ProLock® and MultiLock®

Plastic Sheet Piling Suggested Applications

Plastic piling has proven itself in many diverse applications:

Erosion Control, Drainage channels and Bank Retention

With the prolific use of timber retaining walls, either through willow bank construction, Nicopsan or the use of gabions systems with coir rolls; it is clear that these methods have merits appreciated throughout the industry.  The main perceived benefit, particularly Nicospan, is short term cost savings and also the natural aesthetics generated as plants grow through as the system mature.   However, these natural systems do not have the longevity of engineered sheet piling, the later of which can create a fully supporting system that will last 5 times longer, if not more.

APE appreciates that traditional sheet piling, including the older designs of plastic piling do create a very artificial appearing system.  Deep and repetitive corrugations which provide strength, do detract from the natural appearance of a waterway.  However, no "green engineering" technique to date produce the consistent level of viable long last solutions.  That stated APE have spent considerable resources seeking out products that can provide the best of both, and the MultiLock is definitely one product that meets this criteria.  It still has repetitive corrugations, but very shallow corrugations as it derives its strength from is full sectional shape, most of which is hidden in the bank or beneath the capping.   It is a full "green" solution in that it combines recycling with sustainability, whilst still maintaining longevity.

Curvy or straight!

APE's strategy in terms of its plastic piling is to offer an adoptive approach, where other methods or materials have merits, we seek to include them, not replace them.  Consider a Nicospan system, a geotextile supported each metre by a 100mm diameter post, the MultiLock can use an identical sized post every 25 cm.  Why not use both, the MultiLock just beneath the water level, where its strength and erosion control is unparralleled, and then thread the Nicospan through extended timbers above the MultiLock.  These timber supports could also be used in conjunction with coir rolls or bundles, either threaded around or directly attached!

That way you combine a structured approach with a method that will permit growth, maintaining that sought after natural appearance.

Traditional applications are clearly waterways related, such as retaining walls, seawalls, erosion and scour protection.  These applications benefiting from the increased longevity of the product and its resistance to natural causes of deterioration such as oxidation or biological attack.

Common Concerns

The two common concerns surrounding plastic piling, particularly those that have attempted installing older designs of plastic piling are:

• How do I install it?  Plastic is very flexible compared to steel, will standard piling equipment install them the same way?
• With the increase in the use of the canal and riverway infrastructure, how can plastic tolerate impacts from boats, surely they would get damaged and compromise the integrity of the bank support?

Installation

It is envisaged that the flexibility of these products will permit a wider usage within waterways, as the system requires much shallower installation, it can be used in much hard ground conditions, where traditional plastic piling could not be driven, but where steel tubes or timber posts can easily. 

In many cases, until now, not one manufacturer of plastic piling has provided any satisfactory answers, most will simply tell you that yes, standard equipment will drive them no problem any length. These comments are made without any true appreciation of piling equipment designed for installing steel.  APE has spent considerable resources designing interfaces and mandrels (the latest University project conducted by APE with Cranfield University, confirms our commitment).  These were all needed for even installing the shortest lengths of plastic piling! 

With the advent of the MultiLock, APE can concentrate its activities on driving substantial lengths as required for cut-off wall applications, through the provision of novel mandrel designs not to mention the release of the APEX Hammer!

Vertical or raked!

Look at these photos, it is clearly visible how this system is installed - the plastic piles are simply pushed or vibrated a short distance into the ground, and then timber posts are driven to depth to locate and support the wall construction.  It is well established within the industry how timber posts can be driven.

Impact resistance

Some manufacturers have conducted Charpy or IZOD impact testing on the material, equating these methods to the impact likely to be produced by boats.   MultiLock plastic piles will have an internal reinforcement, either timber or steel.  Any impact or collision energy is clearly better tolerated, as it is transferred through the wale, into these reinforcements.

