(i) They have a lighter weight for a required load-bearing capacity.
(ii) They can be used in longer lengths and extending them by butt welding is relatively simple. Similarly excess length is easily cut off.
(iii) They are more resistant to handling and driving stresses.
(iv) They can have good resistance to lateral forces, bending stresses and buckling.
(v) They are particularly useful for marine structures (piers, jetties, etc.) above water where the piles may be subjected to impact forces, ships docking, etc.
The disadvantages of steel piles are:
(i) There is a need for corrosion-protection.
(ii) The pile cost per metre run can be relatively high.
(iii) There are fewer piling sub-contractors competent to carry out the work.
(iv) There is a tendency for H sections to bend about the weak axis when being driven – the resulting curved pile has a lower bearing capacity.
The use of stones or large gravel in piling is now a well-developed technique. The authors have been involved in extensive use of this form of piling for many years.
The method is used mainly as a geotechnical process to consolidate and compact soils and/or to improve their drainage. The technique is discussed in detail previously and reference should be made to that chapter for further information.
Table 14.1 Steel H piles – dimensions and properties
Table 14.2 CAZ box piles – dimensions and properties