Helical Piles are steel shafts with a series of low-pitched circular steel helical plates welded at strategic positions along the shaft. The plates give the foundation both tension and compression bearing capacity which enables them to be used for a wide range of applications across many industries and sectors.
The piles can be connected in groups using a steel load transfer grillage and are screwed directly into the ground by machine-mounted hydraulic or electrically powered drilling equipment.
ScrewFast’s GRIP® Pile technology is a hybrid micropile, used to transfer load through soft soil into shallow rock, or very hard soil. A GRIP® pile consists of a shear tube made of steel CHS which encases the pile through the soil and a rock socket, which anchors the pile into the rock. The rock anchor comprises a central reinforcing rod encased in grout with a sacrificial drill bit at the toe. The shear tube is installed first – usually by vibrohammering – and increases the piles resistance to lateral loads.
GRIP ® Piles
GRIP ® Piles
Helical piles can be installed with a wide range of hydraulic or electrically powered drilling equipment. The helical piles, which consist of a steel shaft which has a plate welded to the exterior surface, is turned by the chosen equipment directly into the ground to the designed depth. They take a very short time to install; usually under an hour due to their ability to distribute weight far below the surface. ScrewFast have the capability to design and build helical piles to accommodate single pile unfactored loads of 750kN in compression and 500kN in tension, which is unparalleled in the UK.
A shear tube is driven through the softer topsoil to refusal or design length and embedded within the harder sub strata. A ScrewFast GRIP® pile bar with sacrificial drill bit and spacer attachment is drilled through the centre of the shear tube. Further pile bar sections with spacers are attached until the design depth is achieved. In some cases, the cavity may require flushing with grout during drilling.
Once the design depth is reached, grout is pumped through the centre of the pile bar and out through the holes in the sacrificial drill bit. The whole cavity and shear tube are filled with grout. An intermediate connection piece is added to provide strength and levelled in preparation for the substructure. The grillage is then landed onto the piles. The grout connection gives 75mm tolerance in any lateral direction. The grillage is bolted to the piles and grout is poured into ScrewFast’s patented grout boxes to secure and protect the connections. The structure can be loaded after a minimum grout strength of 25MPa is achieve, which is usually around three days.