Standard pile driving techniques for steel sheet piles includes impact driving, vibro driving, and hydraulic pressing. Are these methods applicable to Vinyl Sheet Piles or sometimes called PVC Sheet Piles, Synthetic Sheet Piles, and Plastic Sheet Piles? The answer is YES!
As earlier claimed by some plastic sheet piles manufacturers, standard piling rigs and equipment can be used for driving FRP and Vinyl Sheet Piles. Though vinyl sheet piles has enormously lower elastic modulus compared to other materials especially steel sheet piles, they have been tested and found suitable for common driving techniques and proven to be stiff enough for different means and areas of installation. At present, they are being utilized in huge quantities in catering the increasing project needs in different Regions. Vinyl sheet piles are becoming popular in construction of bulkheads, seawalls, and cut-off & containment barriers.
Report TRL533 by TRL Limited (USA) on 2002 has illustrated the success of driving plastic sheet piles as follows:
i) The US Corps of Engineering used a 3400lb vibrating hammer and achieved a driving rate of two 16 foot sheets in 90 seconds.
ii) VJE Construction (USA) used a crew of 8 with a 90lb air hammer to drive 2,100 linear feet of vinyl piles at a rate of 250 linear feet per week.
iii) At Long Bay Pointe Marina (USA) 3,300 linear feet of vinyl sheet piling were driven using a vibratory hammer to drive through clay, rocks and tree stumps (Chesapeake Angler Magazine).
iv) In Holland and the USA water jetting has been used to install plastic piles in some soils.
Still from the above-mentioned report, a case study was also featured wherein an actual visit was made to observe plastic piles being driven at a spillway. A very important observation was recorded as below:
The flexibility of the sheet piles was such that significant bending occurred during driving of a single pile. This was not such a problem when the piles were driven as a pair and further improvements could probably have been made by providing more support to the piles.
It appears that driving plastic sheet piles and other sheet pile materials has no difference at all.
For a successful installation in hard, dense surfaces, and in ramming long elements, the use of special guide bars called mandrels or jigs is advised. Side or front mandrels work best. This is a steel element with shape identical to the rammed vinyl sheet pile. Mandrel length must match the length of the rammed PVC elements.
There are 3 main mandrel types that ESC recommends, all of which are specially constructed of steel following the general profile of the PVC sheet pile being driven. They are sleeve mandrel, side mandrel, and cutting mandrel.
Like any other material, vinyl sheet pile’s drivability are enhanced by the used of guide structure or template. Many contractors recommend at least two templates be used in driving each pile or pair of sheet piles. Guides or waling holds the sheet pile in place and templates should also be used to obtain correct plumb of the sheet pile wall.
Being lightweight, vinyl sheet piles may face difficulties in penetrating difficult ground conditions such as very compact, cohesive or coarse granular soils. In these cases, jetting is used to ease the driving activity. This process creates pressure directly under the installed sheet piles, which loosens and removes the soil or the obstacles. Special water or air ejectors are applied in this technology.
And lastly, as an ultimate plastic sheet piling solution, some manufacturers have also managed to develop special rigs such as Japan’s hydraulic “Silent Piler” which minimize stresses on the plastic sheet piles which are obviously less robust than steel sheet piles. In this scenario, most obstacles and difficulties in driving plastic sheet piles are most likely eliminated.