Q1. Can I use Platipus anchors in wet soil?
A.The short answer to this question is yes. Platipus anchors perform exceptionally well in most non-cohesive granular soils. Experience has shown that the anchors perform well even in water-saturated conditions in sandy clayey soil. If you are confronted with a situation where there is very saturated soil present, contact our AMT representatives and they will provide specific advice.

Q2. Is the Platipus anchor only useful for temporary works?
A. No, we can provide systems in materials that have a potential lifespan of 80 to 100 years, or more, in Australian conditions and the anchor will continue to function for as long as the anchor material is not corroded away

Q2.What kind of ground conditions can’t I use Platipus anchors in?
A. We advise our clients that Platipus anchors are not suitable for use in very silky saturated clay that has a platelet type structure. This material has virtually no shear angle that the anchor can build a frustrum cone upon. Note that in most circumstances, with this exception, clays do not represent a problem for Platipus anchors. If in doubt, contact your AMT representative for advice.

Also, while Platipus ground anchors can perform well in very weathered shale, they obviously cannot be embedded in rock.

Q3. Is the Platipus anchor only useful for temporary works?
A. No, we can provide systems in materials that have a potential lifespan of 80 to 100 years in Australian conditions.

Q4. Is the Platipus anchor an “active” or a “passive” anchor?
A. For all intents and purposes, this distinction is almost immaterial when used in conjunction with Platipus ground anchors. In short, the anchors can be both.

When the anchor is load locked under tension it is effectively “active”. After it is load locked into position and the top termination tightened, it becomes technically “passive”. The interesting attribute of the Platipus anchor is that, if after it is locked off there is further stress put on the anchor (e.g., movement in piling it is supporting), the anchor becomes “active” again. As the anchor is stressed due to movement, it further compacts the soil above it increasing the load it is carrying. This will continue until the physical limits of the soil and anchor system are surpassed and the anchor starts to pull free.

Q5. How long after I’ve installed a Platipus ground anchor can I connect it to the load I want it to hold?
A. Immediately. Once the anchor has been tensioned to the required proof load, it is ready to take its load.

Q6. How do I know what load an anchor I’ve installed is carrying?
A. The Platipus anchor system allows the use of a simple, in-line load cell (attached to the hydraulic jack) during the tensioning process that provides precise measurement of loadings.

Q7. Do I need to grout a Platipus ground anchor?
A. In short no – in 99% of cases. However, some clients may choose to grout or “sleeve” our anchors to ensure the lifespan they require in very aggressive soils. Contact your AMT representative for advice if this is an issue for your project.

Q8. How does the Platipus system, when used on civil engineering applications, compare to conventional ground anchoring systems in price?
A. In our Australian experience, we have generally found that at the conclusion of a project the Platipus system was the most cost-effective solution. We consider that the Platipus system often beats conventional systems in terms of price (even in circumstances where the initial project quotation seems to favour conventional systems) particularly in the following areas:

• The prevalence and size of contract variations – to date we’ve rarely had any.
• Project time – you’ll spend less time finishing the job and incurring all the cost associated with working on a site. This can improve business profitability in other ways. Why? Because Platipus anchors are immediately ready to take the required load and be put into service when installation is completed and you know precisely what load they hold. Grouted anchors, for example, can take 7 days to cure before they are ready to be load tested. Testing can be expensive. Further, if they don’t make the load required, additional anchors might need to be installed and consequently, another 7 days is required before the anchoring project might be completed. Platipus anchors minimise project ”downtime” and help ensure that managers meet critical deadlines.
• Greatly reduced chance of incurring liquidated damages – see above.
• Ask AMT for a quote on your project and hopefully when you take all project cost ramifications into account, we’ll be proved correct.

Q9. How does the Platipus anchor compare to other anchors based on similar design principles?
A. There is no other anchor of similar design on the market.

Some anchors have an essentially spherical design compared to Platipus’ conical shape. As a rule of thumb, a conical anchor will usually hold almost twice the load that can be carried by an anchor of spherical shape and similar surface area (see illustration below).

The illustration on the left shows loading efficiency percentages for identical surface areas, by profile of anchor. As a generalization, the Platipus system can be expected to either hold greater load capacities or require fewer anchors to achieve the same load holding capacity, by comparison to alternative, similar-sized anchoring systems.

