • 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