Webinar Q & A Transcript: Scourlok and Pyrawall Engineered Bank Stabilisation

Q: Is there some information available on the durability of the scourlok baskets, vs say a typical polymer coated gabion basket wire type solution. The reason for asking is that if the baskets do eventually disintegrate the gabion rocks and geotextile behind would remain, whereas with scourlok the soil will eventually wash away and the slope would start to erode? Probably general durability as compared to gabions. The difference I see is that with gabions rocks will remain when the baskets eventually disintegrate (which we know they will), whereas with Scourlok all that will remain is soil, but then maybe the vegetation is what eventually holds it all together?

A: SCOURLOK has superior strength and durability to withstand the most demanding environments. The SCOURLOK geosynthetics are inert to all naturally occurring chemicals. If needed, the steel baskets can be customized for use in more corrosive environments. This gives SCOURLOK a distinct advantage over PVC coated gabions. Once the PVC coating on the gabion is nicked, the metal beneath is subject to corrosion. It is important to remember, gabion performance is based on confining the rocks in the basket. Once the rocks spill out of the basket, the performance equates more readily to an unconfined riprap design. And if riprap had been the appropriate choice to control erosion, it most likely would have been chosen over the more expensive gabion. The break in the structure of a SCOURLOK basket does not have to be catastrophic. The SCOURLOK basket is draped with PYRAMAT on the outside and internally lined with a geotextile. The geosynthetics in combination will offer backfill confinement. The introduction of vegetation will make the system more stable.

Q: How much horizontal stress it can resist? How resistant this product is against cut & piercing?

A: SCOURLOK incorporates PYRAMAT on the outside of the baskets for protection against UV degradation, debris loading, and other non-hydraulic stresses. Being woven, the PYRAMAT resists tearing, and damage is usually localized to a small area. Vandalism can occur, but the fibers are so tenacious, that it frustrates would be vandals. The design of the SCOURLOK considers sliding and overturning resistance. Factor of safety for these two parameters is calculated to determine the suitability of the design against horizontal movement.

Q: Can scourlok be used with geogrid reinforcement to form a reinforced earth fill facing?

A: SCOURLOK can be used as the facing for geogrid reinforced fill. There are height limits to the number of baskets to be stacked. Please engage Propex or Global in your design of this type of system.

Q: The designs do not appear to include any aspects to prevent flanking behind the walls where dispersive or non-cohesive soils are present. How did you account for this risk?

A: The slides did not always show this well, but be assured, any SCOURLOK design will have a termination up and down stream that curves into the bank to prevent a stream flanking the ends. The burial depth of the SCOURLOK System will be dependent upon the site conditions. Please engage Global and Propex to help you with this crucial design element.

Q: Is there a maximum settlement tollerence for the pyrawall?

A: PYRAWALL, by design, is a flexible system. It will be able to tolerate differential settlement along its length by flexing and moving. During the design process, the parties involved will coordinate on the amount of settlement that can be tolerated. The selection of fill materials and construction procedures can help to minimize the settlement. Engage Global and Propex to help with this design.

Q: What is the warranty length of these products ie scourlok and pyrawall.

A: Propex products are designed for a 100-year life in normal conditions. The products are warranted against any manufacturing defects. As we do not install, we can only warrant the products and not the installation.

Q: What type of backfill materail (cohesive or grangular) is required? What is the efficiency if cohesive materail used as backfill for scourlock system?

A: The advantage of SCOURLOK is that on-site fill, whether cohesive or granular, is perfectly acceptable. During the design process, the type of expected fill is used to determine basket stack height and configuration. However, a high volume of high plasticity clay is not a good option for infill in the baskets. These soils are extremely susceptible to expansion when exposed to water. A survey of the locally available fill will determine the suitability and design of the SCOURLOK System.

If you have any further questions or would like further information please contact: andy@globalsynthetics.com.au

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