We also contend that the Platipus anchors have much better driving characteristics than any other anchor, meaning they are quicker and easier to install.

Other anchors that might appear to be similar to Platipus often turn out to be variations of plate anchors, cut into a wedge shape or cut and bent to have “wings”. In our experience, the performance of these anchors is in no way comparable to Platipus anchors.

 

 

Q9.Is the frustrum cone permanent?

A. Effectively - yes, dependent on the component materials. As mentioned above, the materials for a Platipus anchor systems can have a lifespan of up to 100 years or more. The frustrum cone formed in the soil by the anchor system will have the same lifespan as the system materials. The only way for the frustrum cone to be made ineffectual before the lifespan of the materials expire would be:

1. Earthquake, landslip along a fault line or other disaster incidents.
2. If an excavator dug right through the middle of the cone, or dug out sufficient of the cone’s volume to reduce the load to below the required level.

With respect to the first point, for the cone to be seriously affected by a catastrophic event, it is almost certain that the event would have to be sufficiently severe for the anchored structure to be seriously damaged. In that case, the structure would have to be repaired/replaced and new anchors installed, as would be necessary with any other anchor types in the face of disaster situations.

With respect to the second point, it is possible that a mistake like this might occur, unless proper precautions are taken.

To better understand why additional embedment is a simple way of protecting against accidental de-rating of an anchor, it is helpful to consider the stress distribution of a Platipus anchor. Typically, a Platipus anchor will have dissipated 80% of its stress concentration at the anchor plate within a relatively short distance (equivalent to three times the width of the anchor plate) along the axis of the load.

In fact, the stress contours in front of a loaded anchor can be thought of as being similar to the rings of an onion, the soil supporting the stress being a very short distance in front of the anchor plate. (The multi-helix screw anchor is another example of stress dissipation over very short distances. It is the short dissipation distance that allows several plates to be used on the same rod with the ultimate load being proportional to the total of all the plate areas.)

To more clearly illustrate the implications of the above, consider a Platipus type B06TC anchors embedded at about 3m and loaded to 100kN. It gives a loading at plate of 2,198kN per m2 and 600mm along the tendon axis the soil loading has reduced to 440kN per m2. Therefore, excavation would have to be extremely close to the anchor to affect its ultimate duty. If the anchor has been embedded an extra metre as a precaution against inadvertent excavation then:

? The excavation has to be greater than 1 metre deep above the anchor before the “real” surface of the frustrum cone is even touched; and
? The excavator has to dig out all of the cone constituent material directly above the anchor for a further distance of 2.4 metres (making an excavation 3.4 metres deep directly above the cone) and in a circle of about 6.8 metres diameter around the installation point before 20% of the load capacity is removed. The probability of this happening is remote, especially if even the most basic precautions are taken to record the position of the anchor installation and/or mark the anchor rod.

Note that the same factors remain valid whether the anchor has been installed vertically or horizontally.

Ultimately, the whole issue distils to a matter of establishing a proper risk management strategy.

In assessing the most appropriate risk management tactic against the possibility of inadvertent excavation of critical cone area, a crucial consideration is how much of this part of the cone’s volume will have to be removed before the load will fall below the required minimum. Further, what is the likelihood of this occurring?

Obviously, in areas deemed very high risk, larger safety factors could be included in proof loading specifications (i.e., the load required could be over-specified) to protect against loss of critical cone volume and/or the (hypothetical) one metre extra “protective” depth mentioned above, could be increased. Conversely, in low risk areas, it would probably be unnecessary to include any “protective” element in planned embedment depth at all.

Q10. How close together can anchors be installed?

A. See the above question on the permanence of the frustrum cone. This makes clear that any intrusion by another anchor that would affect the carrying capacity of that anchor would have to be almost to the extent of one anchor “sitting” on top of the other Theoretically then, there is little need to separate the anchors by any great distance.

In practice the main consideration in anchor positioning is to avoid the anchors clashing with one another as they are driven into the ground (e.g, an anchor head hitting the anchor rod of another anchor could sever the rod). As a rule of thumb, we recommend that anchors should not be placed any closer together than 750mm (ideally 1.00m) at point of installation.

It is not always possible to locate the anchors 1m apart horizontally and in some instances the best solution is to locate them 1m apart vertically or in an appropriate combination of horizontal and vertical placement.