Feb 16, 2022
Measurand’s SAAV is the most versatile ShapeArray available, and thanks to its rugged joint design, generous bend radius, and narrow diameter, Measurand’s SAAV ShapeArray can be safely and reliably installed where traditional inclinometers cannot.
Measurand’s patented cyclical installation method allows for direct insertion of SAAV into a range of casing sizes and widths, including both standard grooved inclinometer casings and smooth casing types, without the need for assembly in the field.
Designed to be as versatile as possible, SAAVs can be installed vertically, horizontally, or in an arc in order to capture real-time deformation data quickly and efficiently, saving both time and money.
Many clients use SAAV in vertical installations for subsurface lateral movement monitoring applications, rather than an In-Place Inclinometer because of SAAVs ease of installation and higher spatial resolution. Also, because SAAV can be installed into a range of standard inclinometer casings, SAAV is ideal for retrofitting existing geotechnical monitoring infrastructure—even into damaged and deformed casing.
However, SAAV’s versatility means the instrument can also install into more narrow diameter, conduit-style casings that are easy to source and are low-cost. Unlike traditional inclinometer casings that must be ordered from geotechnical instrumentation suppliers, conduit-style casings can be sourced from local hardware stores.
Once you’ve decided to work with Measurand to use ShapeArray’s real-time deformation capture as part of your monitoring strategy, you’ll then need to decide which type of casing will work best for your project. Below, we’re looking at which casings work best for vertical applications.
When choosing a casing size, you need to consider how large your shear zone will be and how much deformation you expect to observe.
Smaller casings offer an incredible amount of precision. If you expect less than 20 mm of deformation, a smaller casing will enable the SAAV to detect and report even the tiniest movement more accurately.
When monitoring larger areas, where movement happens over a larger overall span (with slope stability monitoring, for example), a larger casing will survive longer due to the breadth of the deformation spread. Smaller casings are more appropriate for things like structures or retaining walls, where large movements are not likely.
Of course, smaller casings can withstand only so much deformation before the risk of damage to the instrument. A larger casing—an inclinometer casing, for example—means more instrument longevity, especially when deformation is intense and localized. In the end, casing size selection comes down to what kinds of deformation you expect and how large you expect the deformation zone to be.
After size, the next major consideration will be the material of your ShapeArray casing. There are advantages to both metal and plastic casings, and the right choice ultimately depends on the particulars of your project.
With surface-mounted ShapeArray installation (such as with a retaining wall or similar structure), a metal pipe is the better choice over plastic because you can expect very little deformation. Retaining walls for example are incredibly rigid, and so a rigid casing gets the job done nicely. Of course, when you’re dealing with less rigid materials such as soil or sand, the flexibility of plastic is preferred. Compared to the rigidity of metal (which has been known to snap under high degrees of deformation), plastic casings will survive longer in the ground and offer unparalleled flexibility.
Plastic also offers chemical stability, resisting the damage of oxidization that metal casings might suffer. Skip the rust and corrosion by going with plastic.
Next, you’ll need to decide what type of plastic you’re going to use for your SAAV casing. For decades, PVC (or Polyvinyl Chloride) has been the go-to material because of its high performance and versatility coupled with its low cost. In recent years, however, the material has been banned in some countries due to the environmental consequences of its fabrication and use. If you’ve decided on a plastic casing but are unable to source PVC, PE (or Polyethylene) will serve as a perfect substitute, as it offers similar flexibility and performance without the environmental runoff. PE is lightweight, easily processed, and offers near-zero moisture absorption, with high chemical and impact resistance and a low coefficient of friction, making it a sound choice. Although the casing material is different, make sure to check the wall thickness of the casing. If you choose a thin wall section, the casing will be more likely to crack under pressure. The right casing will help you prevent the intrusion of foreign materials such as soil and water, prevent freezing, and limit the need for instrument repair or replacement in the field.
The right casing for your vertical ShapeArray installation depends on several factors—specifically what kind of deformation you expect to measure and where combined with the availability of locally-sourced materials.
Measurand’s technical services team can help you choose the correct casing size and type based on the project’s requirements.