Further as retaining loads may vary along a run of piles, despite walers transmitting the load across the wall, there is clearly an additional facility with ProLock MultiLock to locally increase the bending moment as required. 

Timber or Steel

In the case of the MultiLock sheet, very light applications can simply use the plastic pile, higher loads the MultiLock plus a single timber pile, higher loads still two timber piles.  The concept is extended with ProLock as it can and has been used with steel tubular piles!

Flood defences and Landfill Cut-off walls

Containing or excluding water is one of the key applications of plastic sheet piling, it does not rust like steel or rot like wood.  Therefore it is ideally suited to water based applications.  The ProLock MultiLock range is perhaps best suited to retaining walls and bank support, since its concept is one of minimising sheet length to reduce overall cost, without reducing product quality.  Within a cut-off application such economy is not an option since the pile needs to be driven to depth to provide a cut-off.  That stated the MultiLock and ProLock do have certain advantages within this applications.

The novel symmetrical shape of the MultiLock profile means that this pile is naturally more rigid and therefore would more efficiently drive using a vibratory hammer, than conventional plastic piling.   Within these applications long lengths around 4-7 metres need to be installed, all plastic piling is flexible to an extent, however only the ProLock and MultiLock can be driven with steel tubes or timber posts. 

In most applications the steel tubes or timbers are required for additional load bearing.  In this application there is only one load, that being the load during installation, the use of internal timbers or tubes will rigidise internally the plastic pile making longer lengths easier to drive without full pan mandrels such as the Stabcat Stommper.  

For areas where the works are simply to build up existing flood defences, then this system clearly has the main installation advantage.  This product has been used by major Civil Engineering Companies and also home-owners and onwers of caravan parks.  The product appeals to main stream civil engineering since it is a quality well engineered product, it appeals to less technical users as it is so easy to install, making it ideal for domestic usage.  In Holland, there are even examples of it being used domestically for ponds, fencing as well as building up local flood defences when garden end adjacent to water courses.

Retaining Walls and Embankment Support

The ProLock MultiLock product range is better suited to permanent works rather than temporary, and would represent an ideal product from carriage way embankment slope support and stabilisation. The Transport Research Laboratory (TRL) conducted major research into the use of Plastic Piling and has published a report into their findings, Guidance on the Structural Use of Plastic Sheet Piling in Highway Applications (ref: TRL 533). A copy of this research is available by contacting the TRL 

Prior to the release of this report APE met with Dr Derek Carder, to provide information on installation methods, the concept of the proposal was to install tiers of 4m plastic piles.  However at that stage, it was a concern whether 4 metre lengths of traditional plastic piling could be handled.  These 4 metre piles would need to be driven 3 metres to provide support for a 1 metre retaining wall, within each tier. 

MultiLock can do exactly the same thing using 1.5m sheets and 2-3m timber piles, so reducing the length of pile that needs to be handled, and reducing the cost of the project; consider 1 km of 4m cheap standard piles, hard to handle, difficult to drive and regardless of the selling price it will never be as cheap as a pile twice as wide (less piles needed) and half the length!  Further because of the short lengths being used less sophisticated pile drivers are needed, even a small vibratory compactor would suffice!

Ditch Blocking (Grip Blocks, Plastic Piling Dams)

This plastic piling product is truly economic when used to its full advantage and that is used in combination with other elements.  It therefore looks to be the first product that can reduce the cost of ditch blocking (grip blocks) without compromsing on the quality of the sheet.  In terms of manual handling it is clear that whilst these sheets are heavier per metre than those sheets used at present, this is easily offset against the far shorter length required. 

Consider the folllowing picture showing traditional plastic sheet piling used as a dam, but having to be subsequently braced using a timber retaining structure.  This structure is exposed to the elements and will degrade, had this application used MultiLock, then the timber support would have been internal, not only a neater finish, but protected from the elements by the pile itself.

First Trial Installation with Scottish Natural Heritage

Installed and the dam begining to fill 1 day after

The other side of a full dam