Patrick Henderson foundation is a technology widely used in the States, with thousands of installed foundations, but far less common in Europe.

It’s a patented solution that consists of a large diameter, cast-in-place annular pier, with an average diameter of 4.5 m and a depth of about 9m, depending on the soil conditions and the loads.

Two concentric corrugated metal pipes (CMP) form the interior and the exterior of the concrete hollow annular pier: between the 2 corrugated pipe, an anchor cage is positioned and the bolts are post tensioned to ensure that the concrete of the pier remains always compressed.

The hollow interior of the pier is filled first with 1 m of concrete, than with uncompacted soil and finally with a 35cm thick structural slab.

Basically the P&H foundation works a lot like a beach umbrella.

Among the advantages, a smaller footprint and less material consumption: as an order of magnitude we are talking of approximately 160m3 of concrete and 20Tn of steel.