Steel Intensive Basements

Steel sheet piling provides an economic alternative to reinforced concrete for the walls of a basement or underground car park.  In many circumstances temporary sheet piles were used to provide temporary earthworks support to enable the RC basement walls to be constructed against the piles.  However this was an economic use of the piles.  The ideal solution is to still use the piles for the temporary case but instead of the piles becoming redundant they are utilised to provide the permanent basement wall construction.

Although the design of a permanent retaining wall is more onerous that a temporary one, most basement walls are propped by the basement slab and ground floor and so the final design case is less than the temporary.  This usually means that the piles can be shorter in the permanent case, and this also opens up the possibility of the excess length being used to carry permanent vertical loads.

Watertightness is often required and sheet piling can produce a watertight solution for all grades of basements. Firstly the pile clutches can be welded from top of pile to underside of the basement slab to produce a watertight joint.  The joint between the sheet piles and the concrete basement slab can be made watertight by welding a steel puddle flange, consisting of a 100mm*10mm steel plate, to the piles at mid slab and applying a hydrophilic sealant to the plate.

The concrete basement slab can be positively connected to the sheet piles by either welding some of the reinforcement to the piles or using shear studs welded to the piles in a set grid pattern.

For underground car parks and storage areas in basements the sheet piles are often left exposed with just a simple coating of paint applied.  If a better aesthetic finish is required there are several options.  A blockwork wall can be constructed in front of the sheet piles or a thin skin of concrete cast, say 100mm thick at the pile face, with a steel mesh for nominal reinforcement.