FAQs
A Hulk Earth Anchor is a geotechnical anchor designed for holding tensile loads. Hulk Earth Anchors can also be referred to as ground anchors, mechanical anchors, or more specifically, percussion anchors, driven anchors, or tipping plate anchors. If you have not read it already read, please see How Hulk Earth Anchors Work
Only if the anchors are placed in soil which is affected by the weather. A responsible anchor design attempts to place anchors to a depth where the soil is unaffected by weather and seasonal variations. Or if soil variation is unavoidable, then the anchor must be sized and proof tested for the worst case soil condition.
Not unless the anchor depth is one that places the anchors into soil that is unstable or seasonally variable. In general, greater depth usually results in greater capacity, but not always. In some cases loose wet soil can exist below stable competent soil, so increased depth can be a detriment. Anchors should be placed into soil that will not be subject to freeze thaw cycles.
A conservative rule of thumb is to place the anchors no closer than the depth to which they are installed, but in many retaining wall installations anchors are placed as close as 1.5m x 1.5m rectangular pattern. Account for a 25% load loss factor which represents a reasonable maximum interference factor as the anchors cannot practically be placed any closer together. If interference of anchors is a concern then this is a reasonable way to account for this effect.
It depends upon the soil, and the required depth. In very hard soils, the 100mm auger is a good choice for the HG-100. The anchor will easily pass down the hole, yet will still lock in place against the sides of the hole. For medium soils a 75mm auger may be a better choice, or it may not be necessary for an efficient installation. In either case, if a pilot hole is used it is important to back fill the hole with the drill cuttings after the anchor is placed, but before load locking. It is wise to back fill and compact the soil (usually done with the drive steel) prior to load locking because it will help the anchor to tip and lock. Virtually every anchor installation is different, but the 100mm diameter pilot hole is a good general choice for pilot holes for all HULK HG anchors. Because every installation is unique, there may be better choices for different soil conditions, drive depths, etc.
This does happen occasionally in some hard slippery soils where a pilot hole has been drilled. We have not had a report of this happening where the anchors were driven without a pilot hole. If a pilot hole is used it is wise to back fill the hole with the drill cuttings after the anchor is placed, but before load locking. It is wise to back fill and compact the soil (usually done with the drive steel) prior to load locking because it will help the anchor to tip and lock. We have seen some installations where the drive steel was placed backwards down the hole to hit the scoop of the anchor to start it to tip and lock. We have had some installers sharpen the scoop with a grinder to help it grab into hard soil. It is generally accepted by most installers that the anchors lock better if the initial pull is done at as fast a speed as possible.
Yes, HULK anchors work very well in frozen soil, but a pilot hole is usually a requirement. If there is only 1m or less of frozen soil, then the anchor can be driven through the frozen soil into the underlying non frozen soil. If the soil is frozen for the entire installation depth then a pilot hole will be required. Beware, frozen soil is very tough and may require heavy duty mechanized drilling and driving equipment. Anchor capacities in frozen soil are very high as long as the soil remains frozen, but if the soil around the anchor thaws the soil will revert to its thawed, lower capacity state. If the soil is of good high capacity prior to freezing, then this is not as large a concern.
Soil with resistivity less than 3000 ohm-cm, pH less than 5, Chlorides greater than 1000 ppm, Sulfates greater than 500ppm, and poor aeration. The above soil parameters are obtained from chemical tests on soil samples.
The internal threads are actually protected by the galvanizing from the rod that is threaded into them. This was graphically proven on a utility guy anchor that was retrieved from an extremely corrosive environment complete with stray currents and aggressive soils. The anchor rod and shackle of the anchor were corroded to approximately 50 % of their original dimensions (the residual strength would have been about 25 percent of original). Disassembly of the shackle and the rod showed that the internal threads of the shackle and the external threads of the anchor rod had retained their original dimensions.
Grout is commonly used with HULK anchors to enhance holding capacity and to provide corrosion resistance at the expense of a more complicated installation. Typically a grout tube is attached to the anchor rod and grout is pumped through the grout tube to the bottom of the hole. This has historically provided good coverage of the anchor, shackle, and anchor rod, but there are many variables and care must be taken to ensure good complete coverage. A more detailed treatment of grouting anchors is available from Percussion Earth Anchors upon request.
Percussion Earth Anchors can provide a system of double corrosion protection by supplying galvanized anchor components that are painted. Installation methods are a bit more involved in order to minimize damage to the paint, but it has been specified by some Engineers and can be supplied. Contact your HULK distributor or Percussion Earth Anchors.