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What is the load capacity of Helicas - 2

24 December 2023

More things to take into consideration when sizing and prescribing Helica foundations

In addition to the aspects and conditions already presented above that influence the load capacity of our Helicas, there are a few more things to take into consideration when sizing and prescribing the Helicas.

Our foundations are formed by slender elements in the ground, with a large ratio between their length and diameter. This can lead to buckling phenomena, but of course the occurrence of these phenomena in the material also depends on the geotechnical conditions of the installation. An Helica may be very capable of resisting a load mechanically, but if placed on soft ground its capacity may be drastically reduced due to buckling. According to some bibliography, all soils that are not fluid can provide sufficient lateral restraint to Helicas as long as they are braced at their top. To be considered braced, they must have their top connected to two beams in two perpendicular directions or, if they are connected to just one beam, have two Helicas at the same connection point. If there are no beams at the top, there must be at least 3 Helicas at the same connection point.

There are many situations where our Helicas extend above the ground, going from foundations to visible columns. In these cases, it is necessary to treat our foundations as columns and check their buckling, in accordance with applicable regulations. The section of the Helica below the ground, in these cases, must also be considered for the length to be analyzed for buckling. In a simplified way, if the ground is firm we can consider a length of 1.5m below the ground or, if the ground is soft we can consider 3 meters below the ground. For this situation, we can consider soft ground to be all those that have a number of SPT hits between 0 and 5. As an example, for an Helica P2571, in the case of having beams in two directions at its top and being installed on firm ground, we can have a load capacity, just for the buckling phenomenon, of 28 tons, while if it is the continuation of a 3 meter high column and is placed on soft soil, its buckling capacity can be only 2 tons.



When prescribing the elements and method of installation, it is necessary to take into account that Helicas, like any other foundation, experience vertical displacement when the load is applied. This displacement is greater the smaller the soil capacity and the smaller the diameter of the pipe to be used. Using safety factors of 2, and taking into account that the Helica helix that resist the load capacity are found in soil extracts with SPT impacts between 20 and 40, we can expect deformations between 13mm and 25mm for service loads.

The load tests that Helica carries out continue to provide useful information to improve calculation methods and justify the formulation.

More information, please contact Helica team.

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09 September 2023


What is the load capacity of Helicas - 1

Check how the load capacity of Helicas is determined using geotechnical parameters

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