Jan 19, 2021
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:
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.
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.
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:
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.
Speak with a member of Measurand’s technical services team.