A large problem facing the development of Solar Farms in Australia is the presence of reactive clay soils. These are soils that consist of clays and can have severe medium-to-long term impacts on the foundation systems of Solar Farms.
The clay soils heave and shrink overtime from being wetted and dried. This causes an effect known as ‘hydraulic jacking’ which can lead to the foundations and supported structures of a solar farm to quite literally eject from the soil. During severe wind events, these structures can become very dangerous as they take flight across various areas of the solar farm.
Common solutions for these soils to this point have mainly consisted of either pre-drilling to allow the installation of extra long galvanised H-Beams or, using various end bearing screw piles. The idea is, by making the H-Beam piles longer, they may be installed to depths that are non reactive and can therefore better survive the applied hydraulic forces from the shallow reactive areas above.
The problem is, pre-drilling disturbs the soil around the foundations, accelerating the process of hydraulic jacking through increased water ingress. The increased water can create a sump that amplifies the natural clay soil suction processes. Once the reactive/hydraulic skin friction forces in the upper shallower area becomes greater than the passive skin friction strength at the base of the pile, the H-Beam piles are no longer able to resist being pulled up by the above jacking forces.
Screw piles face their own issues due to their single edge helical design. This design makes it near impossible to maintain top-of-post positional tolerances during installation due to the piles ‘walking off’ position. Screw piles can often be pulled during installation as a method of controlling the pile position and when the pile encounters hard underground layers, they can have insufficient torsional capacity to reach founding depth.
So how can this problem be solved?
We set ourselves the goal of answering the reactive soil problem for Solar Farms by creating an innovative product like no other. We knew this new product had to have the bending moment strength and flat sided nature of H-Beam piles, while providing the anchor-like end-bearing vertical load capacity of a screw pile.
It was after two years of R&D and testing that we were finally able to unveil the ‘Solar X Blade Pile’.
The Solar X Blade Pile is a square hollow section, internally bottom-driven displacement pile that features a dual-blade, screw-in design. The pile is installed through the use of a unique forged steel drive hub. A solid steel drive shaft is inserted into the pile and connects into the drive hub socket at the base. The drive hub screws the blades into the ground, resulting in the pile being pulled down to the required founding depth.
Further images and video of Solar X Blade Pile testing can be viewed in our gallery.
With this new exciting product, Solar Farm developers are now able to confidently approach aggressive reactive clay sites with a foundation system that eliminates the need for pre-drilling and simply works.
If you would like to read more about how we can help Solar Farm developers, EPC’s and array suppliers, visit our ‘work with us’ page or contact us today.
Written by Solar Pile International.