Cased Secant Piling (CSP)
Secant piled walls are generally a preferred solution for inner city projects. The reasoning is that they can be more flexible in shape and a compact operation when compared, for example, with diaphragm walling (this also requires a bentonite plant).
The interlocking piles of a secant wall can also form a closed structure to act as a barrier in water bearing soils.
The CSP system has been developed to combine the more cost-effective CFA technique with temporary casings that are more traditionally associated with rotary bored piling methods.
The CSP system generally has the following advantages:
- Better tolerance than an uncased CFA secant wall.
- Better ultimate appearance and reduced overbreak than an uncased CFA secant wall.
- Speedier operation than the more traditional ‘kelly / casing’ rotary bored pile method.
- Reduced risk of ‘flighting’ in poor soils than a standard CFA system.
- As it is a cased system; it reduces the risk of distress to adjacent structures in certain soils like sands or gravels.
In general terms, whilst the CSP process does have limitations with respect to diameter and depth, it will generally give the client a better assured product in terms of vertical tolerance and visual appearance.