Combined walls

Combined walls

Steel sheet piles can easily be combined to form special arrangements and create systems with large bending resistance. Combined walls built up with box piles (or HZ-M, or steel tubes) and standard sheet piles are one of these solutions.

The primary piles, or “king piles”, of combined walls can also be used as bearing piles. and can bear high vertical loads, e.g. crane loads. The intermediary sheet piles act mainly as soil-retaining and load-transferring elements.

The equivalent elastic section modulus W_sys per linear metre, respectively per linear foot, of a combined wall is based on the assumption that the deflections of king piles and intermediary steel sheet piles are the same, leading to the following formulas

Combined walls built up with CAZ box piles and standard double AZ sheet piles:

• Combined-AZ
• Combined-AZ-800
• Combined-AZ-770
• Combined-AZ-750
• Combined-AZ-700

There are several combinations possible to achieve high bending moments and moment of inertia.

Notes:

• the equivalent elastic section modulus shown in the tables is for the element that takes the largest stresses (lowest equivalent section modulus of the system);
• if the king piles have a different steel grade than the infill sheets, then the stresses in both elements have to be checked separately (with two different equivalent elastic section modulus!);
• the infill sheet piles AZ are usually lighter and shorter than the king piles;
• the fabrication of the CAZ box piles is quite expensive and time-consuming. It should only be done by experienced welders, based on a specific welding procedure.

Combined walls built up with U-type box piles (CAU-2 / CU-2 / CGU-2) and standard single, double or triple U-type sheet piles. There are several combinations possible to achieve high bending moments and moment of inertia.

• AU: 750 mm wide piles (Belval)
• PU: 600 mm wide piles (Belval)
• GU: 400 and 600 mm wide piles (Dabrowa)

These solutions are selected most often for retaining walls with a bearing function, where the box-piles increase the rigidity of the wall and/or the vertical bearing capacity, and are usually longer than the infill sheet piles.

Notes:

• the equivalent elastic section modulus shown in the tables below is applicable to the element that takes the largest stresses (lowest equivalent section modulus of the system);
• if the king piles have a different steel grade than the infill sheets, then the stresses in both elements have to be checked separately (with two different equivalent elastic section modulus!)
• for double and triple piles, the section properties shown in the table is based on the assumption that the common interlocks are either crimped or welded.

Combined walls with steel tubes are an alternative to the HZ-M/AZ system. Tubular piles are the main retaining elements of the combined wall (king piles), carrying horizontal loads from soil and water pressures and vertical loads from the superstructure or anchoring system. 

The intermediary AZ sheet piles (infill sheets) transfer the horizontal loads from the retained soil and water to the tubular piles. Note that infill sheet piles are usually shorter than the king piles.