Sheet piling is a method of deep foundations, which can be used in either the permanent construction of basements or temporarily for an excavation where foundations are being built.
We’re going to take a brief look at exactly what sheet piling is, and some of the things it can be used for.
What is Sheet Piling?
Sheet piling is the use of sheets, (usually made from steel, although timber or reinforced concrete could be used too), which are driven into the ground to retain soil and provide excavation support, and are linked together using interlocked edges.
Their extremely tough steel material and the interlocking system (along with optional sealants) means that sheet piling is extremely earth and water resistant.
For these reasons, steel is by far the preferred material, although timber may have its uses in temporary structures, and concrete is often used in marine structures.
They’re also a very sustainable option, as they are made from recycled steel, and because of their very long lives, they can be reused as many times as needed.
One thing to bear in mind is that there are two types of piling, ‘cold rolled’, which is less expensive but gives less resistance, and ‘hot rolled’, which is the favoured option and gives better resistance.
For more information on sheet pile walls and their advantages and disadvantages, check out this post from The Constructor.
How is it Installed?
Before installation can take place, it’s always important to check that the piles themselves have been checked for straightness, cracks and that the interlocking components are all in good working order.
The piles are then driven into the ground using both vibratory and vibration-free rigs, depending on the situation, and whether or not there are any environmental factors to take into consideration.
For example, it the soil is too hard or dense, then an impact hammer may be used, or a hydraulic hammer can be used when vibrations need to be kept to a minimum.
They’re driven into the ground in sequence to the specified depth along the planned excavation site, forming a secure wall for permanent or temporary lateral earth support.
If extra support is required, anchors and other props can be used too.
Care needs to be taken to monitor the piles as installation takes place, as they have a tendency to deviate from a vertical plane and lean sideways, or they may be unable to penetrate to the desired depth due to obstructions, in which case partial excavation or a water jet may need to be used to clear the way.
What is it Used for?
Sheet pile walls have a number of uses, both temporary and permanent. They can be used to support excavations for various underground constructions such as underground car parks, basements, pump houses, foundations, cofferdams, seawalls and bulkheads.
As an example of how sheet piling is commonly used to provide temporary support to enable permanent works, check out this case study of a basement in London, from Sheet Piling UK.