The Product

The Earthbolt Mk IV Precast and Tilt-Up Concrete Panel Prop Safety Anchor was designed as a temporary foundation system to replace traditional and costly cast in-situ concrete strip and bored pier designed footings. Using several industry engineering specialists in various disciplines the design agenda was simple; to create the safest and strongest temporary foundation system to resist movement under maximum wind loads.

The design process and testing was not as straight forward. There had been earlier attempts at similar products however their designs were not totally focussed on our industry’s safety or compliance requirements. Their first attempts resorted to adapting existing products, for example a light pole foundation pile by changing the top plate to accept the brace or prop footing. The other issue was longevity where these products were not designed for multiple installs; thus they required monitoring and were only certified for a certain number of uses. We needed a product that could be easily maintained and could easily sustain multiple installations without compromising the integrity of its structure.

The patented Earthbolt design benefited greatly from not only learning from earlier designs and their faults but importantly it was purely designed from the ground up for precast concrete panels to accept lateral forces imparted by wind loads. The anchor was subjected to stringent geotechnical testing to replicate worst case loading conditions for combined uplift and lateral loads in soils far less cohesive than would be ever be encountered under normal working conditions.
For industry compliance the design focussed on a widest top plate possible along with only 2 propping attachment points. The 530mm width of the top plate was crucial in bringing the brace angle to within the +/- 5 degrees to the perpendicular in line with the recommended angles outlined within the National Code of Practice for Precast, Tilt-Up and Concrete Elements. The Earthbolt product then adopted an assembly that included a lateral stabilizer plate that with a width of 420mm and a length of 600mm that once driven into the ground engages a large passive soil wedge to resist lateral movement and moment loading dissipating the energy through the cohesive nature of the surrounding soil.

Not only was the lateral stabilizer assembly designed and tested to provide maximum strength under immense loads through its design reacting with surrounding soil resistance, the stabilizer plate is connected to a failsafe collar further down the shaft assembly ruling out the possibility of any catastrophic event with structural failure. The structural integrity of the Earthbolt product starts with its 1350mm pile shaft; a seamless boiler grade steel 90mm OD pipe manufactured to AS1163 with a minimum yield strength of 350mpa and tested to an ultimate axial compression of 460kN.

The geotechnical principle of the helical safety anchor relies crucially on its helix design, giving resistance in both uplift and compression loads. Thus not only its overall width but also the pitch of the helix is important to its integrity. The Earthbolt products reusable design demanded great strength from the helix component and after hundreds of tests a width of 320mm was chosen to be manufactured from 16mm high grade steel with a heat treated leading edge. This was important for installations as in trying to minimize the pitch angle of the helix for uplift strength it also decreased installation speed.

The ultimate relationship between installation torque and capacity is considered to be the greatest attribute of the helical foundation design. As a helical pile is introduced to the soil the resistance increases as does the required energy or torque to achieve full installation. The latest torque monitoring equipment and testing equipment certified by NATA was used in establishing the combined ultimate moment capacity of the Earthbolt safety anchor. The Nm of torque applied through testing in various soil conditions have determined a certified maximum WLL of 52kN capacity with braces connected at 60 degrees.

The product was designed and tested for 2 brace footing connections installed perpendicular to the panel join with a setback to achieve a 60 degree angle for maximum strength. This is where its advantage lies in that its total design mechanism was focussed on one industry and one use. The MkIV Earthbolt anchor achieves all its design agenda requirements and more with structural longevity, working load capacity, ease of maintenance and a 100% safety record. But also in that its design loses none of its load integrity even with prop angles skewed from the perpendicular at more than double the recommended National Code angle; because it was engineered and certified for this thanks to the unique load capabilities of the lateral stabilizer plate design.